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INSECTS

Introduction

If an insect problem seems likely, check the following:

A chewing/rasping insect feeds on plant tissue and can cause ragged/chewed or missing leaves (e.g., caterpillars, slugs, beetles, grasshoppers), rolled leaves (leafroller), tunnels in between upper and lower leaf surfaces (leaf miners). They can also cause holes in stems, branches or trunk, sections of tree dying, or premature yellowing (wood borers); girdled or dead stems (cutworms, twig girdlers, or stem borers); or general decline of plants due to root damage (soil- dwelling insects).

A sucking insect feeds on plant fluids and injects toxins into the plant. The toxins can cause leaf spotting or stippling (e.g., aphids, leafhoppers, spider mites), leaf distortion such as curling or puckering (or more commonly this can be damage from leafhoppers and thrips), or poisoning of entire plants, resulting in stunted growth and/or yellowing (e.g., scale, mealybugs, mites, aphids, whitefly).

Encourage Beneficial Insects. Naturally occurring predators and parasites of harmful insects are found in gardens, orchards, and fields. Learn to properly identify these species as benefits of your environment. Avoid using pesticides around them. They are as susceptible to insecticides as the pests.

Beneficial Insects and Mites. Many species of beneficial insects and mites can be purchased. Beneficial insects are target specific, and require gardener knowledge of existing pests. Timing of release is an important factor, and if pests are not present, neighboring gardens may benefit more than your garden. In general, these insects have specific requirements for long-term survival, and may need to be released anew each season.

Some Important Practices

• Reduce insect and pest populations by hand removal and regular clean up
• Learn which insects are common to plants growing in your landscape or garden
• Monitor plants in the landscape regularly to recognize when pests are present
• Maintain healthy plants by meeting their cultural requirements (sun, shade, wet, dry…) with the goal of using no or few pesticides which kill beneficial insects, too
• Establish thresholds for acceptable levels of insect infestation
• Provide a sample of an unknown insect to the Help Desk for diagnosis. Mondays and Tuesdays are the best days to bring in samples. Hours are 8 am - 5pm at 8033 Ashton Ave. Suite 105 Manassas, 20109. To save time it is recommended that one call or email

before bringing in a plant or insect. (Call 703-792-7747 or email
master_gardener@pwcgov.org)
• If an insect problem requires chemical controls, contact the Help Desk for more information. Use the least toxic materials according to the label. A certified nurseryman or Extension agent can help you identify the proper and legal pesticide and the method to use it.

Overarching References

Insect Identification Lab, Virginia Tech website provides a means of identifying insects, mites and other pests. See http://pubs.ext.vt.edu/ENTO/ENTO-45/ENTO-45.html

Insect Identification and Diagnosis Request, Virginia Tech is a form for requesting assistance from the Help Desk or State scientists concerning difficult insect problems. See http://pubs.ext.vt.edu/444/444-113/444-113.html

More Resources and References

Garden Insects and Pests, Virginia Tech Publications and Educational Resources provides numerous links to more detailed information on specific insects and pests. See http://pubs.ext.vt.edu/category/garden-insects-pests.html

Some Specific Insects and Solutions

There are numerous insects that have evolved over the years to thrive on ornamental plants, vegetables, fruit trees, woody shrubs, lawn turf and virtually every botanical species. So do not be afraid to ask for assistance.

While not complete, the following are insects that are commonly diagnosed by our Help Desk volunteers:

Aphids: Aphids are one of the most common spring and early summer insects. Any plant that is curled or puckered should be checked for aphids on the underside of the leaves. While they can distort and stunt growth, and spread diseases, they are often attacked by various predators and parasites before they do any serious damage. Affected leaves can often be pinched off, literally nipping the problem in the bud. Plants susceptible: numerous. http://pubs.ext.vt.edu/444/444- 220/444-220.html

Borers:

Azalea Stem Borer: Look for tips dying back and yellow legless grubs up to ½ inch long boring in twigs and trunk. Plants susceptible: azalea, rhododendron, mountain-laurel, blueberry. http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/ort076e/ort076e.htm

Bronze Birch Borer: Look for the top of the tree dying back and up to 1-inch-long flat-headed borers under the bark. Plants susceptible: birch, cottonwood, poplar, aspen. http://ento.psu.edu/extension/factsheets/bronze-birch-borer

Rhododendron Borer: Larvae bore in the sapwood just under the bark, causing the branches to wilt and die. Adults are clear-winged moths. Plants susceptible: rhododendron, sometimes azalea and mountain-laurel. http://ento.psu.edu/extension/factsheets/rhododendron-borer

Caterpillars:

Bagworm: Caterpillars 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. Plants susceptible: conifers, maples, sycamores, box-elder, and many others. Caterpillars are most susceptible to chemical controls at this time of year. http://pubs.ext.vt.edu/2808/2808-1008/2808-1008.html

Gypsy moths: Mature caterpillars are charcoal gray and have black “hairs.” They have 5 pairs of blue and 6 pairs of red spots along their backs. Plants susceptible: over 300 species of trees and shrubs, but they prefer oaks.

http://www.pwcgov.org/default.aspx?topic=040076003150000901

Lace Bugs:

Azalea Lace Bug: Prefers plants in full sun. The tops of the affected leaves are stippled, or bleached out by feeding damage, while the leaf bottoms are covered with small dare excrement spots. Typically damage starts to show up in mid-summer. Plants susceptible: azalea, cotoneaster, pyracantha.

http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/ort039e/ort039e.html

Leaf Miners:

Boxwood leaf miner: Look for yellowed leaves and leaves with small brown spots. This time of year the adult yellow flies may still be found on the foliage. http://ipm.ncsu.edu/AG189/html/boxwood_leafminer.HTML

Holly leaf miner: Look for long serpentine or blotch mines in the leaves. Heavily infested leaves turn yellow-brown. Inside the leaves will be small pale larvae. Plants susceptible: native and English holly. http://woodypests.cas.psu.edu/factsheets/insectfactsheets/html/Native_Holly_Leafminer.html

Scale:

Scale insects come in many varieties, and are generally plant specific. For optimal control, proper identification is necessary.

http://pubs.ext.vt.edu/2808/2808-1012/2808-1012.html

Azalea bark scale: Look for white cottony sacs covering dark red females and eggs on the forks of branches and twigs. Plants susceptible: azalea, blueberry, rhododendron.

Juniper scale: Scales have an elongated white covering with a yellow cap at one end. Crawler stage is from June 5-20.

Maple scale: Look for cottony masses on the undersides of twigs and branches. Foliage on affected branches may turn yellow and the branch may die. Plants susceptible: all maples, locust, white ash, red mulberry, linden boxwood and many others.

Wax scale: A globular off-white scale found on the twigs and leaves. So named because of its waxy color. Plants susceptible: holly, euonymus, pyracantha, boxwood, hemlock, and others.

Squash Bug: Nymphs 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. Plants susceptible: squash, pumpkin, cucumber, and melon, in that order. http://pubs.ext.vt.edu/444/444-031/444-031.html

Stink Bug: Barrel 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. Plants susceptible: many crops, but in particular pepper and tomato.

http://pubs.ext.vt.edu/444/444-621/444-621.html

Some Beneficial Insects. While not complete the below are many insects that are beneficial to the garden and landscape. These insects feed on and control the populations of harmful insects. Spot use pesticides should be a last resort since they may kill beneficial insects and allow harmful insects to run rampant.

Assassin bug - Reduviidaye - The assassin bug feeds mainly on aphids, caterpillars, Colorado potato beetles, Japanese beetles, leafhoppers, and Mexican bean beetles.

Damsel bug - Nabidae - The damsel bug feeds on aphids, leafhoppers, mites, and caterpillars.

Big-eyed bug - Lygaeidae - Big-eyed bugs feed on aphids, caterpillar eggs and larvae, immature bugs, leafhoppers, and spider mites.

Predacious stink bug - Pentatomidae - Predacious stink bugs feed on Colorado potato beetles and various caterpillar larvae.

Syrphid fly larvae - Syrphidae - Fly larvae of this species feed on aphids and mealybugs.

Lady beetle - Hippodamia convergens - The lady beetle feeds mainly on aphids and other soft- bodied insects, such as mealybugs and spider mites.

Green lacewing larvae - Chrysopa camea - Lacewing larvae, known as aphid lions, feed on insect eggs, aphids, spider mites, thrips, leafhopper nymphs, and small caterpillar larvae. Adult lacewings are not predacious.

Predatory mites - Phytoseiulus persimilus and several other species feed on many mite pests, including the two-spotted spider mite.

Trichogramma wasp - Trichogrammatidae - This tiny wasp attacks eggs of more than 200 pest species, including cutworms, corn borers, corn earworms, armyworms, codling moths, and cabbage moths. Release time is critical for their effectiveness since they only attack pest eggs.

Encarsia wasp - Encyrtidae - The greenhouse whitefly is parasitized by this wasp in third and fourth larval instars when Encarsia lay their eggs inside the whitefly scale.

Checked: LGL 9/6/16

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