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 26 and Fungicides and Bactericides Alphabetically Listed 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)

Symptoms and the appearance of lesions can differ by pathogen. Lesions will appear on leaves, leaf sheaths, and husks. Plant resistant varieties. Improve air circulation by increasing plant spacing and choosing sites with good air flow. 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 in the same FRAC Group.

• azoxystrobin (Quadris F aka Abound F): 6.0 to 15.5 fl oz/A; PHI 7d, REI 4h, Group 11. See label for restrictions. 
• azoxystrobin plus propiconazole (Quilt): 7.0 to 14.0 fl oz/A; PHI 14d sweet corn, 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. Sweet corn only.
• fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.
• mancozeb (Dithane F45): 1.5 qt/A; PHI 7d, REI 24h, Group M03. 
• propiconazole (Tilt): 2.0 to 4.0 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 24h, Group 3.
• pyraclostrobin (Headline): 6.0 to 12.0 fl oz/A; PHI 7d, REI 12h, Group 11.
• pyraclostrobin plus metconazole (Headline AMP aka BAS 556 SC): 8.0 to 10 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 (spores) 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 in the same FRAC Group.

• azoxystrobin (Quadris F aka Abound F): 6.0 to 15.5 fl oz/A; PHI 7d, REI 4h, Group 11. See label for restrictions.
• azoxystrobin plus propiconazole (Quilt): 7.0 to 14 .0fl oz/A; PHI 14d sweet corn, 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. Sweet corn only.
• fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.
• mancozeb (Dithane F45): 1.5 qt/A; PHI 7d, REI 24h, Group M03. 
• propiconazole (Tilt): 2.0 to 4.0 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 24h, Group 3.
• pyraclostrobin (Headline): 6.0 to 12.0 fl oz/A; PHI 7d, REI 12h, Group 11.
• pyraclostrobin plus metconazole (Headline AMP aka BAS 556 SC): 8.0 to 10 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 corn, 30d popcorn, REI 12h, Groups 11 &3.

Rust (Puccinia spp.)

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 appear as blister-like pustules called uredinia on the leaf epidermis. 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 from the same FRAC Group.

• azoxystrobin plus propiconazole (Quilt): 10.5 to 14 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.
• benzovindiflupyr (Trivapro A): 13.7 fl oz/A (see label); PHI 14d, REI 12h, Groups 3, 7 & 11.
• 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. Sweet corn only.
• fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.
• mancozeb (Dithane F45 ): 1.5 qt/A; PHI 7d, REI 24h, Group M03.
• propiconazole (Tilt): 4.0 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 24h, Group 3. 
• pyraclostrobin (Headline): 6.0 to 12.0 fl oz/A; PHI 7d, REI 12h, Group 11.
• pyraclostrobin plus metconazole (Headline AMP): 8.0 to 10 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 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. Symptoms will appear as galls on the ears or stalks and contain black teliospores. Fungicides will not provide effective control of common smut.

Stalk Rots (Gibberella, Stenocarpella, Macrophomina, Colletotrichum & Fusarium spp.)

Fungal stalk rots continue to be serious diseases of corn. Their occurrence and severity vary from year to year. Early on, plants may wilt, and later symptoms may be leaf discoloration, browning of lower stalk, and the pith becoming hollow. 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 varietal susceptibility, 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. Symptoms will include narrow lesions, 5 cm or greater, that will have wavy margins. 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. Early symptoms are chlorotic spots and streaks; leaves will later develop a mosaic pattern. 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, as peach is an overwintering host of the green peach aphid.

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 27 and Insecticides Alphabetically Listed 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.

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 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 75-100 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 various host plants, preferring whorl-stage corn to older corn. Eggs hatch in 2-10 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 inches. 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 2-4 weeks and the vapor strip every 6-8 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 randomly, 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. A control is needed if 15% or more of plants are infested with FAW.
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 insufficient for treatment. Outbreaks are not common in New England but do occur occasionally and can cause significant damage.

• alpha-cypermethrin (Fastac* CS): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.
• Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Use alone to control light populations or 1st and 2nd 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 DF^OG): 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): 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A. For 1st and 2nd instar only.
• Burkholderia spp. strain A396 (Venerate XC^OG): 1 to 4 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. FAW only.
• chlorantraniliprole (Coragen): 3.5 to 7.5 oz/A; PHI 1d, REI 4h, Bee: L, Group 28. For foliar applications.
• chlorantraniliprole plus lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 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 1st and 2nd 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. Use higher rate for large larvae.
• 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. FAW 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.
• 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 SC^OG): 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*): 2.8 to 4 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 bugs.  

• acetamiprid (Assail): 5.3 oz./A; PHI 7d, REI 12 h, Bee: M, Group 4A. Suppression only.
• bifenthrin (Brigade* 2EC): 2.1 to 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. There are pockets of overwintering populations in eastern NY and southern New England. The heaviest numbers are found in coastal areas and up the major river valleys. The severity of infestations varies yearly and may change suddenly during the season. CEW feeds in a wide range of crops; 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, a dark band near the margin of the hind wing, and a 1.2-1.5" wingspan. Live and newly dead 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 2.5-6 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. CEW larvae may be brown, tan, green, or pink, with light and dark longitudinal stripes, and reach 1.5-2" when fully 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 flight changes and 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 the 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 3-6 days, depending on trap captures, according to the chart below. If the maximum daily temperature is below 85º F for 2-3 days, spray intervals may be extended by 1 day. Continue treatments until 5-7 days before final harvest or until the 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

Bt hybrids that express the insect toxin found in Bacillus thuringiensis (Bt) in leaves, husks, and kernels offer protection against CEW, but may require additional insecticide applications to control this pest. Hybrids containing the Viptera trait are currently very effective at controlling CEW.

• alpha-cypermethrin (Fastac* CS): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.
• Bacillus thuringiensis aizawai (XenTari^OG): 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 XC^OG): 1 to 4 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/A; PHI 1d, REI 4h, Bee: L, Group 28. For foliar applications.
• chlorantraniliprole plus lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 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. For control before larvae bore into plant stalk or ear.
• 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, 0.33 to 0.5 lb/A for whorl as needed; PHI 21d, 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 formulation. May not provide effective control under high corn earworm pressure. Effective as ovicide and larvicide.
• methoxyfenozide plus spinetoram (Intrepid Edge): 8 to 12 fl oz/A; PHI 3d ears, REI 4h, Bee: M, Groups 5 & 18. Apply as broadcast or direct spray to ear zone. Ensure thorough wetting of the silks. A 2-day re-treatment schedule may be necessary at silking.
• nuclear polyhedrosis virus of Helicoverpa zea (Gemstar^OG): 4 to 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 Oil^OG): 2 gal/A applied when insects first appear (repeat weekly for additional control), 0.5 ml applied by hand directly to silk within 6 to 7 days after 50% of the ears are silking; PHI 0d; 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 SC^OG): 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*): 2.8 to 4 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 colonizes whorl leaves and the immature tassel. Populations may become numerous enough to interfere with pollen shed, stunt plants, and 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 encourages the growth of sooty mold fungus. The presence of aphids and honeydew on corn husks reduces their marketability. Varieties with purple or green tassels seem less susceptible to aphid build-up than those with yellow tassels. Ample rainfall or irrigation during the silk stage can reduce or eliminate aphid populations. 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 June 10 are generally not bothered by CLA. 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.

• acetamiprid (Assail): 2.1 to 2.9 oz./A; PHI 1d, REI 12h, Bee: M, Group 4A.
• alpha-cypermethrin (Fastac CS*): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 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. For optimum results, direct spray at the aphid population to achieve maximum coverage of the exposed insects. Aphids not contacted by the spray, such as in whorls and leaf axils, may not be adequately controlled.
• 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, 3d if used for forage, REI 48h, Bee: H, Group 1A. Some sweet corn varieties may be damaged by methomyl.
• petroleum oil (Suffoil X^OG): 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" long. Moths from the South arrive between March and June. Eggs are laid mostly on grasses and winter annual weeds, usually near field areas prone to flooding. Certain fields tend to have a history of repeated cutworm damage. The larvae feed after dark and hide under the soil surface during the day. There are 2-3 generations per year, but usually only the first generation, which produces larvae in May and June, damages corn. Small larvae feed on leaves; larger larvae occasionally 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, apply insecticides between midnight and dawn while cutworms feed 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* CS): 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 plus tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A & 1B. Must be incorporated into soil to at least 1" depth. Apply at planting as band or in-furrow.
• 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; PHI 1d, 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. Black cutworm only for PPI and PRE applications.
• bifenthrin plus Bacillus amyloliquefaciens strain D747 (Ethos XB): 3.4 to 17 fl oz/A; PHI 1d, REI 12h, Bee: H, Groups 3A & BM02. Apply as a 5-7 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 as broadcast from 3 days before planting to at-planting time. Immediately incorporate immediately into top 2" of soil.
• gamma-cyhalothrin (Declare*): 0.10 to 0.18 oz/1000 row ft for at-plant soil application in T-band or band only, 0.26 oz/1000 row ft permitted for at-plant soil application in New Hampshire only, 0.77 to 1.28 oz/A foliar; PHI 21d, 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 formulation. Variegated cutworm only.
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.
• spinosad (Seduce^OG): 20 to 44 lb/A or 0.5 to1 lb/1000 sq ft; PHI 1d, REI 4h, Bee: M, Group 5. Spread bait on soil around plants. Reapply after heavy rain or at least every 2-4 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 at planting.
• 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*): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

European Corn Borer (Ostrinia nubilalis)

European corn borer (ECB) is a resident pest with 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 beans, peppers, and potatoes. 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 GDD). 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 residue 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 striae, a tiny parasitic wasp that attacks ECB eggs, can reduce the need for insecticide applications. See Table 23, 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 50-100 plants in groups of 5-20 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 infestation levels, 2 applications may be needed to provide control. The use of selective products to control ECB will conserve natural enemies of aphids and ECB.

Corn started under plastic or row cover often reaches the 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 stage 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 ECB and may not require additional insecticide applications, but scouting is still recommended to assess ECB and other pests.

• alpha-cypermethrin (Fastac* CS): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.
• Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. See the general recommendations for Bt kurstaki below. For resistance management, may be rotated with Bt kurstaki products.
• Bacillus thuringiensis kurstaki (Dipel DF^OG): 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 (4-5 days) and high rates under high ECB pressure. For resistance management, may be rotated with Bt aizawai (XenTari).
• Burkholderia spp. strain A396 (Venerate XC^OG): 1 to 4 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/A; PHI 1d, REI 4h, Bee: L, Group 28. For foliar applications.
• chlorantraniliprole plus lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 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 on ears 1 to 3 days or as needed; 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 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 plus spinetoram (Intrepid Edge): 4 to 12 fl. oz./A; PHI 3d, REI 4h, Bee: M, Groups 5 & 18. Direct application at the whorl for early-season infestations.
• 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 SC^OG): 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*): 2.8 to 4 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, feeding and laying eggs in the soil. Direct feeding damage is not significant, but economic damage can be caused by the bacterial disease Stewart’s 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 <90ºF, intermediate if 90-100º F, and destructive if >100ºF. 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 in 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.

• acetamiprid (Assail): 4 to 5.3 oz./A; PHI 7d, REI 12 h, Bee: M, Group 4A.
• alpha-cypermethrin (Fastac* CS): 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.
• 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 plus 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. Phytotoxicity may occur on some varieties.
• 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. Granules must be incorporated into the soil. 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*): 2.24 to 4 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 CEW.

• acetamiprid (Assail): 5.3 oz./A; PHI 7d, REI 12h, Bee: M, Group 4A.
• alpha-cypermethrin (Fastac* CS): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A. Adults only.
• 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 plus lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A. Adults only.
• 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 EC5.0^OG): 4.5 to 15.61 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*): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A. Adults only.

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

Sap beetle problems are more likely to occur on farms producing various 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 European 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. The 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 2-4 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 the tip cover's length and tightness are important to reduce infestations. Some varieties with long, tight tip covers 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 with 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, including 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 to bury ears at least 4" deep if infestations are high.

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 6-7 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.

• acetamiprid (Assail): 4-5.3 oz/A; PHI 1d, REI 12h, Bee: M, Group 4A.
• alpha-cypermethrin (Fastac* CS): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A. Adults only.
• 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.
• chlorantraniliprole plus lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A. Adults only.
• esfenvalerate (Asana* XL): 5.8 to 9.6 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.
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A. Adults 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.
• zeta-cypermethrin (Mustang*): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A. Adults only.

Seedcorn Maggot (Delia platura)

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

• beta-cyfluthrin plus tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A & 1B. Must be incorporated into soil to at least 1" depth. Apply at planting as band or in-furrow.
• 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 1d, 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 21d, 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 ft; PHI 30d, REI 48h, Bee: H, Group 1B. Apply in a 7" band over the row at planting and lightly incorporate. Granules must be incorporated into the soil. 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 at planting.
• 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. This pest overwinters as eggs 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 grass 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 1 generation per year. Reduced tillage fields, which may have higher levels of grassy and broadleaf weeds, may result in increased levels of stalk borer. To reduce overwintering eggs, prevent or eliminate grassy weeds, especially after July. 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 plus lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 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. For control before larvae bore into plant stalk or ear.
• 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.

Western Bean Cutworm (Striacosta albicosta)

Western bean cutworm (WBC) is a late-season pest of corn that causes direct physical damage to corn and leaves plants more susceptible to pathogens. WBC is native to the US corn belt and has been moving eastward since the early 2000s. WBC has 1 generation per year. Adults begin emerging in June, with peak flight occurring from July through early August. Egg-laying and plant damage occurs August-October.

Adults look similar to other cutworm moths and corn pests but can be distinguished by a long white stripe that runs along the edge of the forewings. Other diagnostic characteristics include a small white dot in the middle of the forewing and a larger U-shaped brown spot further back on the forewing. Adults also have long antennae (⅓-½ length of the body). Adult moths are active at night.

Larvae also look similar to other caterpillar corn pests, but the most prominent difference is 2 dark brown rectangles directly behind the brown head capsule and a lack of black netting on head capsule.

Females lay about 50 white eggs in masses on upper surfaces of corn leaves prior to tasseling. The eggs turn purple about 24 hours before hatching. The caterpillars are very mobile and undergo 6 instars in a month before dropping to the soil to overwinter in a prepupal stage and then pupate in the spring. The 1st-3rd instars of WBC feed on leaf axils, pollen, and corn silks, then bore into the ear during the 4th instar where they continue feeding on kernels.

Pheromone traps can be used to monitor adult activity. It’s best to scout corn tassels prior to pollen shed and upper leaf surfaces of new leaves for egg masses. Emergence holes from larvae that bored into ears can be seen in dry husks after harvest. There is also a NEWA model for WBC to help with timing of insecticide applications around moth activity and when to scout for egg masses and newly hatched larvae. Sprays will be ineffective once larvae bore into ears. Treatment is usually recommended when 95% of corn has tassels and 70-90% of egg masses have hatched

• beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.
• Burkholderia spp. Strain A396 cells and spent fermentation media (Venerate XC^OG): 1 to 4 qt/A; PHI 1d, REI 12h, Bee: H, Group UN.
• chlorantraniliprole plus lambda-cyhalothrin (Beseige*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Group 28 & 3A.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.
• methoxyfenozide (Intrepid 2F): 4 to 16 fl oz/A; PHI 3d, REI 4h, Bee: L, Group 18. Apply at first sign of feeding damage.
• methoxyfenozide plus spinetoram (Intrepid Edge): 4 to 12 fl oz/A; PHI 3d, REI 4h, Bee: M, Groups 18 & 5. Apply at first sign of feeding damage. 

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 2 years after the sod has been broken. Summer fallow is recommended for at least 1 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 plus tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A & 1B. Must be incorporated into soil to at least 1" depth. Apply at planting as band or in-furrow.
•  
• 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 6-7" band over closed seed furrow at-planting, 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*): 0.041 to 0.82 oz/1000 row ft for at-plant soil application, 0.26 oz/1000 row ft permitted for at-plant soil application in New Hampshire only; PHI 21d, REI 24h, Bee: H, Group 3A. Suppression only for wireworms. For white grub control in CT, ME, MA, RI, and VT: use for reducing damage when used as T-band or in-furrow on light to moderate infestations. Use 0.14 to 0.18 oz/1000 row ft for moderate infestations. For high infestations, use a premium soil insecticide.
• 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. granules must be incorporated into the soil. 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, apply as in-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, European chafer, and May/June beetle larvae, and true white and annual white grub).

NOTES: 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 3-5" 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.

Herbicide Options

Stale Seedbed

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 in the Weed Management section). If a grower is using a minimum- or no-till system, 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*): 2 to 4 pts/A. REI 12h, Group 22. 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. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
• pelargonic acid (Scythe): PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gal/100 gal).

Preemergent Herbicides (before weeds germinate)

• acetochlor (Surpass): REI 12h, Group 15. Apply 1.5-3.17 pt/A per application. Do not exceed 1.5-3.17 pt/A per year. Rates based on soil texture and tillage system used (conventional or reduced- or no-till). Do not apply to sandy soils or within 50’ of any well where the depth to groundwater is 30’ or less. Apply in a minimum of 10 gal/A of spray. Can be applied to the soil surface up to 30 days before planting, but for best results, apply as close as possible to planting and prior to weed emergence. Do not apply after sweet corn has emerged. Cultivation should be delayed as long as possible after applying or the herbicide may be diluted. Can also be applied to the soil surface and incorporated into the top 2” of soil anytime up to 14 days before planting. Poor soil tilth or excessive crop residue may reduce control. Do not move soil after incorporation. Can also incorporate into the soil with 0.25” of water within 7 days of application before or after planting corn, as long as corn has not emerged.
• dimethenamid (Outlook): PHI 50d, REI 12h, Group 15. Apply 8-24 oz/A per application, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 24 oz/A per year. If applying a split application, use 8-16 oz/A for the first application and the remaining 8-16 oz/A for the second application. Rate based on soil texture and percent organic matter. Can be applied before up to 45 days before planting, after planting but before emergence, or after crop emergence until corn is 12” tall. If applying 15-45 days before planting, use a higher rate and apply as part of a split-application program where the second application is made after planting. If applying 2 weeks before planting or after planting but before crop emergence, incorporate 1-2" into the soil with shallow cultivation or water through irrigation or rainfall.
• pendimethalin (Prowl H2O): REI 24h, Group 3. Apply 2-4 pt/A per application, only 1 application per year. Rate based on soil texture. Can be applied after planting but before weeds and crop emerges, or after corn emerges until it is 20-24” tall or at the V8 growth stage. Use drop nozzles to direct spray to the soil surface if applying after crop emergence. When applying after planting but before emergence, 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 and covered with soil. May cause crop injury if heavy rains follow an application to dry soil.
• pyroxasulfone (Zidua): PHI 37d, REI 12h, Group 15. Apply 1-4 oz/A per application, multiple applications allowed per year. Do not exceed 2.75-5 oz/A per year. Rate based on soil texture. Can be applied before planting, after planting but before corn emerges, or early after corn has emerged. Plant corn seed at least 1" into the soil. If applying from 14 days before planting until the V4 stage, apply broadcast and do not incorporate. Do not apply earlier than 14 days before planting for sweet corn. For popcorn, can be applied in the fall or winter to manage winter annual weeds, up until 14 days before planting, and in that case, incorporate less than 2” into the soil with shallow tillage.
• s-metolachlor (Dual Magnum): PHI 30d, REI 24h, Group 15. Apply 1.33-2.6 pts/A per application, multiple applications allowed per year, a minimum of 14 days apart. Do not exceed 3.9 pts/A per year. Rate based on application timing, soil texture, and percent organic matter. Can be applied before planting, after planting but before crop emergence, or at lay-by. To target glyphosate resistant Italian ryegrass, apply to the soil surface after harvest from September 1- December 1. Do not apply to frozen ground. The combined applications in the fall plus spring must not exceed the maximum allowed annual rate. Only 1 fall application per crop cycle. Can apply in the early spring between 14 and 30 days before planting, or after planting but before crop emerges. Do not till deeper than 2-3” after application. If applying within 14 days of planting, only incorporate 2” into the soil. Incorporate if dry weather is expected. Reduce soil movement after application for improved weed control. Apply and incorporate after bed formation if planting into beds. Can also be applied after corn has emerged until it is 40” tall. For best results, direct towards the base of corn plants, when they are more than 5” tall.
• 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.

Pre- and Postemergent Herbicides

• 2,4-D (Amine 4): PHI 45d, REI 48h, Group 4. Apply 1-2 pt/A per application, multiple applications allowed per year, a minimum of 21 days apart. Do not exceed 3.15 pts/A per year. Can make 1 application before planting or before corn emergence. Can make 1 application after corn emergence. Do not till for at least 7-10 days after application. Do not use on sandy soil or unacceptable crop injury may occur. Plant corn a minimum of 7 days after application at 1 pt/A and a minimum of 14 days after application at 2 pts/A. In reduced-till systems, apply after corn is planted but before it has emerged. The seed furrow must be completely closed at application. Can also apply when corn is less than 8” tall, as long as leaves have not just unfolded. Use drop nozzles to direct spray toward base of corn if it is over 8" tall. Do not apply from 7-10 days before tasseling through dough stage. Do not apply to open whorls. Reduce rate 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 2.4-4 pts/A per application, up to 2 applications allowed per year, 1 before corn emergence and 1 after. Do not exceed 5 pt/A per year. Can be applied before planting and incorporated into the soil less than 2 weeks before planting, or applied to the soil surface immediately after planting, or after corn emergence until it is 12” high. Do not move treated soil out of the row or move untreated soil to the soil surface or weed control will be diminished. If applying after corn and weeds have emerged, add either 1 qt/A of crop oil concentrate or 1 gal/A of spray oil. Apply when weeds are 1-1.5" 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. On highly erodible soils with less than 30% residue cover at planting, use a maximum of 3.2 pts/A. It is recommended to only use 2 pts/A in all of Massachusetts.
• halosulfuron-methyl (Sandea): PHI 30d, REI 12h, Group 2. Apply 0.67-1 oz/A per application, up to 2 applications allowed per year. Do not exceed 2 oz/A per year. Can be applied over the top of corn, or with drop nozzles from the spike through layby stage of the corn. If making sequential applications, the second application should be at 0.67 oz/A, applied only with drop nozzles semi-directed or directed to avoid application into the corn plant whorl. Do not use on “Jubilee” sweet corn. Has not been tested on all varieties; crop tolerance should be verified before treating the entire field. 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, as well as emerged broadleaf weeds.
• saflufenacil (Sharpen): REI 12h, Group 14. Apply 2 oz/A per application, multiple applications allowed per year, a minimum of 14 days apart. Do not exceed 6 oz/A per year. Can be applied as a burndown herbicide, up to 14 days before planting, or after planting before crop has emerged. Do not apply after corn emergence or severe crop injury will occur. Can incorporate 1-2’’ into the soil if applying before planting. Apply at 1 oz/A before corn has emerged. No residual weed control will occur. If applying as a burndown, apply 1 oz/A with an appropriate adjuvant. Not for sweet corn grown for fresh market—processing sweet corn varieties only. Has not been tested on all varieties; crop tolerance should be verified before treating the entire field. Do not apply to course-texture soils with less than 3% organic matter. Plant corn at least 0.5” deep and ensure the seed row is closed to reduce risk of crop injury. May result in delayed crop emergence and stunting in cool wet conditions after application.
• mesotrione (Callisto): PHI 45d, REI 12h, Group 27. Apply 3-7.7 oz/A per application, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 7.7 oz/A per application. Can make 1 application before corn emergence and 1 after emergence, or 2 applications after corn emergence. If applying before corn has emerged, apply 6-7.7 oz/A to the soil surface after seeding, with 10-30 gal/A of spray. If applying after crop emergence, apply when corn is less than 30” tall or at the 8-leaf stage. Apply up to 3 oz/A per application (if making 2 post-emergence applications, the maximum rate is 6 oz/A per year). Applying after crop emergence may cause crop bleaching in some sweet corn varieties, but typically has no effect on final yield. Adjuvant restrictions apply to sweet corn applications. 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.

Postemergent Herbicides (after weeds germinate)

• bentazon (Basagran): REI 48h, Group 6. Apply 0.8-1.6 pts/A per application, multiple applications allowed per year. Do not exceed 3.2 pts/A per year. Rate based on weed composition. Apply to actively growing weeds when corn has 1-5 leaves and weeds are small. Do not apply to crops subjected to stress conditions such as insufficient moisture or hot or cold temperature, or crop injury may result. Do not graze corn for at least 12 days after treating. An effective treatment in an emergency situation to control certain broadleaf weeds and fairly effective against yellow nutsedge when 4-6" tall. There is less chance of adjacent crop injury from spray drift than with 2,4-D.
• carfentrazone (Aim EC): PHI 14d, REI 12h, Group 14. Apply 0.5-1 oz/A per application, multiple applications allowed per year. Do not exceed 2 oz/A per year. Can be applied as a preplant burndown 1 day after planting by seed up until corn is at the 14 leaf-collar stage. For best results, make application to actively growing weeds up to 4” tall and rosettes less than 3” across. Use drop nozzles to avoid spraying into the whorl and on the corn foliage. 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. Has not been tested on all varieties; crop tolerance should be verified before treating the entire field. 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.
• clopyralid (Stinger): PHI 30d, REI 12h, Group 4. Apply 5-11 oz/A per application, multiple applications allowed per year, a minimum of 21 days apart. Do not exceed 11 oz/A per year. Apply anytime between corn emergence until it is 18” tall in 10-20 gal/A of spray. Rate based on weed composition. Do not cultivate before or after application, if cultivation is necessary, wait 14-20 days after application. Spray additives are not recommended.
• clopyralid (Clean Slate): PHI 30d, REI 12h, Group 4. Apply 0.33-0.67 pts/A per application, only 1 application per year. Apply 0.25-0.5 pts/A of this product from weed emergence up to the 5-leaf stage of weed growth. To target Canada thistle, apply up to 0.67 pts/A as a broadcast treatment to the entire infested area when the majority of thistle plants have emerged (rosette to 8") and thistles are at least 6-8" in diameter or height up to bud stage. Cultivation can disrupt translocation to the roots of Canada thistle, so for best control, do not cultivate before or after application for 14-20 days.
• fluthiacet-methyl (Cadet): PHI 40d, REI 12h, Group 14. Apply 0.6-0.9 oz/A per application. Do not exceed 1.25 oz/A per season. Can be applied as a preplant burndown or after corn emerges until corn is 48” tall or until tasseling occurs. Do not cultivate within 2 days before or after applying. Do not irrigate or apply within 4 hours before a rainfall as it will wash off the Cadet. Does not control grasses, but can be tank mixed with many other herbicides. See label for details. Do not apply to severely stressed or wet crop.
• glyphosate (Roundup Power Max): PHI 7d, REI 12h, Group 9. Apply 15 oz to 3.1 qts/A per application, multiple applications allowed per year. Do not exceed 5 qts/A per year. Rate based on target weed species. Can be applied after crop emergence as a broadcast spray in Roundup Ready varieties or with a completely enclosed hooded sprayer after the corn is 12” tall in non-Roundup Ready varieties. If applying in non-roundup-ready corn varieties, avoid any contact of herbicide with crop or crop death could result. Can be applied 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. Can also be applied after corn harvest to actively growing quackgrass 6-8" tall. Wait at least 5 days after application before plowing. Can be used after harvesting corn but the application must be made a minimum of 30 days prior to planting any crop not listed on the label. Glyphosate is the only postemergent herbicide that can provide excellent control of perennial weed species commonly found in corn, including quackgrass, bindweed, and milkweed. Most effective on bindweed and milkweed at or after bloom.
• nicosulfuron (Accent Q): PHI 70d, REI 4h, Group 2. Not for use in NH. Apply 0.45-1.8 oz/A, only 1 application per year. Do not exceed 1.8 oz/A per year. Best results are obtained when broadcast-applied before corn is 12” tall to young, actively growing grasses. If corn is 12-18" tall, applications should be made with drop nozzles. Do not apply if corn is greater than 18". Has not been tested on all varieties; crop tolerance should be verified before treating the entire field. If organophosphate insecticide (IRAC Group 1B) has been applied to corn, crop injury may occur. Do not use if the crop exhibits herbicide injury from previous applications. Applications must include either a non-ionic surfactant, crop oil concentrate, or an ammonium nitrate nitrogen fertilizer.
• paraquat (Gramozone SL 3.0*): REI 12h or 24h based on application type, Group 22. Apply 0.7-2.7 pts/A per application, up to 3 application before planting or corn emergence and 3 applications after corn emergence are allowed, a minimum of 7 days apart. Do not exceed 8 pts/A (preplant/preemergence), 4 pts/A (after corn emergence), or 1.3 pts/A (harvest aid). Apply in a banded over-row or broadcast application in a minimum of 10 gal/A of spray before corn emergence. Seed with a minimum amount of soil disturbance. After corn emergence, apply with a directed spray (hooded or shielded) or without a directed sprayer when corn is at least 10" tall and nozzles spray no higher than 3" of corn stalk or 1/3 of the corn stalk if corn is over 20" tall. Rate is dependent on weed composition and application use. May be fatal if swallowed or inhaled. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
• pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0. Apply a 3-10% solution (3-10 gal per 100 gal). Rate based on target weed species. Apply in 75-200 gal/A of spray or with a spot sprayer until foliage is wet but not to the point of runoff. Repeat applications as necessary. Can apply for vegetative burndown during site preparation, prior to crop emergence from soil, as a directed and shielded spray during crop growth taking care to avoid contact with foliage and green tissue of crops, or after harvest.
• sethoxydim (Poast): PHI 45d for grain and fodder, 30d for fresh, REI 12h, Group 1. Apply up to 1.5 pt/A per application, multiple applications allowed per year, a minimum 10 days apart. Do not exceed 3 pt/A per year. Use only with Poast Protected sweet corn hybrids. Apply until the onset of pollen shed. Do not apply after pollination. Use with crop oil concentrate (2.0 pt/A) or methylated seed oil (1.5 pt/A). Note that crop oil can cause injury under hot and humid conditions. Can also be used as a spot-spray by mixing 1-1.5% (1.3-1.9 oz/gal) Poast and 1% v:v crop oil concentrate (1.3 oz/gal). Spray to wet, but do not allow runoff of spray solution.
• tembotrione (Laudis): REI 12h, Group 27. Apply 3 oz/A per application, only 1 application per year for sweet corn, up to 2 applications allowed per year for popcorn, a minimum of 7 days apart. Do not exceed 3 oz/A per year for sweet corn or 6 oz/A per year for popcorn. Can be applied after corn emergence until the V7 stage for sweet corn and V8 stage for popcorn. Can also be used as a burndown application after corn harvest, but maximum use rates still apply. Add oil methylated seed oil or concentrate to be 1% of the spray solution (1 gal/100 gal of spray solution). In addition, the label requires the addition of nitrogen liquid fertilizer (1.5 qt/A) or AMS (1.5 lb/A). Do not apply tank-mixes of Laudis and atrazine to corn greater than 12" tall. Do not use if Callisto, Lumax, or Lexar was used preemergence, due to herbicide resistance concerns. Most broadleaf weeds should be treated before they are 6" tall and grass weeds before they are 2" tall. Has not been tested on all varieties; crop tolerance should be verified before treating the entire field. Do not use on Merit or Shogun corn varieties.
• tolpyralate (ShieldEx 400 SC): PHI 35d, REI 12h, Group 27. Apply up to 1.35 oz/A per application, up to 2 application allowed per year, a minimum of 14 days apart. Do not exceed 2.7 fl oz/A per year. Apply when corn is emerged up to the V6 stage or up to 20” tall, whichever is more restrictive. Use an adjuvant for optimum activity. Rainfast within 1 hour after application.
• topramezone (Impact): PHI 45d, REI 12h, Group 27. Apply 0.75-2 oz/A per application, multiple applications allowed per year. Do not exceed 2 oz/A per year. Apply when weeds are actively growing, after corn has emerged up until the V8 stage. Crops under stress may show transient bleaching. These symptoms are temporary and occur infrequently. Do not use postemergence if Callisto, Lumax, or Lexar was used preemergence due to herbicide resistance concerns. Most broadleaf weeds should be treated before they are 6" tall and grass weeds before they are 2" tall. May not control species when larger than the recommended size for treatment. Rainfast within 1 hour after application.

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 to expand the spectrum of control (e.g., 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 2 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.