Leaf Spots (Helminthosporium, Cochliobolus, Cercospora)

Symptoms and the appearance of lesions can vary widely by pathogen and corn cultivar. Lesions will appear on leaves, leaf sheaths, and husks. Plant resistant varieties. Improve air circulation by increasing plant spacing and choosing sites with good airflow. Plow under crop debris promptly after harvest to speed decomposition. 

FRAC Group 3: 

• propiconazole (Tilt): 2 to 4 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 24h.
• pyraclostrobin + metconazole (Headline AMP, aka BAS 556 SC): 8 to 10 fl oz/A; PHI 7 to 20d, REI 12h, Groups 11 & 3.
• trifloxystrobin + propiconazole (Stratego): 10 to 12 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3. 

FRAC Group 7: 

• fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.

FRAC Group 11:

• azoxystrobin (Quadris F, aka Abound F): 6 to 15.5 fl oz/A; PHI 7d, REI 4h. 
• azoxystrobin + propiconazole (Quilt Xcel): 10.5 to 14 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.
•  fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.
• pyraclostrobin (Headline): 6 to 12 fl oz/A; PHI 7d, REI 12h. Apply in sufficient water to ensure thorough coverage. 
• pyraclostrobin + metconazole (Headline AMP, aka BAS 556 SC): 8 to 10 fl oz/A; PHI 7 to 20d, REI 12h, Groups 11 & 3.
• trifloxystrobin + propiconazole (Stratego): 10 to 12 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3. 

FRAC Group M03:

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

FRAC Group M05:

• chlorothalonil (Bravo Weather Stik, aka Bravo 720): 0.75 to 2 pt/A; PHI 14d, REI 12h. Fresh-market sweet corn only. See label for livestock restrictions.

Northern Corn Leaf Blight (Exserohilum [Helminthosporium] turcicum)

Northern corn leaf blight is an emerging problem on farms up and down the Connecticut River Valley. Symptoms begin as long, narrow, tan lesions that run parallel to leaf veins. Lesions coalesce and affect larger areas, and may cause a complete blighting of leaves. E. turcicum overwinters in and on leaf debris and conidia (spores) can be carried 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; a 1-year rotation is suggested for conventional practices and a 2-year rotation 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. 

FRAC Group 3:

• azoxystrobin + propiconazole (Quilt): 10.5 to 14 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.
• propiconazole (Tilt): 2 to 4 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 24h, Group 3.
• trifloxystrobin + propiconazole (Stratego): 10 to 12 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 &3.
• pyraclostrobin + metconazole (Headline AMP): 10 to 14.4 fl oz/A; PHI 7 to 20d, REI 12h, Groups 11 & 3.

FRAC Group 7:

• fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.

FRAC Group 11:

• azoxystrobin (Quadris F, aka Abound F): 6 to 15.5 fl oz/A; PHI 7d, REI 4h.
• azoxystrobin + propiconazole (Quilt): 10.5 to 14 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.
• pyraclostrobin (Headline): 6 to 12 fl oz/A; PHI 7d, REI 12h.
• trifloxystrobin + propiconazole (Stratego): 10 to 12 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 &3.
• pyraclostrobin + metconazole (Headline AMP): 10 to 14.4 fl oz/A; PHI 7 to 20d, REI 12h, Groups 11 & 3.

FRAC Group M03):

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

FRAC Group M05: 

• chlorothalonil (Bravo Weather Stik aka Bravo 720): 0.75 to 2 pt/A; PHI 14d, REI 12h. Fresh-market sweet corn only. See label for livestock restrictions.

Rust (Puccinia spp.)

The common rust fungus that occurs on sweet corn does not overwinter in the northeastern United States; each year it travels here on southerly winds. Rust appears as blister-like pustules called uredinia on the leaf epidermis. Uredinia produce abundant reddish-brown spores, hence the name “rust.” The disease 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. 

FRAC Group 3:

• azoxystrobin + propiconazole (Quilt): 10.5 to 14 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.
• propiconazole (Tilt): 4 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 24h. 
• pyraclostrobin + metconazole (Headline AMP): 10 to 14.4 fl oz/A; PHI 7 to 20d, REI 12h, Groups 11 & 3.
• trifloxystrobin + propiconazole (Stratego): 10 to 12 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.

FRAC Group 7:

• benzovindiflupyr (Aprovia): 4 to 10.5 fl oz/A; PHI 7d, REI 12h. Do not exceed 2 applications per year.

• fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.

FRAC Group 11:

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

• fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d sweet corn, 21d popcorn, REI 12h, Groups 7 & 11.

• pyraclostrobin (Headline): 6 to 12 fl oz/A; PHI 7d, REI 12h.
• pyraclostrobin + metconazole (Headline AMP): 10 to 14.4 fl oz/A; PHI 7 to 20d, REI 12h, Groups 11 & 3.
• trifloxystrobin + propiconazole (Stratego): 10 to 12 fl oz/A; PHI 14d sweet corn, 30d popcorn, REI 12h, Groups 11 & 3.

FRAC Group M03:

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

FRAC Group M05: 

chlorothalonil (Bravo Weather Stik, aka Bravo 720): 0.75 to 2 pt/A; PHI 14d, REI 12h. Fresh-market sweet corn only.

Seed Decay

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

Common Smut (Ustilago maydis)

Smut occurs sporadically, and typically less than 2% of the plants are affected. The disease is favored by dry conditions when temperatures are 80°F–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 silver-gray galls on the ears or stalks. When mature, the galls produce abundant black spores. Fungicides will not provide effective control of common smut. Remove and dispose of infected stalks. Plant resistant varieties. Avoid injuring plants during cultivation. Rotate away from corn for at least three years

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

Fungal stalk rots are serious diseases of corn, though their occurrence and severity vary from year to year. Symptoms often begin with wilting, followed by leaf discoloration, browning of the lower stalk, and development of a hollow pith. Crop losses due to difficulties with mechanical harvesting, ear rot caused by contact of ears with the soil, and premature plant death can occur. Factors that influence stalk rot incidence and severity include varietal susceptibility, weather conditions, the presence of foliar diseases, plant density, insect damage, moisture availability, soil fertility, and tillage practices. The disease is more severe and more common where nitrogen levels are high: a balanced and continuous supply of N reduces the occurrence of stalk rot. Adequate K reduces disease severity by strengthening cell walls. Practice proper spacing of plants and rows. Grow resistant hybrids. Manage insect pests and weeds.

Stewart's Wilt (Pantoea [Erwinia] stewartii)

This bacterial disease is spread by the corn flea beetle and is particularly damaging when susceptible varieties are planted following mild winters. Symptoms include narrow lesions, 5 cm or greater, with wavy margins. 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 frigid 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 severe infections with less yield loss. Resistance restricts the movement of the bacteria in the plant. 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 early and frequently for flea beetles as rapid growth of leaf tissue makes thorough insecticide coverage difficult.

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 corn and possibly other 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 where many weed hosts occur. Early symptoms are chlorotic spots and streaks; leaves will later develop a mosaic pattern. Plant resistant or tolerant corn varieties; see the Sweet Corn section for resistant varieties. 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, which can vector the virus. Johnson grass is an important perennial weed host for MDMV in southern New England and it should be eradicated.

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 corn earworm) 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.

IRAC Group 1:

• carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d, REI 24h, 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. Fall armyworm only.
• methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties.

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H.
• beta-cyfluthrin (Baythroid* XL): 2.8 oz/A; PHI 0d, REI 12h, Bee: H. For 1st and 2nd instars only.
• deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H. Apply to early instar larvae prior to boring into ear or stalk. See resistance statement on label. 
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H. Target 1st and 2nd instar only for fall armyworm. 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 48h, Bee: H. Use higher rate for large larvae.
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H. Use high rate for large larvae.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28. Use higher rate for large larvae. 
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H.
• zeta-cypermethrin (Mustang* Maxx): 2.8 to 4 oz/A; PHI 3d, REI 12h, Bee: H.

IRAC Group 5:

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

IRAC Group 11:

• Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L. Must be ingested. Use alone to control light populations or 1st and 2nd instar larvae. Add a contact insecticide to control more mature larvae and higher populations. For resistance management, may be rotated with Bt kurstaki products (e.g. Dipel).
• Bacillus thuringiensis kurstaki (Dipel DF^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L. Must be ingested. For resistance management, may be rotated with Bt aizawai (e.g. XenTari).

IRAC Group 22:

• indoxacarb (Avaunt): 2.5 to 3.5 oz/A; PHI 3d, REI 12h for mechanically harvested, 14 days for hand-harvested, Bee: H. For application through tassel push only.

IRAC Group 28:

• chlorantraniliprole (Coragen): 3.5 to 7.5 oz/A; PHI 1d, REI 4h, Bee: L. For foliar and overhead chemigation only.
• chlorantraniliprole + lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A. Use higher rate for large larvae. 

IRAC Group UN:

• Burkholderia spp. strain A396 (Venerate XC^OG): 1 to 4 qt/A; PHI 0d, REI 4h, Bee: M.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M.

Brown Marmorated Stink Bug (Halyomorpha halys)

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

IRAC Group 1:

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

IRAC Group 3:

• bifenthrin (Brigade* 2EC): 2.1 to 6.4 oz/A; PHI 1d, REI 12h, Bee: H. Do not make aerial or ground applications to corn if heavy rainfall is imminent.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28.

IRAC Group 4:

• acetamiprid (Assail 30SG): 5.3 oz./A; PHI 7d, REI 12h, Bee: M, Group 4A. Suppression only.

IRAC Group 28:

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

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 85ºF 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 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.

IRAC Group 1:

• carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d, REI 24h, 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.
• methomyl (Lannate* SP): 0.25 to 0.5 lb/A as ovicide/larvicide, 0.33 to 0.5 lb/A for whorl as needed; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties.

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H.
• beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H.
• deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H. Apply to early instar larvae prior to boring into ear or stalk. See resistance statement on label. 
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H. 
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28.
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H.
• zeta-cypermethrin (Mustang* Maxx): 2.8 to 4 oz/A; PHI 3d, REI 12h, Bee: H.

IRAC Group 5:

• spinetoram (Radiant SC): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M. Apply as broadcast or directed spray into ear zone.
• spinetoram + methoxyfenozide (Intrepid Edge): 8 to 12 oz/A; PHI 3d, REI 4h, Bee: M, Groups 5 & 18. Apply as broadcast or direct spray to ear zone. 
• spinosad (Entrust SC^OG): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M. Apply as directed spray to ear zone or as broadcast spray. Use sufficient spray volume and nozzle pressure to ensure thorough wetting of the silks.

IRAC Group 11:

• Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L. Must be ingested. Use alone to control light populations and add a contact insecticide to control moderate to heavy populations. Maintain frequent spray intervals.

IRAC Group 18:

• methoxyfenozide + spinetoram (Intrepid Edge): 8 to 12 oz/A; PHI 3d, REI 4h, Bee: M, Groups 18 & 5. Apply as broadcast or direct spray to ear zone. 

IRAC Group 28:

• chlorantraniliprole (Coragen): 3.5 to 7.5 oz/A; PHI 1d, REI 4h, Bee: L. For foliar and overhead chemigation only.
• chlorantraniliprole + lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

IRAC Group UN:

• Burkholderia spp. strain A396 (Venerate XC^OG): 1 to 4 qt/A; PHI 0d, REI 4h, Bee: M.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M.
• nuclear polyhedrosis virus of Helicoverpa zea (Gemstar^OG): 4 to 10 oz/A; PHI 0d, REI 4h, Bee: L. Highly selective for corn earworm larvae. Must be ingested. Make applications from early vegetative growth to tasseling and before emergence of silks. Retreatment may be required at 2- to 3-day intervals depending on egg counts and crop growth rate due to short residual activity of the virus.
• soybean oil (Golden Pest Spray Oil^OG): 2 gal/A; PHI 0d, REI 4h, Bee: L. Low-volume application. Apply when insects first appear. Repeat weekly for additional control.

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.

IRAC Group 1:

• methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties.

IRAC Group 3:

• alpha-cypermethrin (Fastac CS*): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H. Aphid control may be variable depending on species present and host-plant relationships.
• deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H. Suppression only.
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H. For optimum results, direct spray at the aphid population to achieve maximum coverage of the exposed insects. 
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H. See resistance statement on label. Suppression only.
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H. See resistance statement on label. Suppression only.

IRAC Group 4:

• acetamiprid (Assail 30SG): 2.1 to 2.9 oz./A; PHI 1d, REI 12h, Bee: M, Group 4A.
• flupyradifurone (Sivanto): 7 to 14 oz/A; PHI 7d, REI 4h, Bee: L, Group 4D. Foliar application.
• thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. For early season protection from corn leaf aphid.

IRAC Group UN:

• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M.
• mineral oil (SuffOil-X^OG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L. Apply as needed.

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.

IRAC Group 1:

• carbaryl (10% Sevin Granules): 20 lb/A; PHI 2d, REI 12h, 21 days for workers detasseling corn, Bee: H, Group 1A. Ground broadcast equipment applications only. Hand-harvesting prohibited.
• 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.
• methomyl (Lannate* SP): 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties. Variegated cutworm only.
• tebuprimphos + beta-cyfluthrin (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 1B & 3A. Apply at planting as band or in-furrow. Must be incorporated at least 1" into soil. VT only. 

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H.
• beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H.
• beta-cyfluthrin + tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A & 1B. Apply at planting as band or in-furrow. Must be incorporated at least 1" into soil. VT only.
• bifenthrin (Capture* LFR): 3.4 to 17 oz/A at planting, 4 to 5.3 oz/A pre-plant incorporated (PPI), 3.4 oz/A pre-emergence, 2.8 to 8.5 oz/A foliar; PHI 1d, REI 12h, Bee: H. For PPI applications, do not incorporate deeper than 3 inches. Black cutworm only for PPI and pre-emergence applications.
• bifenthrin + Bacillus amyloliquefaciens strain D747 (Ethos XB): 3.4 to 17 oz/A at planting, 4.5 to 5 oz/A pre-plant incorporated (PPI), 3.4 oz/A pre-emergence, 2.8 to 8.5 oz/A foliar; PHI 1d, REI 12h, Bee: H, IRAC Group 3A & FRAC Group BM02. Pre-mix of insecticide and biofungicide that suppresses pathogens responsible for damping off. Black cutworm only for PPI and pre-emergence applications.
• deltamethrin (Delta Gold*): 1 to 1.5 oz/A; PHI 1d, REI 12h, Bee: H. 
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A foliar; 0.10 to 0.18 oz/1000 row ft at-planting as T-band or band only for all New England states except NH; 0.26 oz/1000 row ft permitted at-planting in NH only; PHI 1d foliar, 21d soil, REI 48h, Bee: H.
• lambda-cyhalothrin (Warrior* II): 0.33 oz/1000 row ft at planting (T-band or in-furrow), 1.28 to 1.92 oz/A foliar; PHI 1d foliar, 21d soil, REI 24h, Bee: H.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28.
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H.
• tefluthrin (Force* CS): 0.46 to 0.57 oz/1000 row ft, 0.34 to 0.46 oz/1000 row ft if cutworm is only pest present; REI 48h, Bee: H. For T-banded or in-furrow applications at planting.
• zeta-cypermethrin (Mustang* Maxx): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H.

IRAC Group 4:

• thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. For early-season protection from black cutworm.

IRAC Group 5: 

• spinosad (Seduce^OG): 20 to 44 lb/A, 0.5 to1 lb/1000 sq ft.; PHI 1d, REI 4h, Bee: M. Spread bait on soil around plants. 

IRAC Group 28:

• chlorantraniliprole + lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 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 5–7 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"–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.

IRAC Group 1:

• carbaryl (Sevin XLR Plus): 1.5 to 2 qt/A; PHI 2d, REI 24h, 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.
• methomyl (Lannate* SP): 0.25 to 0.5 lb/A on ears 1–3 days or as needed; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties. 

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.8 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H.
• beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H. Applications must be made prior to larva boring into the plant.
• deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H. Apply to early instar larvae prior to boring into ear or stalk. See resistance statement on label. 
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H.
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H. 
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28.
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H.
• zeta-cypermethrin (Mustang* Maxx): 2.8 to 4 oz/A; PHI 3d, REI 12h, Bee: H.

IRAC Group 5:

• spinetoram (Radiant SC): 3 to 6 oz/A; PHI 1d, REI 4h, Bee: M. Apply as directed spray into leaf whorls or as broadcast spray.
• spinetoram + methoxyfenozide (Intrepid Edge): 4 to 12 oz/A; PHI 3d, REI 4h, Bee: M, Groups 5 & 18. Apply as broadcast or direct spray to ear zone. 
• spinosad (Entrust SC^OG): 1.5 to 6 oz/A; PHI 1d, REI 4h, Bee: M. Apply as directed spray into leaf whorls or as broadcast spray. 

IRAC Group 11:

• Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L. Must be ingested. 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. Must be ingested. For resistance management, may be rotated with Bt aizawai products.

IRAC Group 18:

• methoxyfenozide (Intrepid 2F): 4 to 16 oz/A; PHI 3d, REI 4h, Bee: L 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 oz./A; PHI 3d, REI 4h, Bee: M, Groups 18 & 5. Direct application at the whorl for early-season infestations.

IRAC Group 22:

• indoxacarb (Avaunt): 2.5 to 3.5 oz/A; PHI 3d, REI 12h for mechanically harvested, 14 days for hand harvested, Bee: H. For application through tassel push only.

IRAC Group 28:

• chlorantraniliprole (Coragen): 3.5 to 7.5 oz/A; PHI 1d, REI 4h, Bee: L. For foliar and overhead chemigation only.
• chlorantraniliprole + lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 3A.

IRAC Group UN:

• Burkholderia spp. strain A396 (Venerate XC^OG): 1 to 4 qt/A; PHI 0d, REI 4h, Bee: M.
• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M.

Flea Beetle, Corn (Chaetocnema pulicaria)

Corn flea beetles are black, tinged with bronze or bluish-green, and overwinter in plant residue around 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 90ºF–100ºF, 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.

IRAC Group 1:

• carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d, REI 24h, 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.
• methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties.
• phorate (Thimet* 20-G): 4.5 to 6 oz/1000 row ft for any row spacing; PHI 30d, REI 48h, Bee: H, Group 1B. At planting treatment. Granules must be incorporated into the soil. DO NOT use in-furrow or apply more than once per season.
• terbufos (Counter* 20G): 4.5 to 6 oz/1000 row ft for any row spacing; REI 48h, Bee: M, Group 1B. For banded or in-furrow applications. 

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H.
• beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H.
• deltamethrin (Delta Gold*): 1 to 1.5 oz/A; PHI 1d, REI 12h, Bee: H.
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H.
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28.
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H.
• zeta-cypermethrin (Mustang* Maxx): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H.

IRAC Group 4:

• acetamiprid (Assail 30SG): 4 to 5.3 oz./A; PHI 7d, REI 12h, Bee: M, Group 4A.
• thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. For early-season protection from corn flea beetles.

IRAC Group 28:

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

Japanese Beetle (Popillia japonica)

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

IRAC Group 1:

• carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d, REI 24h, 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.

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H. Adults only.
• beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H. Adults only.
• deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H. Adults only.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H. Adults only.
• lamba-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H. Adults only.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28. Adults only. 
• pyrethrin (PyGanic EC5.0^OG): 4.5 to 15.61 oz/A, or 0.25 to 0.50 oz/gal and 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M.
• zeta-cypermethrin (Mustang* Maxx): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H. Adults only.

IRAC Group 4:

• acetamiprid (Assail 30SG): 5.3 oz./A; PHI 7d, REI 12h, Bee: M, Group 4A.

IRAC Group 28:

• chlorantraniliprole + lambda-cyhalothrin (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 28 & 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 (four-spotted 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 supersweet and Bt varieties, are more susceptible to infestation. Research has shown that the tip cover's length and tightness are important to reduce infestations. To prevent or reduce damage, select varieties with good, tight 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, lambda-cyhalothrin, bifenthrin, and methomyl 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.

IRAC Group 1:

• carbaryl (Sevin XLR Plus): 1 to 2 qt/A; PHI 2d, REI 24h, 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.
• malathion (Malathion 57 EC): 1.5 pt/A; PHI 5d, REI 12h, 72h for workers detasseling corn, Bee: H, Group 1B. Begin treatment when 10% of ears show silk. 
• methomyl (Lannate* SP): 0.25 to 0.5 lb/A; PHI 0d, REI 48h, Bee: H, Group 1A. May cause injury in some varieties.

IRAC Group 3:

• alpha-cypermethrin (Fastac* CS): 2.2 to 3.8 oz/A; PHI 3d, REI 12h, Bee: H. Adults only.
• bifenthrin (Capture* LFR): 2.8 to 8.5 fl oz/A; PHI 1d, REI 12h, Bee: H. Foliar application only. 
• esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 1d, REI 12h, Bee: H. Adults only.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H. Adults only.
• lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 1d, REI 24h, Bee: H. Adults only.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28. Adults only. 
• zeta-cypermethrin (Mustang* Maxx): 2.24 to 4 oz/A; PHI 3d, REI 12h, Bee: H. Adults only.

IRAC Group 4: 

• acetamiprid (Assail 30SG): 4 to 5.3 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A. Dusky sap beetle only.

IRAC Group 28:

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

Seedcorn Maggot (Delia platura)

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

IRAC Group 1:

• phorate (Thimet* 20-G): 4.5 to 6 oz/1000 row ft for any row spacing; PHI 30d, REI 48h, Bee: H, Group 1B. At-planting treatment. Granules must be incorporated into the soil. DO NOT use in-furrow or apply more than once per season.
• tebuprimphos + beta-cyfluthrin (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 1B & 3A. Apply at planting as band or in-furrow. Must be incorporated at least 1" into soil. VT only. 
• terbufos (Counter* 20G): 4.5 to 6 oz/1,000 row ft (banded or in-furrow); REI 48h, Bee: M, Group 1B.

IRAC Group 3:

• beta-cyfluthrin + tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A & 1B. Apply at planting as band or in-furrow. Must be incorporated at least 1" into soil. VT only.
• bifenthrin (Capture* LFR): 3.4 to 17 oz/A at-planting; 4 to 5.3 oz/A pre-plant incorporated (PPI); PHI 1d, REI 12h, Bee: H. For PPI, do not incorporate deeper than 3 inches.
• gamma-cyhalothrin (Declare*): 0.10 to 0.18 oz/1000 row ft at-planting; 0.26 oz/1000 row ft permitted at-planting in NH only; PHI 21d, REI 48h, Bee: H.
• lambda-cyhalothrin (Warrior* II): 0.33 oz/1000 row ft at planting (T-band or in-furrow); REI 24h, Bee: H,.
• tefluthrin (Force* CS): 0.46 to 0.57 oz/1000 row ft; REI 48h, Bee: H. For T-band or in-furrow applications at planting.

IRAC Group 4:

• thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. 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.

IRAC Group 3:

• beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H. Application must be made prior to larva boring into the plant.
• deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H. 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.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H. 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.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28. 
• permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 1d, REI 12h, Bee: H.

IRAC Group 28:

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

IRAC Group UN:

• Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M.

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. 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.

IRAC Group 3:

• beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H.
• gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 1d, REI 48h, Bee: H.
• lambda-cyhalothrin + chlorantraniliprole (Besiege*): 6 to 10 oz/A; PHI 1d, REI 24h, Bee: H, Groups 3A & 28. 

IRAC Group 5:

• spinetoram + methoxyfenozide (Intrepid Edge): 4 to 12 oz/A; PHI 3d, REI 4h, Bee: M, Groups 5 & 18. Apply as broadcast or direct spray to ear zone. 

IRAC Group 18:

• methoxyfenozide (Intrepid 2F): 4 to 16 oz/A; PHI 3d, REI 4h, Bee: L, Group 18. Apply at first sign of feeding damage.
• methoxyfenozide + spinetoram (Intrepid Edge): 4 to 12 oz/A; PHI 3d, REI 4h, Bee: M, Groups 18 & 5. Apply at first sign of feeding damage. 

IRAC Group 28:

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

IRAC Group UN:

• Burkholderia spp. Strain A396 cells and spent fermentation media (Venerate XC^OG): 1 to 4 qt/A; PHI 1d, REI 12h, Bee: H.

Wireworms and White Grub

See the Potato insect control section for more information on wireworms. 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 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.

IRAC Group 1:

• ethoprop (Mocap* 15%G): 8 oz/1000 row ft; 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. Extremely toxic to birds. Do not leave granules on soil surface and do not use more than once per season. Suppression only for white grubs.
• phorate (Thimet* 20-G): 4.5 to 6 oz/1000 row ft. for any row spacing; PHI 30d, REI 48h, Bee: H, Group 1B. At-planting treatment. Granules must be incorporated into the soil. Do not use in-furrow or apply more than once per season.
• tebuprimphos + beta-cyfluthrin (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 1B & 3A. Apply at planting as band or in-furrow. Must be incorporated at least 1" into soil. VT only.
• terbufos (Counter* 20G): 4.5 to 6 oz/1000 row ft. banded or in-furrow; REI 48h, Bee: M, Group 1B. 

IRAC Group 3:

• beta-cyfluthrin + tebuprimphos (Aztec* 2.1G): 6.7 oz/1000 row ft; REI 48h, Bee: H, Groups 3A & 1B. Apply at planting as band or in-furrow. Must be incorporated at least 1" into soil. VT only.
• bifenthrin (Capture* LFR): 3.4 to 17 oz/A at planting, 4 to 5.3 oz/A pre-plant incorporated (PPI); PHI 1d, REI 12h, Bee: H For PPI, do not incorporate deeper than 3". 
• gamma-cyhalothrin (Declare*): 0.041 to 0.82 oz/1000 row ft at planting, 0.26 oz/1000 row ft permitted at planting in NH only; REI 48h, Bee: H. Suppression only for wireworms. For reducing white grub damage only when used as T-band or in-furrow on light to moderate infestations in CT, MA, ME, RI, and VT. 
• lambda-cyhalothrin (Warrior* II): 0.33 oz/1000 row ft. at planting (T-band or in-furrow); REI 24h, Bee: H.
• tefluthrin (Force* CS): 0.46 to 0.57 oz/1000 row ft.; REI 48h, Bee: H. For T-banded or in-furrow applications at planting. Use high rate for heavy infestations. For best control, apply as in-furrow.

IRAC Group 4:

• thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. 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).

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 which time all fields of sweet corn planted up to that 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/A 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 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

The following herbicides are nonselective and are used to control weeds that are present in a field prior to planting or before the crop emerges, which is especially useful for the Stale Seedbed Technique (see the Weed Management section for more information). These herbicides are also used to kill the cover crop in a minimum- or no-till system.

• glyphosate (Roundup Power Max): PHI 7d, REI 4h, Group 9.
• pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.
• paraquat (Gramoxone SL 2.0*): REI 48h, Group 22. *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.

Preemergent Herbicides (before weeds germinate)

HRAC Group 3:

• pendimethalin (Prowl H2O): 2 to 4 pt/A; REI 24h. Apply after planting corn seed at least 1.5" deep, 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. Do not use in minimum- or no-till systems.

HRAC Group 5:

• simazine (Princep 4L): Up to 2 qt/A; PHI 45d sweet corn, 60d popcorn, REI 12h. 1 application per year. Apply preplant incorporated or to the soil surface immediately after planting before corn emerges. Does not control annual grasses. Do not apply on highly erodible soils unless there is at least 30% plant residue cover.

HRAC Group 14:

• saflufenacil (Sharpen): 2 fl oz/A; REI 12h. Sweet corn for processing only and popcorn. Do not exceed 6 fl oz/A per year. Apply preplant incorporated up to 14 days before planting, or immediately after planting before corn emerges. 

HRAC Group 15:

• acetochlor (Surpass EC): 1.5 to 3.75 pt/A; REI 12h. Do not exceed 3.57 pt/A per year. Do not apply to sandy soils or within 50’ of any well where the depth to groundwater is 30’ or less. Apply as close as possible to planting or after planting and incorporate 0.25” into the soil with water or cultivation. If applied more than 14 days before planting, incorporate 2” into the soil. Do not apply after sweet corn has emerged. Delay cultivation as long as possible after applying.
• dimethenamid (Outlook): 8 to 24 fl oz/A; PHI 50d, REI 12h. Do not exceed 24 fl oz/A per year. Can be split-applied. Apply up to 45 days before planting and until corn is 12” tall or at layby for popcorn.
• pyroxasulfone (Zidua): 1 to 4 fl oz/; PHI 37d, REI 12h. Do not exceed 2.75 to 5 fl oz/A per year. Apply after planting until the V4 stage, to corn planted at least 1" into the soil.
• s-metolachlor (Dual Magnum): 1.33 to 2.6 pt/A; PHI 30d, REI 24h. Do not exceed 3.9 pt/A per year. Make beds before applying if planting into beds. Apply before planting until corn is 40” tall. When corn is more than 5” tall, direct spray towards the base of plants.

Pre- and Postemergent Herbicides

HRAC Group 2:

• halosulfuron-methyl (Sandea): 0.67 to 1 oz/A; PHI 30d, REI 12h. Do not exceed 2 oz/A per year. Apply over the top of corn, or with drop nozzles from the spike through layby stage. If making sequential applications, the second application should be applied only with directed drop nozzles to avoid application into the corn plant whorl. Do not use on “Jubilee” sweet corn.

HRAC Group 5:

• atrazine (Aatrex 4L): 2.4 to 4 pt/A; REI 12h. It is recommended to only use 2 pt/A in Massachusetts. Do not exceed 5 pt/A per year. Apply before planting until corn is 12” high, as the primary broadleaf herbicide treatment instead of an application at planting, or as an emergency treatment if the soil-applied broadleaf herbicide treatment fails. On highly erodible soils with less than 30% residue cover at planting, use a maximum of 3.2 pt/A. 

HRAC Group 27:

• mesotrione (Callisto): 3 to 7.7 fl oz/A; PHI 45d, REI 12h. Do not exceed 7.7 fl oz/A per application. Can make 1 application before corn emergence and 1 after emergence, or 2 applications after corn emergence when corn is less than 30” tall or at the 8-leaf stage. Applying after crop emergence may cause crop bleaching in some sweet corn varieties, but should not affect yield. Adjuvant restrictions apply to sweet corn applications. Do not apply to white popcorn varieties. Severe corn injury resulting in yield loss may occur if any organophosphate or carbamate insecticide is applied foliar postemergence within 7 days before or after Callisto application.

Postemergent Herbicides (after weeds germinate)

HRAC Group 0:

• pelargonic acid (Scythe): 3 to 10% solution; PHI 1d, REI 12h. Apply preplant, as a directed and shielded spray during crop growth, or before emergence. Contact with crop will cause damage.

HRAC Group 1:

• sethoxydim (Poast): 1.5 pt/A; PHI 30d, REI 12h. Use only with Poast Protected corn hybrids. Do not exceed 3 pt/A per year. Apply to actively growing grasses, until the onset of pollen shed. Do not apply after pollination. BASF has stopped production and will discontinue the registration at the end of 2027.

HRAC Group 2:

• nicosulfuron (Accent Q): 0.45 to 1.8 oz/A; PHI 30d, REI 4h. Not for use in NH. 1 application per year. Apply broadcast before corn is 12” tall to actively growing grasses. If corn is 12"–18" tall, apply with drop nozzles. Do not apply if corn is greater than 18". Do not apply to white popcorn varieties. Check label for specific precautions related to previous insecticide applications. Do not use if the crop exhibits herbicide injury from previous applications. 

HRAC Group 4:

• 2,4-D (Amine 4): 1 to 2 pt/A; PHI 45d sweet corn, 7d popcorn, REI 48h. Do not exceed 3.15 pt/A per year. Apply once 7–14 days before planting or after planting but before corn emergence, and once after corn emergence when corn is less than 8” tall or with drop nozzles if greater than 8” tall through the dough/denting stage. Do not use on sandy soil. Can apply to popcorn in the dough stage. Do not cultivate for at least 7–10 days after application to corn that has emerged or stem breakage may occur. Use only the amine formulation of 2,4-D and avoid spray drift to desirable broadleaf crops.
• clopyralid (Stinger): 0.33 to 0.67 pt/A. PHI 30d, REI 12h. Do not exceed 0.67 pt/A per year. Apply to actively growing weeds. Apply from corn emergence until it is 18” (sweet corn) or 24” (popcorn) tall. To target Canada thistle, apply when the majority of thistle plants have emerged (rosette to 8") and do not cultivate for 14–20 days before or after application.
• clopyralid (Clean Slate): 0.33 to 0.67 pt/A; PHI 30d, REI 12h. Do not exceed 0.67 pt/A per year. Apply to actively growing weeds. Apply from corn emergence until it is 18” (sweet corn) or 24” (popcorn) tall. To target Canada thistle, apply when the majority of thistle plants have emerged (rosette to 8") and do not cultivate for 14–20 days before or after application.

HRAC Group 5:

• ametryn (Evik DF): 2 lb/A; REI 12h. Popcorn only. 1 application per year. Apply as a directed spray to the weeds after the shortest corn is at least 12” tall.

HRAC Group 6:

• bentazon (Basagran): 0.8 to 1.6 pt/A; REI 48h. Do not exceed 3.2 pt/A per year. Apply when corn has 1–5 leaves. An effective treatment in an emergency situation to control certain broadleaf weeds and fairly effective against 4- to 6”-tall yellow nutsedge. Spray drift injury risk is less than that of 2,4-D.

HRAC Group 9:

• glyphosate (Roundup Power Max): 15 fl oz to 3.1 qts/A; PHI 7d, REI 4h. Do not exceed 5 qt/A per year. Apply 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. Spray contact can cause plant death in non-Roundup Ready varieties. Spray additive recommendation varies with formulation–see label. To target quackgrass, apply after corn harvest to actively growing quackgrass 6"–8" tall. Wait at least 5 days after application before plowing. Most effective on bindweed and milkweed at or after bloom.

HRAC Group 14:

• carfentrazone (Aim EC): 0.5 to 1 fl oz/A; PHI 14 leaf collars, REI 12h. Do not exceed 2 fl oz/A per year. Apply as a pre-plant burndown up to 1 day after seeding until corn is at the 14 leaf-collar stage. Use drop nozzles with higher rates. Foliar speckling often occurs after application.
• fluthiacet-methyl (Cadet): 0.6 to 0.9 fl oz/A; PHI 40d, REI 12h. Sweet corn for processing only and popcorn. Do not exceed 1.25 fl oz/A per season. Apply as a preplant burndown or after corn emerges until corn is 48” tall or tasseling occurs. Do not cultivate within 2 days before or after applying. Do not apply to severely stressed or wet crop.

HRAC Group 22:

• paraquat (Gramoxone SL 3.0*): 0.7 to 1.3 pt/A; REI 48h. Do not exceed 8 pt/A per year. Apply in a banded over-row or broadcast application before corn emergence, or with a hooded or shielded sprayer after emergence. Can apply without a directed sprayer when corn is at least 10" tall and nozzles spray no higher than 1/3 of the corn stalk. Spray contact can cause crop death. 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.

HRAC Group 27:

• tembotrione (Laudis): 3 fl oz/A; REI 12h. 1 application per year for sweet corn, up to 2 applications per year for popcorn. Apply after corn emergence until the V7 (sweet corn) or V8 (popcorn) stage, or as a postharvest burndown. Do not use on “Merit” or “Shogun” sweet corn.
• tolpyralate (ShieldEx 400 SC): 1 to 1.35 fl oz/A; PHI 35d sweet corn, 45d popcorn, REI 12h. Do not exceed 2.7 fl oz/A per year. Apply when corn is emerged up to the V6 stage or 20” tall.
• topramezone (Impact): 0.75 to 2 fl oz/A. PHI 45d, REI 12h. Do not exceed 2 fl oz/A per year. Apply after corn has emerged up until the V8 stage. Crops under stress may show transient bleaching.

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.