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August Scouting Tips

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Insects to be on the Lookout for in August

Field and Vegetable Crops

Insect: Host(s)DescriptionTreatment Timing*
Blister Beetles: Potato, tomato, melon, eggplant, sweet potato, bean, pea, and many other cropsSlender beetles 1-2" in length which may be black with white margins or black and yellow striped. They feed on the flowers and foliage.Beetles usually appear suddenly and may cause much damage before they are detected. Spot treatments when they are found will give good control.
Cabbage Looper: CrucifersGreen larva with three sets of prolegs and white stripes running the length of its body. When it crawls it moves like an inchworm.Insecticide or "Bt" applications made on 7-day intervals are necessary to control this insect.
Colorado Potato Beetle: Potato, tomato, eggplant, pepper, tobacco, and other solanaceous plantsAdults are yellow with brown stripes, they are oval-convex in shape. The larva is yellowish red or orange and has a row of black spots along each side of its body.For small gardens, beetles can be removed by handpicking; larger areas or heavy infestations will require the use of insecticides.
Corn Earworm: SoybeansEarworm larvae have a wide range of colors, from pale yellow to dark brown; many are greenish. They all have pale stripes and orange-yellow heads.Based on a survey conducted July 19-28, corn earworms are expected to be at high levels this year on soybeans. Scout all your soybean fields, especially ones with open canopies, on a regular basis and treat if necessary. See Report at the end of this Issue.
Cowpea Curculio: Beans and peasThis weevil is 1/4" long, blackish-bronze in color, and has a humpbacked appearance. Adult beetles puncture the pods and lay eggs on the seed. This insect tends to be a problem in home gardens and minor in commercial plantings.Late planted crops tend to be less severely attacked. Crop rotation and sanitation also help in control. Commercial beans will need chemical control starting when blooms first appear.
Cucumber Beetle: Cucumber, cantaloupes, gourd, squash, and watermelon are preferred hosts. They are found on other crops but are not as important.Two beetles feed on cucurbits in Virginia: the spotted cuc. beetle is pale green with black spots on its wing covers; the striped cuc. beetle is pale green with black stripes on its wing covers. Both transmit bacterial wilt of cucurbits.Foliar sprays may be necessary in some cases. To prevent bacterial wilt treat when 1 beetle per 100 row feet is found.
Fall Armyworm: Corn and other grasses as well as many vegetable cropsTan to dark larvae with light colored longitudinal stripes on its back, as well as an inverted "Y" on its head. Start scouting late July and August.For corn and sorghum treat when 80% of the plants have at least one caterpillar, or if there are two or more caterpillars treat corn when 40% infested and sorghum when 50% infested.
Grasshoppers: All cropsThe Differential Grasshopper is dark green with yellow bands. The Redlegged Grasshopper has red legs. Grasshopper damaged leaves are jagged and tattered.Avoid mowing border areas with heavy grass and weed growth; grasshoppers will move from those areas to the crop plants after their host plants have been cut down. Treat with an insecticide if damage becomes severe.
Imported Cabbageworm: Cabbage, broccoli, cauliflower, and other crucifersVelvet green larvae with a faint yellow stripe down the back and a row of yellow spots on each side.Treat when caterpillar populations reach a threshold of one worm per plant, repeat every 5 to 7 days as needed.
Mexican Bean Beetle: Bean cropsAdults are hemispherical in shape and yellowish-brown in color. They have black spots on the wing covers. The larvae are less then 1/2" long and have many spines.Insecticide applications are recommended if more than 30% defoliation takes place.
Spider Mites: Over 180 host plants including many weeds, soybeans and other beans tend to be hard hitDamage is more noticeable than the mites themselves; look for yellow stippled leaves that often take on a sandblasted appearance. Shake the leaves over a piece of paper and look for small pale mites crawling around.Mites tend to be a dry weather problem. Treat with a miticide if dry conditions are expected to continue.
Stink Bug: Many crops but in particular pepper and tomatoBarrel shaped eggs are laid on the undersides of leaves; nymphs are black and white or red or green. Adults are green or tan. All stages have piercing/sucking mouth parts. Damage to pepper and tomato appears as white halos and deformations on the fruits.Removing weedy growth that harbors stink bugs will cut down on native breeding sites. Spot treatments of insecticides when stink bugs are seen is recommended.
Squash Bug: All cucurbits; squash bugs prefer squash, pumpkin, cucumber, and melon in that orderNymphs are grayish white with dark heads and appendages. Adults are oval elongate, light gray, and mottled yellow on the underside. Nymphs tend to be found on the basal portions of the vine.Handpicking works well in small gardens. Chemical control might be needed in larger operations.
Squash Vine Borer: Primarily squash and pumpkin, but other cucurbits are occasionally fed uponPlants suddenly wilt and die; the plants on close examination have white grublike caterpillars boring into the basal portions of the vine.Borers can be cut out with a sharp knife in small plantings; heavily infested plants should be pulled out. Large plantings may need insecticide applications made at the base of the plants.
Thrips: Wide range of field crops, vegetable crops, and floral cropsSmall slender yellow insects feeding on the flowers and foliage. Damaged foliage tends to be spotted with white when heavily fed upon and damaged flowers are brown and tend not to open.This insect tends to be a problem during dry weather and insecticides are only recommended if dry conditions are expected to continue with no rain showers.
Western Corn Rootworm: Corn (only)Pale cream colored larvae tunnel and feed on the roots. The more conspicuous adults feed on the silks during July and August. The adults are pale green with three black stripes on their wing covers, sometimes the black stripes are fused together to make the wing covers appear solid black.Control for adult silk clipping is justified if there are an average of 5 or more beetles per plant and the silk clipping is observed before 75% of the plants have silked. To determine the need for a soil insecticide next year, examine 40 random plants from throughout the field and count the total number of beetles on the entire plant. If the average number of beetles exceeds 1 per plant then you may want to consider using planting time soil insecticides or rotating to another crop. Note: The western corn rootworm is constantly moving east and now may be in counties that did not have them last year Right now it is found as far east as Middlesex Co.
Whitefly: Many vegetable crops, but tomatoes tend to be hard hit.Small dusty white flies found in the underside of the leaves. Pale nymphs are also found on the undersides of the leaves. Their feeding causes the leaves to become mottled with yellow.Insecticidal control is recommended for large populations. This is a very difficult insect to control.

Fruit Insects

Insect: Host(s)DescriptionTreatment Timing*
Codling Moth: Apple and pear primarily, but cherries, peaches, plums, apricots, and similar fruits are also attacked.Pinkish-white caterpillars enter fruit at calyx end and tunnel all the way to the core. Adult moths are grayish-brown with irregular golden brown lines on the fore wings. 1/2-3/4" wingspan.If using pheromone traps, treat if you exceed 5/trap/ week.
European Red Mite: Apple pear, plum, prune, and many other trees and shrubsMites are very small and range from red to green. Foliage turns a sickly bronze color as if covered with dust.This mite is resistant to many miticides, so make sure that the chemical you will use is effective. A dormant oil applied at the 1/2" green leaf stage or earlier in the spring is important also.
Lesser Peach Tree Borer: Peach, plum, cherry, nectarine, apricotLook for brown pupal cases protruding from wounds on scaffold limbs.Treat immediately postharvest.
Peach Tree Borer: Peach, plum, cherry, nectarine, apricotLook for a mass of gum and frass at the base of the trunk; white larvae will be found under the bark from 3" below the soil level to 10" above.Adults emerge July/September, treat immediately post-harvest.
San Jose Scale: Apple, pear, cherry, and many other fruit treesScales are dirty gray with a dark concentric ring on the center. Scales infest the branches, twigs, and fruit.Treat early August in severe cases, otherwise wait until spring. See PMG for timing.
Spotted Tentiform Leafminer: AppleYoung mines are serpentine changing to oval. As the larvae get older they form the leaf into a tentlike structure.Treat young mines with Vydate or Lannate if more than 3 mines per leaf.
Variegated Leafroller and Tufted Apple Budworm: Both are general feeders but are pests on apple and peachEggs are laid in masses in which the eggs overlap much like fish scales. The egg masses are found on the leaves.Treat when egg masses are about to hatch (dark head stage).
White Apple Leafhopper: AppleLook for small, pale, leafhoppers on the undersides of the leaves. This will be the second generation.Check several trees and treat if a high density is found on all trees. This pest may be bad in regions with dry weather.

Ornamental Insects

Insect: Host(s)DescriptionTreatment Timing*
Bagworm: Conifers, maples sycamores, boxelder, and many othersCaterpillars form "bags" around their bodies made of silk and plant debris. They overwinter as eggs in the bags; the eggs hatch in late May and early June.Pick off and destroy all bagworms now and/or treat with an insecticide in mid-June. Early next spring pick off all bags you can find.
Euonymus Scale: Euonymus, bittersweet, and some ivy ground covers.Females are dark brown oyster-shaped, males are elongate and white. Crawler stage is May 5June 10; and Aug. 1-25Treat May 10 and 20, and Aug. 5-15.
Fall Webworm: Most fruit and nut trees as well as some hardwoods and shrubsEggs are laid in a mass of 200 to 500 often covered with a woolly layer of scales. Large groups of larvae form a nest at the tip of a branch.Nests can be pruned out in early summer or if a large numbers of nests exist, treat mid to late-June or when new larvae appear. Nests are still apparent this time of year but control is not warranted for full grown larvae because they have finished feeding.
Japanese Scale: Maple, privetLong and narrow scale, dull white in color, often found on the trunks and branches.Treat at 2-week intervals from June 1-Sept. 1.
Juniper Webworm: Juniper and red cedarWebs will usually be formed on the upper branches and will include frass and dead needles.Prune off and destroy any active webs. Insecticide controls, if needed, should be applied late July-early August.
Mimosa Webworm: Mimosa and honeylocustLarvae feed gregariously in a web spun over the flowers and leaves and later feed individually on leaves and pods.Treat when trees show first signs of feeding in June. May need to repeat in mid-July and mid-August.
Obscure Scale: Oak, pecan, elm hickory, hackberryScales are circular, grayish, and closely resemble tree bark. They can usually be found on twigs and branches. Small branches may be killed.Treat white oak in mid August. Treat red oaks and other trees in mid July.
Pine Bark Aphid: Principally on white pine but on other pines as wellLook for cottony masses on the bark and branches covering small, aphid-like, pale-green insects.Treat late-June and mid-August. Make sure the insecticide is applied with strong stream that penetrates the "cotton". Small populations can be dislodged with a strong stream of water alone.
San Jose Scale: Many trees and and shrubsScales are dirty gray with a dark concentric ring on the center. Scales infest the branches, twigs, and fruit.Treat late July-early August.
Spruce Mite: Arborvitae, spruce, juniper, hemlockSmall mites, 1/50" long, cause a yellow stippling on the needles and dieback of lower branches.Spray with a miticide early fall.
Yellow Poplar Weevil/ Sassafras Weevil: Yellow poplar, sassafras, magnoliaSmall black weevils make rice shaped holes on the underside of the leaves. Larvae make blotch type mines on the same leaves the adults fed upon. This pest has not been as bad this year as it was in 1987 but some trees have had leaves turn brown.Many yellow poplars will have leaves turn yellow and brown prematurely; this is from damage that occurred earlier this year. It is too late for control this year.
White Peach Scale: Most fruit trees and many ornamentalsThe female scale is white with a yellow mark on the center and has a rounded shape. The male is solid white and elongated in shape. Crawler stage is April 25-May 15, and July 1-15, and August 20-September 15.Treat July 5-15, and September 1-10. Next year treat also May 1 and May 10.

* See Virginia Pest Management Guides for recommendations on insecticides and rates. Use insecticide applications only when high population levels demand control action. Most plants can support small populations of pest insects.