| Corn, Sweet - Insect Control |
 |
 |
Page 8 of 9
Insect ControlNOTE: For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 20 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients. Sprayer Type and ConfigurationBest coverage is achieved by using a boom-type sprayer with drop nozzles. The nozzles should be arranged so that one nozzle is over the row, one nozzle is directed up toward the ear and one nozzle is directed down: hence, sandwiching the ear between the spray paths. TX-10 or D2-25 hollow-cone nozzles at 75 to 100 psi provide excellent coverage. Do not use flat-fan nozzles or nozzles that produce large droplets. For more information, see references #15, #19 in References For Commercial Vegetable Growers section.Mist blowers provide the poorest coverage, as it is not possible to concentrate the spray on the ear zone with this type of sprayer. If a mist blower is used, check to make sure ears are being covered by placing water-sensitive cards on ears across the rows and on ears on both sides of the plant. Check the cards for coverage after a test application of water. Remember that each row of corn acts as a filter, removing insecticide from air as it passes across each row European Corn Borer (ECB)European corn borer (ECB) is a resident pest that has two generations per year in southern and central New England and one generation in northern New England. Sweet corn is one of over 200 crop and weed host plants of this pest. 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. The moths are about 3/4” long, light brown in color with lighter bands on the wings. Three to seven 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 5-7 days (100 degree days, with a base temperature of 50°F).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 inch long and full-grown larvae are 3/4 to 1 inch 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. 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. Check with your state IPM program for specific timing and thresholds. ECB flight can be monitored with two Scentry Heliothis net traps baited with New York (E II) or Iowa Z (I) lures, placed at least 50 feet 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 two 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 five to twenty plants throughout the field. Treat if more than 15% of the plants have one or more larvae present. A sprayer configuration with one nozzle directed into the tassel and a single drop nozzle to the upper parts of the plant gives the best control. At high levels of infestation, two applications may be needed to provide control. Since the ECB overwinters as a mature larva in corn stalks and stubble, plowing under corn refuse in the fall or early spring will help control this pest. Fields that have been in sweet corn or field corn for a long time tend to have higher pressure from ECB. Corn grown under plastic matures sooner in the year, so developing ears may be present during the first flight of ECB. Because of this synchrony between developing ears and ECB egg laying, corn grown under plastic can be heavily infested by this pest. If plants are in silk and moths are active, protect developing ears. This is also true for late season corn, especially when other caterpillar pests are absent. Corn that has been genetically modified to produce the insect toxin found in Bacillus thuringiensis (Bt), e.g. “Attribute®” varieties, should have adequate defense against European corn borer and should not require additional insecticide applications for this insect. Natural enemies include the twelve spotted ladybeetle which preys on eggs and small larvae. Releases of Trichogramma ostriniae, which attacks ECB eggs, can reduce the need for insecticide applications. See Biological controls or References for more information. Use of selective products to control ECB will conserve natrual enemies of aphids and ECB Bacillus thuringiensis aizawai (XenTari): 0.5 to 1.5 lb/A (0 dh, REI 4h, Group 11). See the general recommendations for B.t. kurstaki below. OMRI listed. beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A (0 dh, REI 12h, Group 3A). deltamethrin (Decis* 1.5EC): 1.5 to 2.4 oz/A (1 dh, REI 12h, Group 3A). esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A (1 dh, REI 12h, Group 3A). flubendiamide (Belt SC): 2 to 3 oz/A (1 dh, REI 12h, Group 28). Must be injested; thorough coverage is needed. gamma-cyhalothrin (Proaxis*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). indoxacarb (Avaunt): 2.5 to 3.5 oz/A (3 dh, REI 12h for mechanically harvested and 14 days for hand harvested, Group 22). Whorl through tassel emergence (prior to silking) application only. lambda-cyhalothrin (Warrior*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). methomyl (Lannate SP*): 1/4 to 1/2 lb/A (0 dh for ears, 3 dh if used for feed or forage, REI 48h, Group 1A). Treat a small area of the field to determine cultivar sensitivity before spraying entire field. Phytotoxicity may occur on some varieties. More severe damage may occur with the Lannate* LV formulation than with the Lannate* SP (Soluble Powder) formulation. methoxyfenozide (Intrepid 2F): 4 to 8 oz/A (3 dh, REI 4h, Group 18). Insect growth regulator. Works on all instars. Feeding stops within hours but death takes several days. permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A (1 dh, REI 12h, Group 3A). spinetoram (Radiant SC): 3 to 6 oz/A (1 dh, REI 4h, Group 5). spinosad (Entrust): 0.5 to 2 dry oz/A (1 dh, REI 4h, Group 5). Do not feed ears/stalks to animals for 7 days. OMRI listed. thiodicarb (Larvin* 3.2): 20 to 30 oz/A (0 dh, REI 48h, Group 1A). zeta-cypermethrin (Mustang*): 3 to 4.3 oz/A (3 dh, REI 12h, Group 3A). Common and Fall ArmywormThe fall armyworm does not overwinter in New England. Infestations result from fertile moths carried northward on storm fronts from southern states from mid July into September. Flights are heavier near the coast, but move inland as well. The flights are sporadic and difficult to predict, and do not necessarily correspond with corn earworm flights, so monitoring with pheromone traps in whorl stage corn is very useful.Moths (males) have mottled brown forewings with a slanting white bar across the wing, and plain light tan hindwings. They measure about three quarters of an inch long. Female moths lay clusters of eggs on the leaves of a variety of host plants, preferring whorl stage corn to older corn. Eggs hatch in 2-10 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 1/2 inches. The head capsule is dark with a distinctive light colored marking in the form of an upside-down Y. (See photo identification section.) Feeding damage from caterpillars occurs first in whorl stage corn, deep within the whorl, on leaves and in the newly forming green tassel. Watch whorl stage corn for ragged feeding damage and masses of sawdust-like excrement. Fall armyworm larvae eat into the side of corn ears, leaving behind frass and a large hole. They also feed in the tip, making a mess of the kernels. The most effective way to prevent ear damage is to apply controls during whorl and pretassel stage. If flights are very high, silk sprays may be needed. Monitor fall armyworm moths with a bucket trap (e.g., Universal Moth Trap or Multipher traps) with a lure (Scentry lure, PSU type) clipped under the lid and a vapor strip placed inside the trap. Hang the trap on a stake at plant height in whorl stage corn. Count moths at least weekly. Replace lure every two weeks. Replace vapor strip every 4-6 weeks. Scout whorl and pretassel 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 start at random, not only where you can see damage. A plant is infested if at least one caterpillar is found. If feeding damage is old and no larva is found, the caterpillar may have left the plant to pupate in the soil. If 15% or more of plants are infested with FAW, a control is needed. In emerging tassels, combine counts for ECB and FAW. For example, if 10% of plants have FAW and 12% have ECB, the combined infestation is 22%, above the 15% threshold. Common armyworm, also known as armyworm or true armyworm, migrates from southern areas anytime from March to September. Eggs are laid on grasses and grains in preference to corn and other crops. Larvae feed at night and are grayish green with a broad stripe on each side and a yellow-brown head. Damage is similar to fall armyworm and is usually sporadic and not sufficient to require treatment. Outbreaks are not common in New England but may occur and cause significant damage. Bacillus thuringiensis aizawai (XenTari): 0.5 to 2 lb/A (0 dh, REI 4h, Group 11). Use alone to control light populations of first and second instar larvae. Add a contact insecticide to control more mature larvae and higher populations. OMRI listed. Bacillus thuringiensis kurstaki (Dipel DF): 0.5 to 1 lb/A (0 dh, REI 4h, Group 11). Use alone to control light populations of first and second instar larvae. Use higher rates. Can be tank mixed with other insecticides to control more mature larvae and higher populations. OMRI listed. beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A (0 dh, REI 12h, Group 3A). For first and second instar only. flubendiamide (Belt SC): 2 to 3 oz/A (1 dh, REI 12h, Group 28). Must be injested; thorough coverage is needed. gamma-cyhalothrin (Proaxis*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). For control of first and second instars only. lambda-cyhalothrin (Warrior*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). Use high rate for large larvae. spinetoram (Radiant SC): 3 to 6 oz/A (1 dh, REI 4h, Group 5). spinosad (Entrust): 0.5 to 2 dry oz/A (1 dh, REI 4h, Group 5). Do not feed ears/stalks to animals for 7 days. OMRI listed. Corn Earworm (CEW)Corn earworm (CEW) moths migrate annually into the Northeast, traveling north on storm fronts, and may arrive anytime from mid-July through September. Heaviest numbers are found in coastal areas and up the major river valleys. The severity of infestations varies from year to year and may change suddenly during the season. Spray Intervals for Corn Earworm
See Reference 17 for more information on organic controls for corn earworm. Bacillus thuringiensis aizawai (XenTari): 0.5 to 2 lb/A (0 dh, REI 4h, Group 11). Use alone to control light populations and add a contact insecticide to control moderate to heavy populations. OMRI listed. beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A (0 dh, REI 12h, Group 3A). deltamethrin (Decis* 1.5EC): 1.5 to 2.4 oz/A (1 dh, REI 12h, Group 3A).esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A (1 dh, REI 12h, Group 3A). flubendiamide (Belt SC): 2 to 3 oz/A (1 dh, REI 12h, Group 28). Must be injested; thorough coverage is needed. gamma-cyhalothrin (Proaxis*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). lambda-cyhalothrin (Warrior*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). methomyl (Lannate SP*): 1/4 to 1/2 lb/A (0 dh for ears, 3 dh if used for feed or forage, REI 48h, Group A). Some corn varieties may be damaged by methomyl. More severe damage may occur with the Lannate* LV formulation than with the Lannate* SP (Soluble Powder) formulation. May not provide effective control under high corn earworm pressure. permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A (1 dh, REI 12h, Group 3A). soybean oil (Golden Pest Spray Oil): 0.5 ml applied by hand directly to silk within 6-7 days after 50% of the ears are silking (REI 4h, 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. OMRI listed. spinetoram (Radiant SC): 3 to 6 oz/A (1 dh, REI 4h, Group 5). Effective for low to moderate CEW pressure. Switch to another product when CEW pressure is high (13 or more moths/night in pheromone trap) or when a 3-day spray schedule is warranted. spinosad (Entrust): 1 to 2 dry oz/A (1 dh, REI 4h, Group 5). Do not feed ears/stalks to animals for 7 days. Effective for low to moderate CEW pressure. Less effective when CEW pressure is high (13 or more moths/night in pheromone trap) or when a 3-day spray schedule is warranted. OMRI listed. thiodicarb (Larvin* 3.2): 20 to 30 oz/A (0 dh, REI 48h, Group 1A). zeta-cypermethrin (Mustang*): 3 to 4.3 oz/A (3 dh, REI 12h, Group 3A). Corn Leaf AphidThe corn leaf aphid (CLA) is blue-green or black, with black legs. These aphids overwinter as females on grass weeds and cereals, particularly barley. Females produce live young which mature in as little as 6 days. There are up to 9 generations per year. CLAs first colonize whorl leaves and the immature tassel. Populations may become numerous enough to interfere with pollen shed and to stunt plants. 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. The presence of high aphid populations or honey dew on corn ears can render the ears unmarketable. Honey dew on ears may increase the number of CEW moths attracted to the plants. Monitor for aphids while scouting pre-tassel stage corn for ECB or FAW in late July or August. Pre-tassel stage sprays may be needed in dry seasons when 50% of the plants are infested. Sweet corn plantings that are seeded before 10 June are not bothered by corn leaf aphids. Varieties with purple or green tassels seem to be less susceptible to aphid build-up than those with yellow tassels. Ample rainfall or irrigation during the silk stage can reduce or eliminate aphid damage. Natural enemies reduce aphid numbers, but may not provide adequate control, especially in dry seasons. Whenever possible, conserve predators and parasites by using selective insecticides to control caterpillars before silkingdeltamethrin (Decis* 1.5EC): 1.5 to 2.4 oz/A (1 dh, REI 12h, Group 3A). Suppression only. endosulfan (Thionex* 50W ): 2 lb/A (1 dh, REI 24h, Group 2A). Use for fresh corn only, not on corn for processing or for livestock feed. esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A (1 dh, REI 12h, Group 3A). gamma-cyhalothrin (Proaxis*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). Suppression only. lambda-cyhalothrin (Warrior*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). Suppression only.methomyl (Lannate SP*): 1/4 to 1/2 lb/A (0 for ears, 3 dh if used for forage, REI 48h, Group 1A). See ECB section for phytotoxicity warning. thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed (REI 12h Group 4). Systemic seed treatment. For early season protection from corn leaf aphid. CutwormsBlack cutworm is the most common of the many cutworm species that damage corn in New England. Adults are night-flying tan and black moths, while the caterpillars are dark-grey to black and up to 2” in length. Moths from the South arrive between March and June. Eggs are laid mostly on grasses and winter annual weeds, usually near areas of the field prone to flooding. Certain fields tend to have a history of repeated cutworm damage. The larvae feed after dark while hiding under the soil surface during the day. There are 2 to 3 generations per year but usually only the first generation, which produces larvae in May and June, damages corn. Small larvae feed on leaves and occasionally larger larvae cut seedlings off near the soil line. Adults can be monitored with a yellow and white Unitrap from March through May. A catch of over 40 moths before June indicates that frequent spring and early summer scouting is prudent. Scout problem fields weekly, checking at least 100 plants for leaf feeding and cut stems, especially near field margins. Spot spray heavily hit areas or edges of the field if 5% of the plants have been cut down. For best results, make application between midnight and dawn while cutworms are feeding aboveground. Foliar-applied rescue treatments are recommended over preventative soil-applied insecticides. Ground beetles, parasitic flies and wasps and other general predators help reduce populations. When corn follows sod/hay in rotation, fall-plowing may lower cutworm populations by reducing spring egg-laying sites. Weedy and reduced-till fields tend to suffer the most damage.beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A (0 dh, REI 12h, Group 3A). bifenthrin (Capture* 1.15G): 6.4 to 8.0 oz/1000 linear ft. of row (1 dh, REI 18d fresh market, Group 3A). Apply as T-band furrow treatment and incorporate into top inch of soil. Use prohibited in all coastal counties.
carbaryl (Sevin XLR Plus): 2 qt/A (2 dh, REI 12h, Group 1A). chlorethoxyfos (Fortress): 6.0 to 7.5oz/1000 linear ft. of row (REI 48h, Group 1B). Apply in furrow or as a T-band application at planting. For T-band, granules must be incorporated into top inch of soil. Limited to one application per year. chlorpyrifos (Lorsban 75WG): 0.67 to 1.33 lb/A (21 dh, REI 24h, Group 1B). In conservation tillage, apply as broadcast spray to surface preplant, at-plant or preemergence. Postemergence apply to moist soil at night when cutworms are active. Post-emergence spray may be more effective than broadcast. methomyl (Lannate SP*): 1/2 lb/A (0 dh for ears, 3 dh if used for feed or forage, REI 48h, 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 (1 dh, REI 12h, Group 3A). zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A (3 dh, REI 12h, Group 3A). Flea BeetlesThese beetles transmit the bacterium that causes Stewart’s wilt disease and are most troublesome after a mild winter. Start applications when plants are in the spike stage if beetles are present and causing damage. Apply three to four treatments every four to five days. Spunbonded row covers can protect plants against this pest. Some varieties are more tolerant to Stewart’s Wilt (see Sweet Corn Varieties Section). beta-cyfluthrin (Baythroid*XL): 0.8 to 1.6 oz/A (0 dh, REI 12h, Group 3A). carbaryl (Sevin XLR Plus): 1 to 2 qt/A (2 dh, REI 12h, 1A). Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies. chlorpyrifos (Lorsban 75WG): 1.33 lb/A (21 dh, REI 24h, Group 1B). Apply in 9 to 12 inch wide band over the row before corn is 6 inches tall. deltamethrin (Decis* 1.5EC): 1 to 1.5 oz/A (1 dh, REI 12h, Group 3A). esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A (1 dh, REI 12h, Group 3A). gamma-cyhalothrin (Proaxis*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). lambda-cyhalothrin (Warrior*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). methomyl (Lannate SP*): 1/4 to 1/2 lb/A (0 dh for ears, 3 dh if used for feed or forage, REI 48h, Group 1A). See ECB section for phytotoxicity warning. permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A (1 dh, REI 12h, Group 3A). phorate (Thimet* 20G): 4.5 to 6 oz/1,000 row feet in a 7” band over the row at planting and lightly incorporate (30 dh, REI 48h, Group 1B). DO NOT use in furrow. See label restrictions. terbufos (Counter* 15G): 6 to 8 oz/1,000 row feet for any row spacing (REI 48h, Group 1B). Place granules in seed furrow behind planter shoe or in a 7” band over the row, and lightly incorporate. thiamethoxam (Cruiser 5FS): 1.28 to 5.1 oz/100 lb of seed (REI 12h Group 4). Systemic seed treatment. For early season protection from flea beetles. zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A (3 dh, REI 12h, Group 3A). Japanese BeetleThese beetles feed on corn silk, but are usually controlled by sprays directed at controlling ECB and corn earworm. carbaryl (Sevin XLR Plus): 1 to 2 qt/A (2 dh, REI 12h, Group 1A). Highly toxic to bees; avoid use in corn that is shedding pollen. May encourage buildup of aphids by killing natural enemies. pyrethrins + piperonyl butoxide (Pyrenone): 1 tsp/gal, or 1 to 12 oz/A (0 dh, REI 12h, Group 3A). Sap and Picnic BeetlesAdult beetles are 3/16” long and are black, or black with orange spots. The adult beetles survive the winter under plant debris along hedgerows or in fields. Eggs may be deposited in rotting fruit and on silk or in kernels at the tip of the ear. Larvae resemble tiny worms or thin maggots. Populations build when attracted to decomposing fruit, cull piles, or corn ears injured by birds or caterpillars. Ears with exposed tips, especially super sweet and Bt varieties, are susceptible to infestation. To prevent or reduce damage, select varieties that have good tip cover, use clean cultivation, control ear-infesting caterpillars and remove or bury decomposing fruit on a regular basis. Insecticides will not completely control heavy infestations. Seedcorn MaggotSoils that are high in decaying manure or vegetable matter, especially in cool wet springs, attract the egg-laying female flies. If using animal or green manure, treat with: chlorpyrifos (Lorsban 15 G): 8 oz/1,000 linear ft. of row (21 dh, REI 24h, Group 1B). Use as an in-furrow treatment at planting. gamma-cyhalothrin (Proaxis*): 0.66 fl oz/1,000 row feet (21 dh, REI 24h, Group 3A). Band or in-furrow applications. phorate (Thimet* 20-G): 4.5 to 6 oz/1,000 row feet in a 7” band over the row at planting and lightly incorporate (30 dh, REI 48h, Group 1B). DO NO use in furrow. See label restrictions. thiamethoxam (Cruiser 5FS): 1.28 to 5.1 fl oz/100 lb of seed (REI 12h, Group 4). Systemic seed treatment. For early-season protection from seedcorn maggot. Stalk BorerThe eggs of this pest overwinter on grassy weeds. Upon hatching in the spring, the borers feed on grasses. When the larvae become too large to feed within the grass, they migrate into corn fields, attacking border rows. beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A (0 dh, REI 12h, Group 3A). gamma-cyhalothrin (Proaxis*): 2.5 to 3.8 oz/A (1 dh, REI 24h, Group 3A). Wireworms and White GrubTo avoid wireworm problems, corn should not be grown in rotation with sod or grass crops. Delay planting susceptible crops, such as corn or potatoes, on such land for at least two years after the sod has been broken. Summer fallow is recommended for at least one season. Land that was in sod or pasture should be planted to legumes, such as alfalfa or clover, for a year or more before planting corn or other vegetables to reduce the number of white grubs in the soil. Plow or harrow in mid-summer, after harvesting early corn, to reduce grub numbers. chlorpyrifos (Lorsban 15 G): 8 oz/1,000 linear ft. of row (21 dh, REI 24h, Group 1B). Use as an in-furrow treatment at planting. phorate (Thimet* 20-G): 4.5 to 6 oz/1,000 row feet in a 7” band over the row at planting and lightly incorporate (30 dh, REI 48h, Group 1B). DO NOT use in furrow. See label restrictions. |
To purchase copies of the Guide and Photo Supplement, contact your state Extension publication office, or the University of Massachusetts Extension Bookstore at 1-877-UMASSXT (within Massachusetts) or 413-545-2717.