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May Scouting Tips

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Insects to be on the Lookout for in May

Field and Vegetable Crops

Insect:Host(s)DescriptionTreatment timing*
Aphids: Any crop but in particular crucifer cropsLook for small soft- bodied insects causing the leaves to be stunted, yellowed, and/or curled.Cut out and destroy small localized areas on plants or treat with an insecticide labeled for aphids and that particular crop.
Black Cutworm and other Cutworms: Many crops but in particular cornMedium to large cater- pillars cut off plants at the base. Inspect newly planted seed beds and newly set plants.If more than 5% of the plants are cut, control with an insecticide or bait is warranted.
Flea beetle: Corn, eggplant, and many other cropsSmall black beetles jumping like fleas when disturbed from the leaves of a plant. They scrape the upper epidermis layer off the leaf and sometimes the fruit, leaving a brown scar.Spray with Sevin when damage becomes severe.
Imported Cabbageworm: Cabbage, broccoli, cauliflower, and other crucifersVelvet green caterpillars with a faint yellow stripe down the back and a row of yellow spots on each side. Full grown larvae are about 32 mm (1-1/4 inches) long.Treat when caterpillar populations reach a threshold of one worm per plant, repeat every 5 to 7 days as needed.
Root Maggots: Many vegetable and field crops, particularly crucifer cropsWhite legless maggots feed on small roots and tunnel into large roots. Plants with damage fail to develop properly.Usually a planting time soil insecticide is needed but a soil drench after plants have been set may be effective. Replanting is effective because there is usually only one generation of maggots and the second planting is not attacked.

Fruit Insects

Insect:Host(s)DescriptionTreatment timing*
Codling Moth: Apple and pear primarily, but cherry, peach,, plums, apricots, and similar fruits are attackedPinkish-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 forewings. 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.
Green Apple Aphid: Apple, pearPale green nymphs on the underside of leaves and new shoots, often a problem on trees with excessive shoot growth due to overfertilization.Treat when 50% or more of the shoots are infested.
Spotted Tentiform Leafminer: AppleYoung mines are serpentine changing to oval. As the larvae get older they form the leaf into a tent- like structure.Treat young mines with Vydate or Lannate if more than 3 mines per leaf on average.

Ornamental Insects

Insect:Host(s)DescriptionTreatment timing*
Azalea Stem Borer: Azalea, rhododendron, mountain-laurel, blueberryLook for tips dying back and yellow legless grubs up to 1/2" long boring in twigs and trunk.Treat mid-May and mid-June with an insecticide or cut out and destroy dead and dying tips as noticed. Use of a borer paste in the holes will give some control also.
Boxwood leafminer: BoxwoodAdults are out April to early May. Infested leaves often appear blistered and discolored. See the March 1990 issue of the Plant Protection Newsletter for more information.Apply insecticides for adults; apply systemic insecticides in early to late June to control larvae.
Boxwood Mite: BoxwoodWhite and gray stippling on the upper surface of the leaves.Treat in early May with a miticide.
Bronze Birch Borer: Birch, cottonwood, poplar, aspenLook for the top of the tree dying back and up to 1" long flat-headed borers under the bark.Treat mid-May, and early-, mid-, and late-June; spray trunk and branches heavily and leaves lightly.
Camellia Scale: CamelliaScale is light to dark brown, 1/10" long and oyster-shaped. Crawler dates are May 1- June 5; and Sept 15-30.Treat May 10 and 20 and/or Sept. 10 and 20.
Dogwood Borer: Dogwood, some- times pecanAs many as 50 white caterpillars with brown heads living under roughened areas of the bark.Treat mid-May, repeat at 6 week intervals 2-3 times.
Dogwood Twig Borer: Dogwood, elm, viburnum, and many fruit treesA slender lemon-yellow beetle grub feeding in the center of twigs. As it feeds it makes small holes to the outside for the protrusion of frass.In early to mid-May, apply an insecticide spray to control the adults. Prune out and destroy infested twigs.
Eastern Tent Caterpillar: Many fruit trees but in particular cherryLook for conspicuous egg masses circling twigs. These egg masses will be black in color and quite shiny as if varnished. The small black hairy caterpillars will hatch out in April and feed on the newly emerging leaves.Pick off egg masses before they hatch. Treat with an insecticide as soon as the leaves have emerged enough to retain the insecticide.
Elm Leaf Beetles: ElmNewly hatched larvae are yellowish with black markings, adults are olive green with two black lines.Control newly hatched larvae in late-May and early-June.
Euonymus Scale: Euonymus, bittersweet, and some ivy ground coversFemales are dark brown oyster-shaped, males are elongate and white. Crawler dates are May 5- June 10; and Aug. 1-25.Treat May 10 and 20, and Aug. 5-15.
Florinia Hemlock Scale: Hemlock fir, spruce, yewCast skins give trees a white-washed appearance with many scales on the undersides of needles. Scales under close examination are yellow in color. Crawler stage peaks May 15-June 20.Treat May 20-25 and June 5-10.
Hickory Leaf Stem Gall: HickoryGalls shaped like bullets develop on the petioles and shoots. Leaves with galls fall off the tree prematurely, causing concern by the tree’s owner. Galls are formed by aphids.No control is needed on established trees as these galls do not harm large trees seriously. Young nursery stock can in some cases be killed and an insecticide applied just as the leaves open may be warranted.
Lace Bugs: Andromeda, oak azalea, walnut rhododendron, sycamoreNew damage will not be apparent yet this year, but last season's damage appears as stippling and brown droppings on the leaves.Lace bugs overwinter as adults on deciduous plants. Treat in late May and repeat in June and July. On ever- greens, lace bugs overwinter in the egg stage.
Lilac Borer: Lilac, ash, privetLook for the white borer 3/4-1" long just beneath the bark.Control adults with an insecticide in early May and repeat 6 weeks later. Borers can be killed in their burrows with borer paste or a long flexible wire.
Oystershell Scale: Most fruit trees and many ornamentalsScales are dark brown and oyster shaped. They can build up to extreme numbers at times and almost completely cover twigs and small branches. Crawler dates are May 1- 20 and July 15-25.Treat May 5-10 and/or July 15-20.
Pine Needle Scale: Nearly all species of pine as well as many other ever- greens.The female scale is white and about 1/10" long, its shape varies but is usually wider at one end. The male is smaller and has four parallel ridges down the center. Crawler dates are April 20- May 30 and July 10-20.Treat May 5-20 and/or July 15-20. Single infested branches can be pruned out.
Southern red mite: Holly, pyracantha, azalea, rhodo- dendron, camellia, and other broad- leaved evergreensDamage is seen as finely stippled leaves with a yellowed, chlorotic, or russetted appearance.Treat: late April to early May and late September to mid- October.
Spruce Mite: Arborvitae, spruce, juniper, hemlockSmall mites, 1/50" long, cause a yellow stippling on the needles and die- back of lower branches. In severe cases older branches may turn brown and die.Spray with a miticide in mid-May and early fall.
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 dates are April 25-May 15, and July 1-15, and August 20-September 15.Treat May 1 and 10, July 5-15, Sept 1-10.
White Pine Weevil: Pines and sprucesThe larva is a yellowish, legless, grub that feeds under the bark on the terminal leader. The leader wilts and droops in the spring indicating the presence of the grub.Prune and destroy infested shoots in May and June.

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