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An Index of Common Insects Harmful to Trees

The Major Insect Pests of Trees in the United States


Here are over 20 insect pests that contribute to health decline and death of many of the trees in the United States. This list of tree insects cause major tree health problems and death. These insects are the cause of significant replacement expense of yard trees and the commercial expense of future losses of forest products.

1. Aphids

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Leaf-feeding aphids are usually not damaging but large populations cause leaf changes and stunting of shoots. Aphids also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus. Some aphid species inject a toxin into plants, which further distorts growth. Here is list of sucking insects provided by Bugwood.org.

2. Asian Longhorn Beetle

Asian Longhorn Beetle
This group of insects includes the exotic Asian longhorned beetle (ALB). The ALB was first found in Brooklyn, New York in 1996 but has now been reported in 14 states and threatening more. The adult insects lays eggs in an opening in the bark. The larvae then bore large galleries deep into the wood. These "feeding" galleries disrupt the vascular functioning of the tree and eventually weaken the tree to the point that the tree literally falls apart and dies.

3. Balsam Wooly Adelgid

Balsam Wooly Adelgid
Adelgids are small, soft bodied aphids that feed exclusively on coniferous plants using piercing-sucking mouth parts. They are an invasive insect and thought to be of Asian origin. The hemlock Wooly Adelgid and balsam wooly adelgid attack hemlock and firs respectively by feeding on the sap.

4. Black Turpentine Beetle

Black Turpentine Beetle
The black turpentine beetle is found from New Hampshire south to Florida and from West Virginia to east Texas. Attacks have been observed on all pines native to the South. This beetle is most serious in pine naval stores, pines stressed for lightwood production, and damaged pines in urban areas.

5. Douglas-Fir Bark Beetle

Douglas-Fir Bark Beetle Damage
Kenneth E. Gibson, USDA Forest Service, United States
The Douglas-fir beetle (Dendroctonus pseudotsugae) is an important and harmful pest throughout the range of its principal host, Douglas-fir (Pseudotsuga menziesii). Western larch (Larix occidentalis Nutt.) is also occa-sionally attacked. Damage caused by this beetle and economic loss if Doug Fir lumber has been extensive in the tree's natural range.

6. Douglas-Fir Tussock Moth

Douglas-Fir Tussock Moth
The Douglas-fir tussock moth (Orgyia pseudotsugata) is an important defoliator of true firs and Douglas-fir in Western North America. Severe tussock moth outbreaks have occurred in British Columbia, Idaho, Washington, Oregon, Nevada, California, Arizona, and New Mexico, but the area subject to attack is more extensive.

7. Eastern Pineshoot Borer

Eastern Pineshoot Borer
The eastern pineshoot borer Eucosma gloriola, also known as the white pine tip moth, American pine shoot moth, white pine shoot borer, and Tordeuse americaine, du pin, injures young conifers in Northeastern North America. Because it infests the new shoots of sapling conifers, this insect is particularly destructive on planted trees destined for the Christmas tree market.

8. Emerald Ash Borer

Emerald Ash Borer
This insect was introduced into North America sometime in the 1990's. It was first reported killing ash (genus Fraxinus) trees in the Detroit and Windsor areas in 2002. Since then, infestations have been found throughout lower Michigan, Ohio, northern Indiana, the Chicago area, Maryland, and recently in Pennsylvania.

9. Fall Webworm

Fall Webworm
The fall webworm or (Hyphantria cunea ) is known to feed late in the season on nearly 100 different species of trees in North America. These caterpillars construct massive silk webs and prefer persimmon, sourwood, pecan, fruit trees and willows. The webs are unsightly in the landscape and generally more numerous when the weather has been warm and wet for extended periods.

10. Forest Tent Caterpillar

Forest Tent Caterpillar
The forest tent caterpillar (Malacosoma disstria) is an insect found throughout United States and Canada where hardwoods grow. The caterpillar will consume foliage of most hardwood species but prefers sugar maple, aspen and oak. Regionwide outbreaks occur at intervals varying from 6 to 16 years in northern areas while annual infestations occur in the southern range. The eastern tent caterpillar (Malacosoma americanum) is more a nuisance than a threat and is not considered a serious pest.

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