Corn, Sweet

Introduction

Sweet corn (Zea mays convar. saccharata var. rugosa) is a warm-season crop and one of the major vegetables grown in New England.  It is an extremely popular crop for roadside stand and farmers' market sales as well as for wholesale markets.

Sweet  corn grows on a wide range of soil types.  Early planting should be on light, well-drained soil in a warm, sheltered location.  Heavier soils are best for the main crop.  Plowing under corn stalks and cover crops to maintain high levels of organic matter in soils is recommended for best crop production.  Irrigation may only be necessary in dry weather, particularly on light soils, and especially as silking starts.

Types and Varieties

Sweet corn varieties are categorized by their genotype.  The most common types are normal/sugary (su), sugar enhanced (se), and supersweet/shrunken (sh2).  Other newer varieties include sweet breeds, synergistic, sweet genes, or improved supersweets which have a combination of genes.

su           "Normal" or "Sugary"

Standard hybrid sweet corn is a mutant type of corn that differs from field or dent corn by a mutation at the sugary (su) locus. This type accumulates about twice as much sugar than field corn.

se          Heterozygous Sugary Enhanced or "Modified Sugar" or "Everlasting Heritage (EH)"

se+        Homozygous Sugary Enhanced  

There are two distinct groups within the cultivars containing the "se" gene, which increases sugar levels above those found in "su" varieties.  The "homozygous se" or se+ cultivars have higher sugar levels in 100% of their kernels.  Cultivars that are "heterozygous se" have higher sugar levels in 25% of their kernels; the other 75% contain the normal "su" gene with lower sugar levels.  Thus, "se+" cultivars are usually sweeter than "se" cultivars.

  • Sugar conversion to starch is about the same rate as standard sweet corn.  Refrigeration is essential to maintain quality.
  • Isolation not required, but desirable. Note directions on seed tag label.
  • Kernels tender and creamy.
  • Tip cover weak on some varieties

sh2           "Super Sweet" or "Extra Sweet" 

  • Sugar content twice as high as standard sweet corn.
  • Slow sugar conversion to starch so quality will hold 7-10 days. Refrigeration suggested to extend quality.
  • Isolation is required from all other types of corn. Note directions on label.
  • Kernels can be somewhat tough or crunchy.
  • Does not germinate well in cold, wet soil.  Plant after soil temperatures exceed 65° F and be sure there is adequate soil moisture.  Adjust planting depth for soil conditions and soil type.  Seed of the "sh2" type is light-weight, wrinkled, and fragile and should be handled gently to prevent damage.

syn          "Synergistic"

These include synergistic or improved supersweets such as Sweet Breed and Sweet Genes.  These varieties have combinations of su, se, se+, or sh2 genes.  Synergistic varieties having the sh2 gene may be grown with other "Super Sweet" varieties, but must be isolated from "se" and "su" types to achieve best quality.

aug          "Augumented Shrunkens"

Augmented Shrunken sweet corns are a new type of shrunken corn types. They contain the "sh2" gene, but kernels of augmented shrunken are more tender, like "se" varieties.  Augmented shrunken varieties should be hand harvested because their tender kernels will likely be damaged by machine picking. These varieties need to be isolated from normal, "se" and synergistic hybrids. Additionally, they have the same seed vigor problems as supersweet varieties and should only be planted under optimal conditions.

MiraiTM    

MiraiTM sweet corn varieties carry two copies of all three sweet corn genes: su, se and sh2. They have all tender supersweet kernels and, like the augmented shrunken varieties, need to be hand-harvested. Mirai varieties also need optimal soil conditions for seedling establishment. Mirai types do not require isolation to avoid starchy kernels, but isolation from other sweet corn types will assure best quality.

Bt Hybrids

These are genetically-modified (GM) varieties that are protected from European corn borer, and to a lesser extent, fall armyworm and corn earworm caterpillars because they express the protein toxin of the bacteria Bacillus thuringiensis. They are currently available as super sweet (sh2) or as synergistic "TripleSweet" varieties, composed of 75% "se" and 25% "sh2" kernels. In the synergistic varieties, the Bt toxin is expressed in the "se" kernels, the stalks, leaves, tassels and fresh silk. Bt varieties are still susceptible to attack from flea beetles, cutworms, aphids, sap beetles, high levels of corn earworm and soil-dwelling insects. Bt seed costs more than the seed of other sweet corn varieties and currently comes with a list of resistance management strategies with which to comply. These varieties may reduce the time, energy and expense associated with insect control and may simplify sweet corn pest management. There are many other less obvious potential risks and benefits that may be associated with the use of this technology. GM sweet corn varieties, including all Bt varieties, are not allowed in organic production. Growers in Maine must be certified to grow Bt corn. Contact the Maine Board of Pesticides Control for more information. 

Sweet Corn Varieties
Variety Type Color Wilt Rust MDMV
Sweet Chorus (67) syn Bi L M M
Sweetness (68) syn Bi - - -
Latte (68) syn Bi M M -
Vitality (68) se Bi - - -
Espresso (70) syn Bi M M -
Mirai 308BC (70) mirai Bi - - -
Harris 1001 (72) se Bi M - -
Temptation (72) se+ Bi - - -
Reflection (72) syn Bi - M -
Cuppa Joe (73) syn Bi M M -
XTH 2170 (73) sh2 Bi M - -
Mirai 336BC (73) mirai Bi - M M
Sweet Rhythym (73) syn Bi M L -
Anthem XR (73) sh2 Bi L H -
Charisma (74) se Bi M M -
Fanstastic (74) sh2 Bi - - -
XTH 274A (74) sh2 Bi M - -
Sweet Ice (74) syn W M L L
Kristine (74) syn Bi M M -
Mystique (75) se+ Bi H M L
SC1102 (75) syn Bi - - -
Sparkler (75) syn Bi - - -
Mirai 301BC (76) sh2 Bi M M -
Awesome (76) sh2 Bi M - -
Luscious (77) se Bi - - -
Accord (78) se Bi - - -
Legion (78) sh2 Bi M M M
Pow Pow (78) syn Bi - - -
Essence (78) syn Bi M M -
Providence (79) syn Bi - M -
Montauk (79) syn Bi M - -
Delectable (80) se+ Bi M H L
Precious Gem (80) se+ Bi M M L
Primus (81) sh2 Bi M M -
BC 805 (82) * se Bi - H -
Jackpot (82) se+ Bi M M -
Silver King (82) se+ W M M -
Argent (83) se W H M L
Incredible (85) se+ Y H - -
Cameo (84) se Bi M M -
Silver Queen (94) su W H L L

The number in parentheses is the approximate number of days to maturity from seeding.

H, M, L indicates high, medium or low resistance or tolerance to the following diseases - Wilt: Stewart's wilt, Rust: Common rust, MDMV: Maize dwarf mosaic virus.

Other codes: mirai: mirai, su: normal sugary, se: sugar enhanced, se+: sugar enhanced homozygous, sh2: supersweet/shrunken, syn: has some combination of su, se and sh2 genes, Y: yellow kernels, W: white kernels, Bi: bicolor, *: Bt hybrid

Cultural Practices

Soil Fertility

Apply lime according to soil test to maintain soil pH between 6.5 and 6.8.

Less nitrogen fertilizer will be needed if legume sod was plowed down or if manure was applied (see Table 1, page 2 and Table 7, page 15). 

Apply no more than 80-100 pounds per acre combined weight of actual nitrogen and potassium applied 2" on the side and 2" below the seed as a band. Higher amounts of nitrogen and potash applied as a concentrated band may damage corn seed and young plants.

Plant Nutrient Recommendation According to Soil Test Results for Sweet Corn
  Nitrogen (N) Lbs per acre

   Phosphorus (P) Lbs P2O5 per acre

   Potassium (K) Lbs K2O per acre

Soil Test Results   Very Low Low  Optimum Above Optimum Very Low Low  Optimum Above Optimum
Broadcast and Incorporate 0 100 40 0 0 150 90 0 0
Band Placement at Planting 40 40 40 40 0-40* 30 30 0-30 0
Sidedress 60-90** 0 0 0 0 0 0 0 0
TOTAL RECOMMENDED 100-130 140 80 40 0-40* 180 120 0-30 0
*Phosphorus applications are recommended only for early-season corn sown in cold soils.
**Before sidedressing use a nitrate test to determine the need for additional N

Planting

Effective isolation is required in some cases with the present types of sweet corn on the market. Isolation is affected by distance, wind direction, time of pollen shed and silking, and blocking. From a practical standpoint, the same methods are needed as when separating white and yellow varieties. Field experience indicates isolation can be managed more easily than initially expected.

Plant early varieties 8"-10" apart within rows with 30"-36" between rows. Plant main season varieties 10"-12" apart within rows with 36" between rows. This requires 10-15 lb of seed/A (1-2 oz per 100 feet of row) or 17,500-26,000 seeds/A for early and 14,500-17,500 for main season varieties. Match seed size to seed plate. Read seed container or contact the company regarding appropriate plate sizes. 

First plantings are made in early April in southern New England and in May in northern New England.  Growers planting in cold soils run the risk of erratic germination and poor stands.  Avoid planting while soil temperature is lower than 55° F.  If soil temperature is below 60° F, it is advisable to plant treated seed.  If you are planting untreated seed, wait until the soil temperature is at least 65° F.  Most seed companies perform cold germination tests of their seed.  If in doubt about the suitability of a corn variety for early planting, ask your seed dealer about the low temperature germination and vigor of the seed. 

Clear plastic mulch raises soil temperature and can be used for the earliest plantings.  This can allow for earlier planting and provide corn 7-10 days earlier than non-mulched corn.   Apply fertilizer and herbicides, and plant seed before laying the plastic over seeded rows.  Two rows 18"-24" apart are usually planted under each strip of 5 ft-wide plastic.  To avoid plant injury, do not let temperatures beneath the plastic get too high (90° F or more).  When such conditions occur, or when the plants reach 4" in height, cut slits in the plastic to allow heat to escape and plants to grow through.  Remove the plastic completely by the time the corn is knee high to facilitate removal and permit cultivation.

Spunbonded row covers offer a potential three-way benefit for early sweet corn production.  Maturity is increased by 5-10 days, yields are generally increased by 15%-20%, and the first generation corn borer can be controlled if the covers are left on until after the peak of the first generation corn borer flight.  They can also be used to pre-warm the soil before planting.  They can be removed to allow planting and then replaced.  Weight cover edges with soil or sand bags to prevent damage by gusty winds, but leave adequate slack for plant growth to the tassel stage.

Transplanting Sweet Corn

Transplanting sweet corn offers some advantages to growers over direct seeding, including better stands, earlier harvest, and less dependence on pre-emergent herbicides.  However, transplanting is more labor intensive, costly and requires attention to detail in order to be successful.

Corn can be seeded by hand, or a simple, inexpensive drop seeder can be built to fit the size of tray to be used.  98-128 cell trays work best (a 128 cell tray requires 82 trays per acre).  The smaller plug trays require less media, but are more easily root-bound. Fill trays with a peat-based potting mix, and plant one or two seeds per cell.  Place trays on tables or benches to prevent plants from rooting in the ground.  Greenhouse temperatures should be set for 65-degree days and 60-degree night temperatures. Transplants should be ready in about 14-18 days, and should be hardened off before planting in the field, by placing the trays outdoors and limiting water for a few days.  Fertilizer should be banded prior to planting, or applied as a liquid at planting.  The plants should have good, cohesive roots that come out of the tray with relative ease. They may be planted by hand or machine.  Plants can be spaced 14-16 inches apart within rows, with about 3 feet between rows.  Floating row covers should be placed over the corn for the first two to three weeks after planting.  These can be pulled back to allow cultivation.  Transplanting and row covers should bring corn to maturity about two weeks earlier than direct seeding.  Not all varieties perform well in this system.  Test your favorite early-mid maturity varieties in small trials before committing large amounts of trays and greenhouse space to them. 

Harvesting and Storage

The sweetness and tenderness of sweet corn will deteriorate rapidly after harvest. Sweet corn should be cooled immediately after harvest and kept at 32º F to retain optimum freshness. The crop is best harvested early in the morning when there is less field heat. Harvesting at the proper stage (milk stage) is critical in maintaining quality. During the summer, sweet corn will be at the proper stage only 1-2 days. It will approach maturity 16-22 days after silking and should be picked daily. As the kernel passes the prime harvest time, sugars convert to starch and the pericarp becomes tough. Supersweet varieties retain their sweetness longer than su and se varieties; extra tender varieties maintain eating quality even longer.

Disease Control

NOTE: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 25 and Fungicides and Bactericides Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Leaf Spots (Helminthosporium, Cochiliobolus, Cercospora)

Plant resistant varieties. Improve air circulation by plant spacing and site selection. Plow under crop debris promptly after harvest to speed decomposition. Fungicide rotation is critical for prevention of resistance development- do not make back-to-back applications of products with active ingredients from the same group.

azoxystrobin (Quadris F AKA Abound F): 6.0 to 15.5 fl oz/A; PHI 7d, REI 4h, Group 11. May be extremely phytotoxic to certain apple varieties. See label for restrictions. 

azoxystrobin & propiconazole (Quilt): 7.0 to 14.0 fl oz/A; PHI 14d (sweet), PHI 30d (popcorn), REI 12h, Groups 11 & 3. 

chlorothalonil (Bravo Weather Stik AKA Bravo 720): 0.75 to 2.0 pt/A; PHI 14d, REI 12h, Group M05. Do not apply to sweet corn to be processed. Not labeled for popcorn.

fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d (sweet), PHI 21d (popcorn), REI 12h, Groups 7 & 11.

mancozeb (Dithane F45): 1.2 qt/A; PHI 7d, REI 24h, Group M03

propiconazole (Tilt): 2.0 to 4.0 fl oz/A; PHI 14d (sweet), PHI 30d (popcorn), REI 24h, Group 3.

pyraclostrobin (Headline): 6.0 to 12.0 fl oz/A; PHI 7d, REI 12h, Group 11.

pyraclostrobin plus metaconazole (Headline AMP AKA BAS 556 SC): 8.0 to 14.4 fl oz/A; PHI 7-20d (see label), REI 12h, Groups 11 & 3.

trifloxystrobin plus propiconazole (Stratego): 10.0 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.

Northern Corn Leaf Blight (Exserohilum (Helminthosporium) turcicum)

Northern corn leaf blight is an emerging problem on farms up and down the Connecticut River Valley. Northern corn leaf blight can develop very rapidly resulting in a complete blighting of leaves. E. turcicum overwinters in and on leaf debris and conidia can be spread long distances by wind. Under the right conditions (prolonged leaf wetness, extended rainy and humid weather, moderate temperatures), conidia are produced abundantly and disease spread is rapid. Reduce primary inoculum by crop rotation and tilling under of crop residue. Evidence suggests more severe disease in reduced-till systems; 1-year rotations are suggested for conventional practices and 2-year rotations for reduced-till. Resistant hybrids of all maturity groups are available. Lesions may vary in morphology when certain genes for resistance to this disease are present. The presence of these genes results in long, yellow, linear streaks that resemble the symptoms of Stewart's Wilt. Growing susceptible varieties will cause the resistance of nearby resistant varieties to break down. Fungicide rotation is critical for prevention of resistance development- do not make back-to-back applications of products with active ingredients from the same group.

azoxystrobin (Quadris F AKA Abound F): 6.0 to 15.5 fl oz/A; PHI 7d, REI 4h, Group 11. May be extremely phytotoxic to certain apple varieties. See label for restrictions.

azoxystrobin plus propiconazole (Quilt):  7.0 to 14 .0fl oz/A; PHI 14d (sweet), PHI 30d popcorn), REI 12h, Groups 11 & 3.

chlorothalonil (Bravo Weather Stik AKA Bravo 720): 0.75 to 2 pt/A; PHI 14d, REI 12h, Group M05. Do not apply to sweet corn to be processed. Not labeled for popcorn.

fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d (sweet), 21d (popcorn), REI 12h, Groups 7 & 11.

mancozeb (Dithane F45): 1.2 qt/A; PHI 7d, REI 24h, Group M03. 

propiconazole (Tilt): 2.0 to 4.0 fl oz/A; PHI 14d (sweet) PHI 30d (popcorn), REI 24h, Group 3.

pyraclostrobin (Headline): 6.0 to 12.0 fl oz/A; PHI 7d, REI 12h, Group 11.

pyraclostrobin plus metaconazole (Headline AMP AKA BAS 556 SC): 8.0 to 14.4 fl oz/A; PHI 7-20d (see label), REI 12h, Groups 11 & 3.

trifloxystrobin plus propiconazole (Stratego): 10.0 fl oz/A; PHI 14d (sweet), 30d (popcorn), REI 12h, Groups 11 &3.

Rust (Puccinia species)

The common rust fungus that occurs on sweet corn does not overwinter in the Northeastern United States; each year it is blown up from the south. Rust can cause significant reduction in ear weight and yield on susceptible varieties. Corn is more susceptible to infection prior to tasseling so later maturing plantings may have higher losses. Fungicides will control this disease but should be applied before tasseling. Apply fungicides when 80% of the plants show 1 or more pustules per leaf. Resistant varieties are available. Fungicide rotation is critical for prevention of resistance development- do not make back-to-back applications of products with active ingredients from the same group.

azoxystrobin plus propiconazole (Quilt): 10.5 to 14 fl oz/A; PHI 14d (sweet), PHI 30d (popcorn), REI 12h, Groups 11 & 3.

benzovindiflupyr (Trivapro A): 4.0 to 10.5 fl oz/A (see label); PHI 7d, REI 12h, Group 7.

chlorothalonil (Bravo Weather Stik AKA Bravo 720): 0.75 to 2 pt/A; PHI 14d, REI 12h, Group M5. Do not apply to sweet corn to be processed. Not labeled for popcorn.

fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d (sweet), 21d (popcorn), REI 12h, Groups 7 & 11.

mancozeb (Dithane F45 ): 1.2 qt/A; PHI 7d, REI 24h, Group M03.

propiconazole (Tilt): 4.0 fl oz/A; PHI 14d (sweet), PHI 30d (popcorn), REI 24h, Group 3. 

pyraclostrobin (Headline): 6.0 to 12.0 fl oz/A; PHI 7d, REI 12h, Group 11.

pyraclostrobin plus metaconazole (Headline AMP): 8.0 to 14.4 fl oz/A; PHI 7-20d (see label), REI 12h, Groups 11 & 3.

trifloxystrobin plus propiconazole (Stratego): 10.0 fl oz/A; PHI 14d, REI 12h, Groups 11 &3.

Seed Decay

Buy treated seed. Do not use treated seed for food, feed or oil purposes.

Common Smut (Ustilago maydis)

Smut occurs sporadically from one season to another but usually less than 2% of the plants are affected. The disease is favored by dry conditions when temperatures are between 80° F and 90° F and nitrogen fertility is high. Injury due to cultivation, hail or wind-blown sand can increase the incidence of disease when environmental conditions are favorable. Fungicides will not provide effective control of common smut.

Stalk Rots (Gibberella, Stenocarpella, Macrophomina, Colletotrichum, Fusarium)

Fungal stalk rots continue to be serious diseases of corn. Their occurrence and severity vary from year to year. Stalk rots cause losses by causing premature plant death, difficulties with mechanical harvesting,  and ear rot due to contact of ears with the soil. Factors that influence stalk rot include the susceptibility of the hybrids, weather conditions, the presence of foliar diseases, plant densities, insect damage, moisture availability, soil fertility, and tillage practices. Soil fertility, tillage, and plant density can be adjusted to provide control. Stalk rot is more severe and more common where soil fertility is high. Nitrogen (N) levels can both increase and decease stalk rot; an excess of N in relation to potassium (K) increases stalk rot. A balanced and continuous supply of N reduces the occurrence of stalk rot. Adequate K reduces stalk rot severity by strengthening cell walls. In general, corn debris left on the surface of the soil harbors many foliar diseases that increase stalk rot by reducing photosynthesis. As the population of plants increases, the incidence and severity of stalk rot also increase, especially in susceptible hybrids. Control is most successfully achieved through the use of resistant hybrids. Cultural practices such as balanced fertility, proper plant spacing, and reduction of other plant stresses, such as insect damage, can also reduce stalk rot.

Stewart's Wilt (Pantoae (Erwinia) stewartii )

This bacterial disease is spread by the corn flea beetle and is particularly damaging when susceptible varieties are planted following mild winters. P. stewartii overwinters in the alimentary tract of adult corn flea beetles, not in the soil or in plant debris. Severity of Stewart's Wilt depends on three factors: the winter temperatures prior to planting, the amount of disease the previous season, and cultivar susceptibility. If cold winter temperatures occur, fewer flea beetles survive to transmit the disease. The amount of disease in the previous season determines the percentage of emerging beetles carrying the bacterium. Hybrids with greater levels of resistance can tolerate more infection with less yield loss. Resistance restricts the movement of the bacteria in the plant. Grow varieties that are resistant to the disease.  Use insecticides to control flea beetles, particularly on susceptible varieties in the seedling stage. This is not as effective as resistant varieties, but reduces losses where susceptible hybrids must be planted. Scout frequently for flea beetles as rapid growth of leaf tissue makes untreated surfaces available.

 Maize Dwarf Mosaic Virus (MDMV)

There are several strains of MDMV which are spread by more than 20 species of aphids. The virus can be seedborne in maize and probably in some annual grasses. The virus is nonpersistent but is retained by the aphid for up to 18 hours. This allows time for the vector to be transported from southern states where MDMV is more prevalent and many weed hosts occur. Johnson grass is an important perennial weed host for MDMV occurring in southern New England and it should be eradicated. Plant resistant or tolerant corn varieties. Golden Gleam, Sundance, Spring Gold, Seneca Star, Early Fortune, Sugar Loaf, Dandy and Capitan have some tolerance. Enforcer, Biguard, Silver Red and Seneca 258 are resistant. MDMV is more likely to be a problem for later plantings. Plant late plantings away from peach trees, overwintering host of the green peach aphid.

Insect Control

NOTES:  For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 26 and Insecticides Alphabetical Listing by Trade Name for more information on these insecticides.

The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.

The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

All tolerances for chlorpyrifos in food crops were revoked in 2022, therefore products containing chlorpyrifos (e.g. Lorsban) cannot be applied to any food crop and growers CAN NOT use up existing stock.

Caution: Insecticides should not be applied when bees are active in the field.  Avoid products with high bee toxicity during pollen shed. If application of an insecticide is necessary while the crop is blooming, select products with low bee toxicity or with short residual period; apply in the evening after the bees have left the field. See Protecting Honeybees and Native Pollinators in the Insect Management section for more suggestions on how to avoid harmful effects on pollinators.

Sprayer Type and Configuration

In sweet corn, the best coverage is achieved with a boom-type sprayer with drop nozzles. The nozzles should be arranged so that one nozzle is over the row and a double-drop system is used between rows, with the lower nozzle is directed up toward the ear and upper nozzle directed down, to bracket the ear zone.  For whorl and pretassel stages, one nozzle over the row or with a single drop nozzle is adequate. Use hollow-cone nozzles at 75 to 100 psi to achieve good penetration, droplet size and coverage.  Mist blowers do not provide as effective coverage of the ear zone and may result in poorer coverage in the center of the block because each row of corn acts as a filter. However, on hilly land or for other reasons a mist blower may be the most feasible sprayer option. If a mist blower is used, plant fewer rows per block for later corn when insect pressure is typically higher. Direct some spray over the canopy, so it can settle into the corn from above, as well as through the corn rows.  Spray only in very calm conditions. For all sprayers, assess sprayer coverage by clipping water-sensitive cards on ears at the edge and center of the block and on both sides of the plant, then spraying water at the pressure and speed normally used.

Armyworm, Fall (Spodoptora frugiperda) and Common (Pseudaletia unipunctata)

The fall armyworm (FAW) does not overwinter in New England. Infestations result from moths carried northward on storm fronts from mid-July into September. Flights are heavier near the coast, but occur inland as well. FAW flights are sporadic and unpredictable, and do not necessarily correspond with corn earworm flights, so monitoring with pheromone traps in whorl stage corn is very useful. Male adult moths are ¾" long and have mottled brown forewings with a slanting white bar across the wing, and plain light tan hindwings. Female moths lay clusters of eggs on the leaves of a variety of host plants, preferring whorl stage corn to older corn. Eggs hatch in 2 to 10 days, depending upon temperature. Caterpillars are smooth (unlike CEW) and dark green or brown with lengthwise stripes and dark spots. Full-grown larvae reach 1.5 inch. The head capsule is dark with a distinctive light-colored marking in the form of an upside-down Y.

Feeding damage from caterpillars occurs first in whorl stage corn, deep within the whorl, on leaves and in the newly forming green tassel. In whorl stage corn, caterpillars produce ragged feeding damage to leaves and masses of sawdust-like excrement. As corn matures, larvae burrow into the side of corn ears, leaving behind frass and a large hole, and into the tip, making a mess of the kernels and rendering the ear unmarketable. When full grown, larvae drop to the ground and pupate in the soil. The most effective way to prevent ear damage is to apply controls during whorl and tassel stage. If flights remain high throughout ear development, silk sprays may be needed.

Monitor fall armyworm moth flight with a bucket trap (e.g., Universal Moth Trap or Multipher traps) with a lure clipped under the lid (Scentry 4-component lure is recommended) and a vapor strip placed inside the trap. Hang the trap on a stake at plant height in whorl stage corn. Identify and count FAW moths at least weekly. Flag the location well and move the trap to younger corn at tasseling. Replace the lure every 2 to 4 weeks, and the vapor strip every 6 to 8 weeks.

Scout whorl and emerging tassel stage corn by checking 100 plants in groups of 10 or 20 in a V or X pattern across the field. Avoid checking only field edges and select plants at random, not only where you can see damage. A plant is ‘infested’ if at least one caterpillar is found. If feeding damage is old and no larva is found, the caterpillar may have left the plant to pupate in the soil. If 15% or more of plants are infested with FAW, a control is needed.
In emerging tassels, combine counts for ECB and FAW. For example, if 10% of plants have FAW and 12% have ECB, the combined infestation is 22%, above the 15% threshold.

Common armyworm, also known as armyworm or true armyworm, migrates from southern areas anytime from March to September. Eggs are laid on grasses and grains in preference to corn and other crops. Larvae feed at night and are grayish green with a broad stripe on each side and a yellow-brown head. Damage is similar to fall armyworm and is often spotty and not sufficient to require treatment. Outbreaks are not common in New England but do occur occasionally, and can cause significant damage.

alpha-cypermethrin (Fastac* EC): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Bacillus thuringiensis aizawai (XenTariOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Use alone to control light populations or first and second instar larvae. Add a contact insecticide to control more mature larvae and higher populations. Must be ingested; apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt kurstaki products (Dipel).

Bacillus thuringiensis kurstaki (Dipel DFOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Use alone to control light populations or first and second instar larvae. Add a contact insecticide to control more mature larvae and higher populations. Must be ingested; apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt aizawai (XenTari).

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A. For first and second instar only.

Burkholderia spp. strain A396 (Venerate XCOG): 1 to 8 qt/A; PHI 0d, REI 4h, Bee: M. Group UN.

carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d ears, REI 24h or 21 days for workers detasseling corn, Bee: H, Group 1A. For fall armyworm. Hand harvesting is prohibited. Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies.

chlorantraniliprole (Coragen): 3.5 to 7.5 oz/APHI 1d, REI 4h, Bee: L, Group 28. For foliar applications.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M. Group UN.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Apply to early instar larvae prior to boring into ear or stalk.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. For fall armyworm, target first and second instar only. Direct the application to the ear zone to obtain thorough coverage of the corn silk.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. FAW only.

indoxacarb (Avaunt): 2.5 to 3.5 oz/A; PHI 3d, REI 12h for mechanically harvested and 14 days for hand harvested, Bee: H, Group 22. Whorl through tassel emergence (prior to silking) application only. For fall armyworm only.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Use high rate for large larvae.

methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. Some sweet corn varieties may be damaged by methomyl. More severe damage may occur with the Lannate* LV formulation than with the Lannate* SP (Soluble Powder) formulation.

methoxyfenozide (Intrepid): 4 to 16 fl. oz./A; PHI 3d, REI 4h, Bee: L, Group 18.

methoxyfenozide + spinetoram (Intrepid Edge): 4 to 12 fl. oz./A; PHI 3d, REI 4h, Bee: M, Group 5 & 18.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

spinetoram (Radiant SC): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Apply as directed spray into leaf whorls or as broadcast spray.

spinosad (Entrust SCOG): 1.5 to 6 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Apply as directed spray into leaf whorls or as broadcast spray.

zeta-cypermethrin (Mustang*): 3 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Brown Marmorated Stink Bug (Halyomorpha halys)

See stink bugs in the insect control section of Tomato, Outdoor for information on brown marmorated stink bug.       

acetamiprid (Assail): 2.3 oz./A; PHI 7d, REI 12 h, Bee: M, Group 4A. Suppression only.

bifenthrin (Brigade* 2EC): 6.4 oz/A; PHI 1d, REI 12 hr, Bee: H, Group 3A. Do not make aerial or ground applications to corn if heavy rainfall is imminent.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

methomyl (Lannate* LV): 1.5 pt/A; PHI 0d, REI 48h, Bee: H, Group 1A.

Corn Earworm (Helicoverpa zea)

Corn earworm (CEW) moths migrate annually into the Northeast, traveling north on storm fronts, and may arrive anytime from late June through September. Heaviest numbers are found in coastal areas and up the major river valleys. The severity of infestations varies from year to year and may change suddenly during the season. CEW feeds in a wide range of crops and among vegetables its favorite crops are corn and tomato (hence it is also known as ‘tomato fruitworm’). 

Adult moths are light tan with a distinctive dark spot on each forewing, and a dark band near the margin of the hind wing, and a wingspan of 1.2" to 1.5". Live moths have bright green eyes. Moths are active at night. Fresh silk is highly attractive for egg-laying.  When migratory flights arrive, females are ready to lay eggs. Single, globe-shaped eggs are laid directly on fresh silk and hatch in 2.5 to 6 days depending on temperature. Newly-hatched caterpillars crawl down the silk channel and feed on the kernels at the tip, leaving unsightly frass. In the tip, they are protected from insecticide sprays. Corn earworm larvae may be brown, tan, green, or pink, with light and dark longitudinal stripes and reach 1.5 to 2" when full grown. CEW can be distinguished from FAW and ECB by the plain, golden brown head capsule and small bumps and spines that give the body a rough texture.

Monitoring moth flight with pheromone traps is key to successful season-long control, because it enables farms to respond quickly to changes in flight and to avoid unnecessary sprays. Reports of moth trap captures at selected locations are provided in most New England states. The most accurate and timely flight information will be obtained by monitoring your own fields. Heliothis net traps baited with Hercon Heliothis zea pheromone lures are commercially available and widely used in the region. Place traps in blocks with fresh silk and count moths twice weekly to monitor average nightly catch. Replace lures every 2 weeks and move traps to a block with fresh silk as soon as silk dries.

Sprays or other control measures must be timed to prevent larvae from entering the ear. Control depends upon maintaining insecticide coverage on the silks when eggs are being laid and hatching. Directed sprays to the ear zone provide the best control. Repeat applications to silk every 3 to 6 days depending on trap captures according to the chart below. If maximum daily temperature is below 85º F for 2 to 3 days, spray intervals may be extended by 1 day. Continue treatments until 5 to 7 days before final harvest or until silk is completely dry and brown. Use selective materials to conserve natural enemies of aphids and other pests.

Spray Intervals for Corn Earworm

Based on moth captures in Heliothis net traps

Moths/Night Moths/Week Spray Interval
0 - 0.2 0 - 1.4 no spray
0.2 -0.5 1.4 - 3.5 6 days
0.5 - 1 3.5 – 7 5 days
1 - 13 7 – 91 4 days
Over 13 Over 91 3 days

Bt hybrids that express the insect toxin found in Bacillus thuringiensis (Bt) in leaves, husks and kernels offer protection against CEW and may not require additional insecticide applications for control of this pest.

alpha-cypermethrin (Fastac* EC): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Bacillus thuringiensis aizawai (XenTariOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Use alone to control light populations and add a contact insecticide to control moderate to heavy populations. Maintain frequent spray intervals.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

Burkholderia spp. strain A396 (Venerate XCOG): 1 to 8 qt/A; PHI 0d, REI 4h, Bee: M. Group un.

carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d ears, REI 24h or 21 days for workers detasseling corn, Bee: H, Group 1A. Hand harvesting is prohibited. Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies.

chlorantraniliprole (Coragen): 3.5 to 7.5 oz/APHI 1d, REI 4h, Bee: L, Group 28. For foliar applications.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M. Group UN.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Apply to early instar larvae prior to boring into ear or stalk.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group A. Some corn varieties may be damaged by methomyl. More severe damage may occur with the Lannate* LV formulation than with the Lannate* SP (Soluble Powder) formulation. May not provide effective control under high corn earworm pressure.

methoxyfenozide (Intrepid): 4 to 16 fl. oz./A; PHI 3d, REI 4h, Bee: L, Group 18.

methoxyfenozide + spinetoram (Intrepid Edge): 8 to 12 fl. oz./A; PHI 3d, REI 4h, Bee: M, Group 5 & 18.

nuclear polyhedrosis virus of Helicoverpa zea (GemstarOG): 4-10 fl. oz./A; PHI 0d, REI 4h, Bee:L, Group UN. Do not tank mix with Bt products. Frequent application at low rates is usually more effective than infrequent application at high rates.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

soybean oil (Golden Pest Spray OilOG): 0.5 ml applied by hand directly to silk within 6 to 7 days after 50% of the ears are silking; REI 4h, Bee: L, Group 25. Apply at least 5 days after silk initiation to avoid tip injury, and before 7 days after silk initiation to gain optimum control. Mix with Bacillus thuringiensis, spinosad or neem for improved control. One application per field. Commercial oil applicators (i.e., Zea-later) are available.

spinetoram (Radiant SC): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Apply as broadcast or directed spray into ear zone.

spinosad (Entrust SCOG): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Apply as directed spray to ear zone or as broadcast spray; ensure thorough wetting of silks. Effective for low to moderate CEW pressure; may be less effective when CEW pressure is high (13 or more moths/night in pheromone trap) or when a 3-day spray schedule is warranted. A 1 to 2-day re-treatment schedule may be necessary at silking.

zeta-cypermethrin (Mustang*): 3 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Corn Leaf Aphid (Rhopalosiphum maidis)

The corn leaf aphid (CLA) is blue-green or black, with black legs. These aphids overwinter as eggs or females on grass weeds and grains, including barley and wheat. When these cereals mature, winged aphids develop and migrate to corn and wild grasses.  Both winged and wingless female aphids occur together.  Females produce live young (nymphs) which mature in as little as 6 days, resulting in many generations per year. In corn, CLA first colonize whorl leaves and the immature tassel. Populations may become numerous enough to interfere with pollen shed and to stunt plants, and to infest layers of the husk with aphids. Maize dwarf mosaic virus may be spread by the corn leaf aphid, though the most important vector for this disease is the green peach aphid. In addition, aphids excrete a sugary liquid called ‘honeydew’ which coats leaves and husks and encourage growth of sooty mold fungus. The presence of aphids and honeydew on corn husks reduces their marketability. Varieties with purple or green tassels seem to be less susceptible to aphid build-up than those with yellow tassels. Ample rainfall or irrigation during the silk stage can reduce or eliminate aphid damage. Natural enemies reduce aphid numbers, but may not provide adequate control, especially in dry seasons. Whenever possible, conserve predators and parasites by using selective insecticides to control caterpillars. Sweet corn plantings that are seeded before 10 June are generally not bothered by corn leaf aphids. Monitor for aphids while scouting whorl or pre-tassel stage corn for ECB or FAW in July and August. Pre-tassel stage sprays may be needed when 50% of the plants are infested, or if 25% have heavy infestations. Sprays applied before 50% of the tassels emerge are more effective than later sprays.

alpha-cypermethrin (Fastac EC*): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

acetamiprid (Assail): 0.9 to 1.2 oz./A; PHI 1d, REI 12 h, Bee: M, Group 4A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M. Group UN.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Suppression only.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

flupyradifurone (Sivanto): 7 to 14 fl oz/A; PHI 7d, REI 4h, Bee: M, Group 4D.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Suppression only.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Suppression only.

methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d for ears, PHI 3d if used for forage, REI 48h, Bee: H, Group 1A. See ECB section for phytotoxicity warning.

petroleum oil (Suffoil XOG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L.

thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4. Systemic seed treatment. Use standard slurry seed treatment equipment to ensure uniform coverage of kernels. For early season protection from corn leaf aphid.

Cutworms, including Black Cutworm (Agrotis ipsilon)

Black cutworm is the most common of the many cutworm species that damage corn in New England. Adults are night-flying tan and black moths, while the caterpillars are dark-grey to black and up to 2" in length. Moths from the South arrive between March and June. Eggs are laid mostly on grasses and winter annual weeds, usually near areas of the field prone to flooding. Certain fields tend to have a history of repeated cutworm damage. The larvae feed after dark while hiding under the soil surface during the day. There are 2 to 3 generations per year but usually only the first generation, which produces larvae in May and June, damages corn. Small larvae feed on leaves and occasionally larger larvae cut seedlings off near the soil line. Adults can be monitored with a yellow and white Unitrap from March through May. A catch of over 40 moths before June indicates that frequent spring and early summer scouting is prudent. Scout problem fields weekly, checking at least 100 plants for leaf feeding and cut stems, especially near field margins. Spot spray heavily hit areas or edges of the field if 5% of the plants have been cut down. For best results, make application between midnight and dawn while cutworms are feeding aboveground. Foliar-applied rescue treatments are recommended over preventative soil-applied insecticides. Ground beetles, parasitic flies and wasps and other general predators help reduce populations. When corn follows sod/hay in rotation, fall-plowing may lower cutworm populations by reducing spring egg-laying sites. Weedy and reduced-till fields tend to suffer the most damage.

alpha-cypermethrin (Fastac* EC): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

beta-cyfluthrin + tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A and 1B.

bifenthrin (Capture* LFR): 3.4 to 13.6 oz/A for at-plant applications; 4 to 5.3 oz/A for pre-plant incorporation applications; 3.4 oz/A for pre-emergence applications; REI 12h, Bee: H, Group 3A. Apply as T-band over open furrow or over the row on soil surface, in-furrow with the seed, or incorporated pre-planting to seed planting depth.

 

bifenthrin + Bacillus amyloliquefaciens strain D747 (Ethos XB): 8.5 to 17.0 fl oz/A, PHI 1d, REI 12h, Bee: H, Group 3A and BM 02 fungicide. Apply as a 5 to 7 inch band (T-band) over an open furrow, or in-furrow with the seed mixing. Can be mixed directly with liquid fertilizer. Biofungicide suppresses pathogens responsible for damping off. 

carbaryl (10% Sevin Granules): 10 lb/A; PHI 2d, REI 12h or 21 days for workers detasseling corn, Bee: H, Group 1A. Ground broadcast equipment applications only. Hand harvesting prohibited.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee:H, Groups 28 & 3A.

deltamethrin (Delta Gold*): 1 to 1.5 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Apply to early instar larvae prior to boring into ear or stalk.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

ethoprop (Mocap* 15%G): 20 lb/A; REI 48h, Bee: H, Group 1B. Apply 3 days before planting toat-planting time. Broadcast and incorporate immediately into top 2" of soil.

gamma-cyhalothrin (Declare*): 0.041 oz/1000 row ft for at-plant soil application, 1.02 to 1.54 oz/A foliar; PHI 1d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 0.33 fl oz/1,000 ft. as T-band or furrow application at planting, 1.28 to 1.92 oz/A foliar; PHI 1d, REI 24h, Bee: H, Group 3A. 

methomyl (Lannate* SP): 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. Some sweet corn varieties may be damaged by methomyl. More severe damage may occur with the Lannate* LV formulation than with the Lannate* SP (Soluble Powder) formulation.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

spinosad (SeduceOG): 20 to 44 lb/A or 0.5 to1 lb/1000 sq ft.; PHI 1d, REI 4 h, Bee: M, Group 5. Spread bait on soil around plants; reapply after heavy rain or at least every 2 to 4 weeks but not more than 3 times per 30 days.

tefluthrin (Force* CS): 0.46 to 0.57 oz/1000 row feet; REI 48h, Bee: H, Group 3A. For t-banded or in-furrow applications.

thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. Use standard slurry seed treatment equipment to ensure uniform coverage of kernels. For early season protection from black cutworm.

zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

European Corn Borer (Ostrinia nubilalis)

European corn borer (ECB) is a resident pest that has 2 generations per year in southern and central New England and 1 generation in northern New England. Sweet corn is one of over 200 crop and weed host plants of this pest; other vegetable crops affected include bean, pepper and potato. Larvae overwinter in stalks of corn and other host plants and pupate in the spring. Adult moths emerge in late May or early June and mate in weedy or grassy areas. Growing degree days (GDD) with a base temperature of 50°F may be used to predict the beginning of moth flight (374 GDD), first eggs (450 GDD), and peak flight (631 GDD). The moths are about ¾" long, light brown in color with lighter bands on the wings. Three to 7 days after emergence, depending on temperature, females begin to lay flat, white egg masses on the underside of leaves in early corn. Eggs hatch in about 5 to 7 days (100 degree days). ECB larvae are light-colored, with a pattern of small dark spots on each segment. The head capsule is flattened and black or dark brown. Newly hatched larvae are 1/8" long and full-grown larvae are 3/4" to 1" long. Larvae feed in the whorl, leaving pinhole damage, and in the succulent emerging tassel creating brown frass in the florets. As the corn matures, these larvae move downward, bore into the stalk and tunnel into ears through the side or tip. Pupae form inside larval tunnels in the stalk. A second flight begins in mid-July to mid-August, depending on location and the seasonal growing degree day accumulation (beginning of second flight, 1400 GDD; first eggs 1450 GDD; egg hatch 1550 GDD). When moths are active during silking, eggs are laid on leaves near the ear and larvae move directly into the ear by tunneling through the husk or down the silk channel.

Since the ECB overwinters as a mature larva in corn stalks and stubble, plowing under corn refuse in the fall or early spring will help control this pest. Fields that have been in sweet corn or field corn for a long time tend to have higher pressure from ECB. Weedy fields also have higher pressure.  Natural enemies include the twelve-spotted ladybeetle which preys on eggs and small larvae. Releases of Trichogramma ostriniae, a tiny parasitic wasp which attacks ECB eggs, can reduce the need for insecticide applications. See Table 22, Biological Controls for Insect Pests for more information.

ECB flight can be monitored with 2 Scentry Heliothis net traps baited with either a New York E (II) or Iowa Z (I) lure, placed at least 50'  apart in weedy borders of corn fields with the bottom at weed height. Both types of lures are needed in New England because both E and Z strains are present. Check traps once or twice per week and replace lures every 2 weeks. Once flight is detected, corn with newly emerging tassels should be scouted weekly for the presence of ECB larvae by inspecting the tassels of 50 to 100 plants, in groups of 5 to 20 plants throughout the field. Treat if more than 15% of the plants have one or more larvae present. Timing sprays for tassel emergence reaches larvae in the whorl and the young tassel. A sprayer configuration with one nozzle directed into the tassel and a single drop nozzle to the upper parts of the plant gives the best control.  At high levels of infestation, 2 applications may be needed to provide control. Use of selective products to control ECB will conserve natural enemies of aphids and ECB.

Corn started under plastic or row cover often reaches silk stage during the first flight of ECB, such that the first eggs laid hatch during ear development. As a result, ears can be heavily infested by this pest even though scouting in early tassel did not show any feeding damage or larvae. If plants are in silk and moths are active, it is important to protect developing ears. This is also true for late season corn during the second ECB flight, especially when other caterpillar pests are absent.

Genetically modified Bt hybrids that express the insect toxin found in Bacillus thuringiensis (Bt) generally provide adequate defense against European corn borer and may not require additional insecticide applications, but scouting is still recommended to assess ECB and other pests.

alpha-cypermethrin (Fastac* EC): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Bacillus thuringiensis aizawai (XenTariOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. See the general recommendations for B.t. kurstaki below. For resistance management, may be rotated with Bt kurstaki products.

Bacillus thuringiensis kurstaki (Dipel DFOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested; apply when larvae are actively feeding. Ensure good coverage and use a spreader sticker. Use a shorter spray interval (4 to 5 days) and high rates under high borer pressure. For resistance management, may be rotated with Bt aizawai (XenTari).

Burkholderia spp. strain A396 (Venerate XCOG): 1 to 8 qt/A; PHI 0d, REI 4h, Bee: M. Group un.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A. Applications must be made prior to larva boring into the plant.

carbaryl (Sevin XLR Plus): 1.5 to 2 qt/A; PHI 2d ears, REI 24h or 21 days for workers detasseling corn, Bee: H, Group 1A. Hand harvesting is prohibited. Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies.

chlorantraniliprole (Coragen): 3.5 to 7.5 oz/APHI 1d, REI 4h, Bee: L, Group 28. For foliar applications.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M. Group UN.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Apply to early instar larvae prior to boring into ear or stalk.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

indoxacarb (Avaunt): 2.5 to 3.5 oz/A; PHI 3d, REI 12h for mechanically harvested and 14 days for hand harvested, Bee: H, Group 22. Whorl through tassel emergence (prior to silking) application only.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Use higher rates for large larvae.

methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. Treat a small area of the field to determine cultivar sensitivity before spraying entire field. Phytotoxicity may occur on some varieties. More severe damage may occur with the Lannate* LV formulation than with the Lannate* SP (Soluble Powder) formulation.

methoxyfenozide (Intrepid 2F): 4 to 16 oz/A; PHI 3d, REI 4h, Bee: L, Group 18. Direct application at the whorl for early season infestations; broadcast over row for mid- to late-season infestations.

methoxyfenozide + spinetoram (Intrepid Edge): 4 to 12 fl. oz./A; PHI 3d, REI 4h, Bee: M, Group 5 & 18.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

spinetoram (Radiant SC): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Apply as directed spray into leaf whorls or as broadcast spray.

spinosad (Entrust SCOG): 1.5 to 6 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Apply as directed spray into leaf whorls or as broadcast spray. Time applications to coincide with peak egg hatch of each generation. Frequent treatments may be necessary when the crop is growing rapidly, during silking or under heavy pest pressure.

zeta-cypermethrin (Mustang*): 3 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Flea Beetle, Corn (Chaetocnema pulicaria)

Corn flea beetles are black, tinged with bronze or bluish green, and overwinter in plant residue around the fields. They move to corn seedlings in early spring, where they feed and lay eggs in soil. Direct feeding damage is not significant, but economic damage can be caused by Stewart’s bacterial wilt, which is vectored by the beetles.  Cold winters reduce the risk of this disease, while mild winters improve beetle survival and hence transmission of wilt. A Winter Temperature Index uses the sum of the average monthly temperatures of December, January and February (in ºF) to forecast the Stewart’s wilt severity for the season: wilt is predicted to be absent if the Index is <90º F, intermediate if 90º F to 100º F, and destructive if >100º F.   The disease may appear on the earliest plantings and grow worse on succession plantings of susceptible varieties. Use resistant or tolerant varieties where possible, especially on early plantings (see Sweet Corn Varieties Section). Spunbonded row covers protect plants against this pest. Scout on sunny, calm days when beetles are active. Start applications when plants are in the spike stage if beetles are present and causing damage, especially on susceptible varieties. Apply additional treatments as needed.

alpha-cypermethrin (Fastac* EC): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

acetamiprid (Assail): 1.7 to 2.3 oz./A; PHI 7d, REI 12 h, Bee: M, Group 4A.

beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d ears, REI 24h or 21 days for workers detasseling corn, Bee: H, Group 1A. Hand harvesting is prohibited. Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee:H, Groups 28 & 3A.

deltamethrin (Delta Gold*): 1 to 1.5 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. See ECB section for phytotoxicity warning.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

phorate (Thimet* 20-G): 4.5 to 6 oz/1,000 row feet; PHI 30d, REI 48h, Bee: H, Group 1B. Apply in a 7" band over the row at planting and lightly incorporate. DO NOT use in-furrow.

terbufos (Counter* 20G): 4.5 to 6 oz/1,000 row feet for any row spacing; REI 48h, Bee: M, Group 1B. Place granules in seed furrow behind planter shoe or in a 4-5" band over the row, and lightly incorporate.

thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. Use standard slurry seed treatment equipment to ensure uniform coverage of kernels. For early season protection from corn flea beetles.

zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

Japanese Beetle (Popillia japonica)

These beetles feed on corn silk, but are usually controlled by sprays directed at controlling ECB and corn earworm.

alpha-cypermethrin (Fastac* EC): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

acetamiprid (Assail): 2.3 oz./A; PHI 7d, REI 12 h, Bee: M, Group 4A.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A. Adults only.

carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d ears, REI 24h or 21 days for workers detasseling corn, Bee: H, Group 1A. Hand harvesting is prohibited. Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Adults only.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Adults only.

lamba-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Adults only.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A. Adults only.

Sap Beetles, Fourspotted (Glischrochilus quadrisignatus) and Dusky (Carpophilus lugubris) Sap Beetle

Sap beetle problems are more likely to occur on farms producing a variety of fruit and vegetable crops. Adult beetles are 3/16" long and are black (Dusky sap beetle), or black with orange spots (Fourspotted sap beetle, also known as ‘picnic beetle’). They survive the winter as pupae or adult beetles under soil or plant debris in fields, or under leaf litter along hedgerows and field margins. Eggs may be deposited in rotting fruit or discarded vegetable debris (cull piles), in wounds created by corn borer or birds, and on silk or in kernels at the tip of the ear.  Eggs are milky white and resemble tiny grains of rice, about 1/16" long. The larva is a white or light yellow grub that resembles a tiny, thin caterpillar or maggot. Larvae hollow out developing kernels, and damage may be found in the tip and scattered through the upper half of the ear.  Full grown larvae drop to the ground to pupate in the soil. Marketability of ears declines when damage, larvae or adults are present on or in kernels. Adults feed on pollen, sap, silk and injured or rotting fruit.  Males have an aggregation pheromone that attracts other beetles, both male and female. Adults move to corn at full tassel to feed on pollen, and build up as corn matures and silk turns brown. There are 2 to 4 generations per year with peak infestations in July (larvae) and late July and August (adults).

Cultural controls are essential to managing sap beetles. Ears with exposed tips, especially super sweet and Bt varieties, are more susceptible to infestation.  Research has shown that both the length and tightness of the tip cover is important to reduce infestations. Some varieties with long, tight tip cover include:  Accord, Argent, Avalon, Awesome, Bon Jour, Cuppa-Joe, Easy Money, Fantasia, Ka-Ching, Precious Gem, Prime Plus, Profit, Providence and Renaissance. To prevent or reduce damage, select varieties that have good tip cover, use clean cultivation, and control birds and ear-infesting caterpillars.  Eliminate or bury deeply any cull piles or other areas with decaying vegetables or fruit, included infested ears. Do not leave infested blocks standing; mow aggressively to chop ears as soon as the block is finished. Deep plowing may be necessary after harvest if infestations are high, to bury ears at least 4" deep.

Scout blocks at full tassel and early silk to determine if beetles are present. Unfortunately, there are no specific thresholds based on scouting. Insecticides may be warranted in fields with a previous history of 10% ear damage.  Research in Maryland showed that ear infestation begins just after silk emerges and that 1 or 2 applications made 3 and 6 to 7 days after silking begins is more effective than later or more applications. Insecticides will reduce the number of damaged kernels and ears but will not completely control heavy infestations.  Sap beetle adults and larvae are not susceptible to the Bt toxin that is present in Bt corn. Efficacy trials have shown that carbaryl (Sevin), lambda-cyhalothrin (Warrior II), bifenthrin (Bifenture), and methomyl (Lannate) are more effective than most other insecticides.  However, carbaryl cannot be used during the early silk period while corn is shedding pollen and does not allow for hand harvesting after use.

alpha-cypermethrin (Fastac* EC): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

acetamiprid (Assail): 1.7 to 2.3 oz./A; PHI 1d, REI 12 h, Bee: M, Group 4A.

carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d, REI 12h, Group 1A. 1 to 2 qt/A; PHI 2d ears, REI 24h or 21 days for workers detasseling corn, Bee: H, Group 1A. Hand harvesting is prohibited. Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies. Sap beetles only.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee:H, Groups 28 & 3A.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Adult sap beetle only. 

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Adult sap beetle only.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Adult sap beetle only.

malathion (Malathion 57 EC): 1.5 pt/A; PHI 5d, REI 12h or 72h for workers detasseling corn, Bee: H, Group 1B. Begin treatment when 10% of ears show silk. Apply when nymphs are young. Injury may occur in the whorl and silk stages using this type of Malathion product.

methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d for ears, PHI 3d if used for forage, REI 48h, Bee: H, Group 1A. See ECB section for phytotoxicity warning.

zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A. Adult sap beetle only.

Seedcorn Maggot (Delia platura)

See seedcorn maggot in the insect control section of Beans for more information about biology and management.

beta-cyfluthrin + tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A and 1B.

bifenthrin (Capture* LFR): 3.4 to 6.8 oz/A for at-plant applications; 4 to 5.3 oz/A for pre-plant incorporation applications; PHI 2d, REI 12h, Bee: H, Group 3A. Apply as T-band over open furrow, in-furrow with the seed, or incorporated pre-planting to seed planting depth.

gamma-cyhalothrin (Declare*): 0.041 oz/1000 row ft for at-plant soil application; PHI 1d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 0.33 fl oz/1,000 ft as T-band or furrow application at planting; PHI 1d, REI 24h, Bee: H, Group 3A.  

phorate (Thimet* 20-G): 4.5 to 6 oz/1,000 row feet in a 7" band over the row at planting and lightly incorporate; PHI 30d, REI 48h, Bee: H, Group 1B. DO NOT use in-furrow.

tefluthrin (Force* CS): 0.46 to 0.57 oz/1000 row feet; REI 48h, Bee: H, Group 3A. For t-banded or in-furrow applications.

terbufos (Counter* 20G): 4.5 to 6 oz/1,000 row feet; REI 48h, Bee: M, Group 1B. Place granules in seed furrow behind planter shoe or in a 4-5" band over the row, and lightly incorporate.

thiamethoxam (Cruiser 5FS): 1.28 to 5.1 fl oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. Use standard slurry seed treatment equipment to ensure uniform coverage of kernels. For early-season protection from seedcorn maggot.

Stalk Borer (Papaipema nebris)

Stalk borer (also known as common stalk borer) is an occasional pest of corn and of other vegetable crops. It is the egg stage that overwinters, on grassy weeds where adult moths deposited them in the fall. Upon hatching in the spring, the caterpillars feed on grasses by boring into and along the stalk. When the caterpillars become too large to feed within the grass, they migrate to nearby thicker-stemmed wild and cultivated plants. In corn, infestations are heaviest in border rows and in fields with grassy weeds. Borers feed in the stalk or deep in the whorl, which may kill the growing tip. Larvae are brown to purplish brown with a broad white stripe on the back and each side. These stripes are interrupted by a distinctive, large brown spot around the whole body.  Pupation occurs in the soil in late summer, with adult emergence and activity from August to October. There is one generation per year. Reduced tillage fields, which may have higher levels of grassy and broad-leaf weeds, may result in increased levels of stalk borer. To reduce overwintering eggs, prevent or eliminate grassy weeds especially from August on. Destroy weeds and grasses at field margins to reduce invasions at field borders. Scout for injury soon after the corn emerges in the spring and treat infested corn as needed. Apply insecticides to outer rows at the first sign of damage by this pest. Treat small larvae before they bore into stalks.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A. Application must be made prior to larva boring into the plant.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Apply to early instar larvae prior to boring into ear or stalk.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

Wireworms and White Grub

See wireworms in the insect control section of Potato for more information. To avoid wireworm problems, corn should not be grown in rotation with sod or grass crops. Delay planting susceptible crops, such as corn or potatoes, on such land for at least two years after the sod has been broken. Summer fallow is recommended for at least one season.

Land that was in sod or pasture should be planted to legumes, such as alfalfa or clover, for a year or more before planting corn or other vegetables to reduce the number of white grubs in the soil.  Plow or harrow in mid-summer, after harvesting early corn, to reduce grub numbers.

beta-cyfluthrin + tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A and 1B. 

bifenthrin (Capture* LFR):  3.4 to 13.6 oz/A for at-plant applications; 4 to 5.3 oz/A for pre-plant incorporation applications; PHI 2d, REI 12h, Bee: H, Group 3A. Apply as T-band over open furrow, in-furrow with the seed, or incorporated pre-planting to seed planting depth.

ethoprop (Mocap* 15%G): 8 oz/1,000 row feet; REI 48h, Bee: H, Group 1B. Apply as 6" to 7" band over closed seed furrow, then incorporate immediately into top 0.5" of soil. Suppression only for white grubs. Extremely toxic to birds; do not leave granules on soil surface.

gamma-cyhalothrin (Declare*): 0.021 oz/1000 row ft for at-plat soil applications; PHI 1d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 0.33 fl oz/1,000 ft. as T-band or furrow application at planting; PHI 1d, REI 24h, Bee: H, Group 3A.

phorate (Thimet* 20-G): 4.5 to 6 oz/1,000 row feet; PHI 30d, REI 48h, Bee: H, Group 1B. Apply in a 7" band over the row at planting and lightly incorporate. DO NOT use in-furrow.

tefluthrin (Force* CS): 0.46 to 0.57 oz/1000 row feet; REI 48h, Bee: H, Group 3A. For T-banded or in-furrow applications. Use high rate for heavy infestations. For best control, place in seed furrow.

terbufos (Counter* 20G): 4.5 to 6 oz/1,000 row feet; REI 48h, Bee: M, Group 1B. Place granules in seed furrow behind planter shoe or in a 4-5" band over the row, and lightly incorporate.

thiamethoxam (Cruiser 5FS): 1.28 to 5.1 fl oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. Use standard slurry seed treatment equipment to ensure uniform coverage of kernels. For early-season protection from wireworms and white grub (including Japanese beetle larvae, European chafer larvae, true white grub, annual white grub, May/June beetle larvae).

Weed Control

NOTE:  For the herbicides listed below, one product trade name and formulation is provided for each active ingredient along with preharvest interval (PHI), restricted entry interval (REI), resistance management group number, and example of rates and special instructions. In many cases there are other products available with the same active ingredient. However, not all products with the same active ingredient are registered for use in a crop. Always check the product label to be sure that the crop is listed before using. 

Delayed Herbicide Applications

Growers using atrazine (Aatrex) and or mesotrione (Callisto) for broadleaf weed control and either metolachlor (Dual) or pyroxasulfone (Zidua) for grass control in corn should consider delayed applications in their earliest plantings. Reasons for delaying herbicide applications in the earliest sweet corn plantings include:

  1. Corn is most tolerant to both Dual and Zidua after emergence. Supersweet varieties and some "se" sweet corns are easily injured by these herbicides when the soil is below 60°F. Both Dual and Zidua as well as atrazine and Callisto can be applied at any time as long as the corn is less than 5" high. Bicep Lite II, a very commonly used prepack of atrazine and Dual, can also be used this way as can Lumax, a prepack of metolachlor, atrazine, and mesotrione.
  2. If the first few plantings of sweet corn are sprayed on the same day, the amount of cleaning and rinsing of the spray tank is reduced since it does not need to be cleaned between applications when the same herbicide is used.
  3. Delaying herbicide applications on the earliest plantings will also extend the activity of the herbicide later into the season. This is important in maintaining good weed control throughout the season to minimize weed seed production. Growers often rely on sweet corn rotations to reduce weed seed populations in the soil.

Growers should consider waiting until their first planting of sweet corn is 3" to 5" high to apply herbicide. At this time all fields of sweet corn planted to date can be treated. Each field sprayed will be at a different stage of growth. After that, each field should be sprayed soon after it is planted, since soils will be warmer and grasses are more likely to emerge soon after seeding the crop.

A possible problem with delayed applications involves the potential for poor control of grasses. Dual, Zidua, Bicep (atrazine + Dual), or Lumax (atrazine + Dual + Callisto) must be applied before grasses emerge. If grasses are not controlled in corn, yield reductions will likely occur. Also, as the soil warms up, grasses are likely to emerge soon after seeding.

Reduced Herbicide Rates for Corn Weed Management 

Be sure to follow the herbicide rates recommended in this guide. Only 1 lb active ingredient of atrazine is recommended for sweet corn in New England. This is well below the rate on the label and constitutes best management practices for groundwater protection. This rate could be reduced further, although the grower should be prepared to make a second application of atrazine if any weeds escape. Rates for Dual and Lasso should be selected based on soil type. Follow the label to determine the correct rate. Reducing the rate of Dual or Zidua is risky since it is very difficult to control grasses in sweet corn once they emerge.

Special Atrazine Precautions

The Environmental Protection Agency and Syngenta have revised the label uses of all atrazine products to reflect the potential for surface and groundwater contamination. Be sure to read and follow all directions and restrictions listed on the label. The preceding section on Reduced Herbicide Rates for Corn Weed Management reflects these concerns. All of the rates listed in this guide for atrazine are within the guidelines of the label. These include uses for single applications (applied before crop emergence or early postemergence) and sequential applications (applied both at planting and postemergence). Please read all labels carefully.

Stale Seedbed Applications

The following herbicides are nonselective and are used to control weeds which are present in a field prior to planting the sweet corn or before the sweet corn emerges (see Stale Seedbed Technique, page 107). If a grower is using "no-till" or "minimum tillage," these herbicides are also used to kill the cover crop that may be present in the field.

glyphosate (Roundup Power Max): REI 12h, Group 9. Apply to emerged annual or perennial weeds prior to crop emergence. Do not feed crop residue to livestock for 8 weeks following treatment. Consult the manufacturer's label for specific weeds and rates. May be tank mixed with atrazine, simazine or alachlor.

paraquat (Gramoxone SL 2.0*): restricted use. REI 12h, Group 22. Use 2 – 4 pts/A.  Apply in 20 to 60 gallons spray mix to emerged weeds. Field should be prepared several days ahead of treatment to allow maximum weed emergence. Use a nonionic surfactant at a rate of 16 to 32 oz per 100 gal spray mix. May be tank mixed with atrazine or simazine preemergence. Can also be applied as a preemergence. Check label for directions. May be fatal if swallowed or inhaled. Applicators must complete an EPA-approved paraquat training listed on the following website https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training...(link is external). The training must be completed a minimum of every three years.

pelargonic acid (Scythe): PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gallons per 100 gallons).

Herbicides Used Preemergence to Weeds

acetochlor (Surpass): REI 12h, Group 15.  Not for use in New Hampshire. Works to inhibit weed seed germination, and will not work on emerged weeds.  Labeled for control of annual grasses and broadleaf weeds.  Can be used early preplant, preplant incorporated, preemergence, postplant-preemergence, and early crop postemergence.    Rates based on both soil texture and tillage system used (conventional, reduced, or no-till).  Read label for proper rate selection. Also see label for herbicides approved as tank-mixing partners. 

dimethenamid (Outlook): PHI 50d, REI 12h, Group 15.  May be applied preplant surface, preplant incorporated, preemergence, or postemergence to corn up to 12-inches tall. May be applied as a single application or two split applications.  See Table 2. of product label to select correct rate for your soil texture and organic matter content. A split application may be used (8 to 16 fl oz/A per application, not to exceed 24 fl oz/A per year).  Allow a minimum of 14 days between applications. First application can be applied preplant, preemergence, or postemergence, then apply the remainder (8 to 16 oz/A) of the seasonal maximum rate during the second application (postemergence).  Can be tank-mixed with many other herbicides, see label for details.  Check with seed supplier for potential varietal susceptibility to injury. Outlook is a selective residual herbicide for controlling many annual grasses, annual broadleaf weeds, and sedges as they germinate. Will not control emerged weeds.

pendimethalin (Prowl H2O): REI 24h, Group 3. Apply before weed germination. Emerged weeds will not be controlled.  Work against annual grasses and some broadleaf weeds.  Can be used after planting but before weeds germinate and crop emerges, or after corn emerges until it is 20 to 24-inches tall or at V8.  Rate based on soil texture, see label for details.  When used after planting, there is potential for crop injury if herbicide is moved into the seed zone.  Minimize the potential for crop injury by preparing a firm seedbed and planting corn seed at least 1.5" deep.  If heavy rains follow an application to dry soil, Prowl can move to the seed zone and cause crop injury. Specific weeds for which this herbicide should be considered include triazine-resistant lambsquarters, and velvetleaf. 

pyroxasulfone (Zidua): PHI 37d, REI 12h, Group 15.  A root-and-shoot growth inhibitor that controls susceptible germinating seedlings before or soon after they emerge from the soil. Application rates vary depending on soil texture, see label for details. May be applied preplant surface, pre-plant incorporated, preemergence, or early postemergence to corn for residual preemergence control of weeds. See label for application instructions for each timing.  Plant corn seed at least 1" deep.  Labeled for use against many annual grasses and broadleaf weeds. Controls most annual grasses including crabgrass, panicum, foxtails, and barnyardgrass.  Weak on common lambsquarters but will control redroot pigweed, carpetweed, nightshade, and common purslane.  Has activity on yellow nutsedge. 

s-metolachlor (Dual Magnum)PHI 30d, REI 12h, Group 15.  Can be used either preplant surface, preplant incorporated, preemergence, or lay-by.  See label for application instructions and rates based on timing and soil type. 

simazine (Princep): PHI 45d, REI 12h, Group 5. Apply up to 2 qt/A preplant incorporated or to the soil surface immediately after planting before corn emerges. Use alone only if annual grasses are not a problem.  Do not apply on highly erodible soils unless there is at least 30% plant residue cover. 

Herbicides Used Pre- and Postemergence to Weeds

2,4-D (Amine 4): PHI 45d, REI 28h, Group 4.   Can make one preplant or preemergence application per crop cycle. Apply up to 2.14 pt/A (1.0 lb ae/acre) to soil anytime after planting but before corn emerges. Can make one postemergence application per crop cycle. Apply a maximum of 1.07 pt /A (0.5 lb ae/acre) per application. Use drop nozzles to direct spray toward base if corn is over 8" tall. Do not apply from 7 to 10 days before tasseling to dough stage. Allow a minimum of 21 days between applications. Use a maximum of 3.2 pts/acre (1.5 lbs ae/acre) per year. Reduce rate of 2,4-D if temperature is hot and soil is wet. Use only the amine formulation of 2,4-D; Do not use any ester or low-volatile ester formulations. Use all precautions to avoid spray drift to desirable broadleaf crops.

atrazine (Aatrex 4L): REI 12h, Group 5.  Apply preplant incorporated or to the soil surface immediately after planting. Use alone only if annual grasses are not a problem.  Shallow cultivation may help to control annual broadleaf weeds. May be tank mixed with any of the preemergence grass herbicides listed above as well either glyphosate or paraquat for burndown of existing weeds.

For postemergence applications, add either 1 qt/A of crop oil concentrate or 1 gal/A of spray oil. Apply when weeds are 1 to 1 1/2" high and before corn is 12" high. This treatment can be used as the primary broadleaf herbicide treatment instead of an application at planting or it can be used as an emergency treatment if the soil-applied broadleaf herbicide treatment failed. If applied correctly, this application will control the emerged weeds and will continue to provide residual control for later-emerging broadleaf weeds. Check label for additional precautions regarding the use of crop oil and petroleum oils.

Only 1 lb active ingredient of atrazine is recommended for sweet corn in New England. This is well below the rate on the label and constitutes best management practices for groundwater protection. This rate could be reduced further, although the grower should be prepared to make a second application of atrazine if any weeds escape.

halosulfuron (Sandea): PHI 30d, REI 12h, Group 2.  Apply 2/3 to 1 oz/A over the top or with drop nozzles from the spike through layby stage of the corn.  If necessary, a sequential treatment of this product at 2/3 oz/A acre may be applied only with drop nozzles semi-directed or directed to avoid application into the corn plant whorl.  Do not apply more than 2 applications per year.  Do not use on “Jubilee” sweet corn.  Other varieties may also be sensitive to injury.  The use of non-ionic surfactant is recommended for use on emerged weeds (1 to 2 qt/100 gal spray). Works on germinating broadleaf weed seeds, and also on emerged broadleaf weeds.  Control varies with type and size of weed.  Species listed on the label include redroot pigweed, pokeweed, common ragweed, Pennsylvania smartweed, common sunflower, velvetleaf, wild mustard, yellow nutsedge, and wild radish. Do not cultivate for 7 days after application.

mesotrione (Callisto): PHI 45d, REI 12h,  Group 28.  May be applied by ground for preemergence or postemergence weed control.  See label for list of susceptible species. Callisto provides excellent control of many problem broadleaf species such a velvetleaf and triazine-resistant lambsquarters.  Callisto provides only partial control of yellow nutsedge and no control of ragweed when applied postemergence.

Make a single preemergence application of 6.0-7.7 oz/A after seeding to the soil surface. Can be tank mixed with many other herbicides, and it also included in some premixed products.  See label for details. Use 5 to 6 oz/A if tank mixing with atrazine. In a tank mix, the atrazine rate can be reduced to 0.5 to 1 pt/A.  A grass herbicide must also be used. On cool soils in the spring, Callisto may be a better option than using Prowl to control these two weed species. Callisto does not provide preemergence control of yellow nutsedge. With this weed, it is important to continue to use atrazine (alone or in combination with Callisto) as well as either Dual, Outlook, or Zidua preemergence. See the label for precautions and more information on tank mixes, rates, and weeds controlled.

For postemergence weed control, apply 3 oz/A to corn up to 30" tall when weeds are no more than 3" tall.  Include a nonionic surfactant.  Do not make more than 2 applications per season to corn and do not exceed a total of 7.7 oz/A of Callisto. Applications should be a minimum of 14 days apart.  Use other options if these weeds are present. See the label for precautions and more information on tank mixes, rates, and weeds controlled.  Severe corn injury resulting in yield loss may occur if any organophosphate or carbamate insecticide is applied foliar postemergence within 7 days before or 7 days after Callisto application.  May cause crop bleaching in some yellow popcorn and sweet corn hybrids. Crop bleaching is typically transitory and has no effect on final yield or quality.

Herbicides Used Postemergence to Weeds

The following herbicides are applied after weeds have emerged. They can be used as the only broadleaf weed control to supplement a soil-applied grass herbicide or they can be used as an emergency treatment if the soil-applied broadleaf herbicide fails to provide adequate control. Timing is very important when using these herbicides. Be careful to check both the ideal weed stage of growth as well as the ideal timing and application precautions for the crop.

bentazon (Basagran): PHI 30d, REI 48h, Group 6.  Apply early post-emergence overtop when weeds are small and corn has 1 to 5 leaves. Rate varies based on weed species targeted (1 to 2 pt/A). See label for info. Bentazon will not control redroot pigweed and will provide only partial control of common lambsquarters, giant ragweed and morning glory. Bentazon should be primarily used as an emergency treatment when a soil-applied broadleaf herbicide has failed. There is less chance of adjacent crop injury from spray drift than with 2,4-D.

carfentrazone (Aim EC): REI 12h, Group 14.  Apply 0.5 to 1 oz/A to actively growing weeds anytime from preplanting until corn is at the 14 leaf-collar stage.  Can be broadcast applied until corn reaches the 8 leaf-collar stage.  For application after corn is at the 8 leaf-collar stage, use drop nozzles to avoid spraying into the whorl and on the corn foliage. Tank mix with atrazine at reduced rates or another broadleaf herbicide to increase the spectrum of weeds controlled. Add non-ionic surfactant at a rate of 1 qt/100 gal spray solution. Expect to see speckling of the crop foliage after application. Initially, the injury appears to be substantial, but it is not systemic and the corn outgrows the injury rapidly. Cultivar sensitivity may vary with Aim. Use caution when treating new cultivars. Weather conditions may also affect the degree of injury observed. Injury may be more severe during periods of warm, cloudy weather with high humidity and plentiful soil moisture when corn growth is rapid and soft. Do not apply more than 2 oz/A per season.  Works best before weeds reach 4” tall or rosettes are 3” in diameter.

clopyralid (Stinger): PHI 30d, REI 12h, Group 4.   For postemergence control of weeds in the composite and legume families. Use Stinger for postemergence control of annual sowthistle, Canada thistle, common cocklebur, common sunflower, giant and common ragweed, Jerusalem artichoke, jimsonweed and other broadleaf weeds infesting field corn.  Apply timing and rates specified on the label. Spray additives are not needed or required by the label and are not recommended. Stinger is a postemergence herbicide with some soil residual activity. Observe replant restrictions on the label or injury may occur from herbicide carryover.

fluthiacet-methyl (Cadet): REI 12h, Group 14. Can be applied as a preplant burndown or after corn emerges as a postemergence weed control.  Can be used anytime until corn is 48” tall or until tasseling occurs. Apply to actively growing weeds before they reach the maximum height listed on the product label for each target weed species.  Does not control grasses, but can be tank mixed with many other herbicides.  See label for details.  Do not exceed 1.25 oz/A per season.  Do not apply to crop under stress or injury may occur. 

nicosulfuron (Accent Q):  REI 4h, Group 2. Apply 0.45 to 1.8 oz/A.  Not for use in New Hampshire. Postemergence grass herbicide.  Works on grasses only.  Best results are obtained when broadcast applied to young, actively growing grasses before corn is 12” tall.  If corn is 12" to 18" high, applications should be made with drop nozzles.   Applications must include either a non-ionic surfactant or crop oil concentrate.  An ammonium nitrate nitrogen fertilizer must also be used unless the label of a potential tank mix partner prevents it.  Do not apply if corn is greater than 18" or 5 leaf collars.  Not all sweet corn varieties are tolerant to Accent.  Check with the Dupont representative or Extension for further information.  Also see the label for optimum sizes of grasses.

pelargonic acid (Scythe):  PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gallons per 100 gallons). Use a 3 to 5% solution for annual weeds, a 5 to 7% solution for biennial and perennial weeds, and 7 to 10% solution for maximum burndown. Delivery rate for boom applications should be 75 to 200 gals of spray solution per acre; complete coverage of weed foliage is essential. Use a DIRECTED/ SHIELDED SPRAY; contact with crop will cause injury. For hand-held equipment, spray to completely wet all weed foliage but not to the point of runoff. Repeat applications as necessary. Tank mixes are allowed with this product. See label for complete details.

tembotrione (Laudis):  REI 12h, Group 27.  Apply 3 fl oz of Laudis per acre postemergence to control many annual broadleaf weeds, including common lambsquarter and triazine-resistant broadleaf weed biotypes, and many annual grasses.  Add oil methylated seed oil (MSO) or concentrate (COC) to be 1% of the spray solution (1 gal/100 gals of spray solution).  In addition, the label requires the addition of nitrogen liquid fertilizer (1.5 qt/A) or AMS (1.5 lb/A).  Tank mix with 0.25 to 1 lb ai/A of atrazine for improved control and to broaden the spectrum of weeds control.  Local university data supports the use of at least 0.5 lb ai/A of atrazine. 

Do not apply tank-mixes of Laudis and atrazine to corn greater than 12" tall.  Do not use postemergence if Callisto, Lumax or Lexar was used preemergence.  Do not tank-mix with Callisto.  Laudis will control/suppress most annual grass species, but may not control certain grass species or grasses larger than the maximum recommended size when treated.  Fall panicum is not controlled by Laudis.  Most broadleaf weeds should be treated before they are 6" tall and grass weeds should be treated before 2" in height.  Laudis has up to an 18 month replant restriction for many vegetables.

tolpyralate (ShieldEx 400 SC): PHI 35d, REI 12h, Group 27. Can control or suppress the growth of many young and actively growing broadleaf and grass weeds. See label for list of susceptible weeds. Apply up to 1.35 fl oz/A when corn is up to the 6 leaf collar (V6) stage or up to 20 inches tall, whichever is more restrictive. Up to two applications are permitted at least 14 days apart. Not to exceed 2.7 fl oz/A per year. Use an adjuvant for optimum activity (refer to adjuvant section of label for details). Rainfast within 1 hour after application.

topramezone (Armezon): PHI 45d, REI 12h, Group 27.  Absorbed by leaves, roots, and shoots and translocated to the growing points of sensitive weeds to control emerged weeds. Crops under stress may show transient bleaching. These symptoms are temporary and occur infrequently.  Apply up to 1 oz/A when weeds are actively growing, up until corn stage V8.  Controls many annual broadleaf weeds, including common lambsquarter and triazine-resistant broadleaf weed biotypes, and annual grasses.  Postemergence applications of Armezon require the addition of an adjuvant (crop oil concentrate) and nitrogen fertilizer for optimum weed control. Do not use postemergence if Callisto, Lumax or Lexar was used preemergence due to herbicide resistance concerns.  Will control/suppress annual grass species and broadleaf weeds, but may not control species when larger than the maximum recommended size for treatment.  Most broadleaf weeds should be treated before they are 6" tall and grass weeds should be treated before 2" in height.  Use the higher rate to suppress or control panicum species or in rescue applications where the target weeds have grown beyond the size indicated on the label.  Can be tank mixed with 0.25 to 1 lb ai/A of atrazine for improved control and to broaden the spectrum of weeds control.  Local university data supports the use of at least 0.5 lb ai/A of atrazine. 

Perennial Weed Control

Several perennial weed species, including quackgrass, bindweed and milkweed, may be present in a corn field. The grass and broadleaf herbicides described above will have limited activity on these weeds. Use of glyphosate as described below can provide excellent control of these perennial weed species.

glyphosate (Roundup Power Max): REI 12h, Group 9. Apply as a spot treatment BEFORE silking of corn. Do not treat more than 10% of the total field area to be harvested. Any crop plants receiving spray in the treated area will be killed.

Apply AFTER corn harvest to actively growing quackgrass 6" to 8" high. Wait at least 5 days and then plow. Do not plant subsequent crops other than those on the label for 30 days following application. Most effective on bindweed and milkweed at or after bloom.

Mixing Herbicides for Weed Control in Sweet Corn

Many corn herbicides can be tank mixed with one or more other herbicides to extend the spectrum of weed control.  Labels will have detailed instruction about compatible tank mixing partners and instructions on selecting rates, etc. when tank mixing.

Formulated Mixes (Prepackaged Tank Mixes)

In recent years, many products have come on the market as prepackaged combinations of herbicides which were often recommended in the past as tank-mix combinations of products purchased separately. They are designed for to expand the spectrum of control (i.e. grass herbicide mixed with broadleaf herbicide). 

There are 3 questions that a grower or pesticide applicator should ask when deciding whether to use a formulated mix or the individual herbicide.

  1. Which is less expensive on a per acre basis?
  2. Which formulation is easier to apply? Most pesticide applicators prefer to avoid wettable powders, for example.
  3. Is the ratio of the two herbicides in the formulated mix appropriate for the given field situation? For example, Bicep Lite contains 2/3 as much atrazine as Bicep and should allow growers a better opportunity to obtain good grass control without using more atrazine than is needed.

Following are some examples of formulated mixes registered for use on sweet corn. There are many others in addition to those listed.

Formulated Mix individual Herbicides Contained in Mix
Acuron atrazine (Aatrex, Group 5) + s-metolachlor (Dual, Group 15) +mesotrione (Callisto, Group 27) + Bicyclopyrone
Anthem fluthiacet-methyl (Cadet, Group 14) + pyroxasulfone (Zidua, Group 15)
Armezon Pro topramezone (Armezon, group 27) + dimethenamid (Outlook, Group 15)
Bicep Magnum
Bicep Lite Magnum (Aatrex)
metolachlor (Dual, Group 15) + atrazine (Aatrex, Group 5)
Laddock bentazon (Basagran, Group 6) + atrazine (Aatrex, Group 5)
Lexar and Lumax atrazine (Aatrex, Group 5) + metolachlor (Dual, Group 15) + mesotrione (Callisto, Group 27)