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An Index of Common Insects Harmful to Trees

The Major Insect Pests of Trees in the United States

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11. Gypsy Moth

Gypsy Moth
USFS/FIDL
The gypsy moth, Lymantria dispar, is one of the most notorious pests of hardwood trees in the Eastern United States. Since 1980, the gypsy moth has defoliated close to a million or more forested acres each year. In 1981, a record 12.9 million acres were defoliated. This is an area larger than Rhode Island, Massachusetts, and Connecticut combined.

12. Hemlock Wooly Adelgid

Hemlock Wooly Adelgid
Kim Nix
The eastern and Carolina hemlock is now under attack and in the early stages of being decimated by the hemlock wooly adelgid (HWA) or Adelges tsugae. 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 cottony-covered insect hides in its own fluffy secretions and can only live on hemlock. The hemlock wooly adelgid was first found on ornamental eastern hemlock in 1954 in Richmond, Virginia and became a pest of concern in the late 1980s as it spread into natural stands. It now threatens the entire hemlock population of the eastern United States.

13. Ips Beetles

Ips Beetle
USFS/FIDL
Ips beetles usually attack weakened, dying, or recently felled southern yellow pine trees and fresh logging debris. Large numbers Ips may build up when natural events such as lightning storms, ice storms, tornadoes, wildfires, and droughts create large amounts of pine suitable for the breeding of these beetles. Ips populations may also build up following forestry activities, such as prescribed burns that get too hot and kill or weaken pines and clear-cutting or thinning operations that compact soils, wound trees, and leave large amounts of branches, cull logs, and stumps for breeding sites.

14. Mountain Pine Beetle

Mountain Pine Beetle
USFS/FIDL
Trees favored by the mountain pine beetle (Dendroctonus ponderosae) are lodgepole, ponderosa, sugar and western white pines. Outbreaks frequently develop in lodgepole pine stands that contain well-distributed, large-diameter trees or in dense stands of pole-sized ponderosa pine. Extensive outbreaks can kill millions of trees.

15. Nantucket Pine Tip Moth

Nantucket Pine Tip Moth
USFS/FIDL
The Nantucket pine tip moth, Rhyacionia frustrana, is a major forest insect pest in the United States. Its range extends from Massachusetts to Florida and west to Texas. It was found in San Diego County, California, in 1971 and traced to infested pine seedlings shipped from Georgia in 1967. The moth has since spread north and east in California and is now found in San Diego, Orange, and Kern Counties.

16. Pales Weevil

Pales Weevil
USFS/FIDL
The pales weevil, Hylobius pales, is the most serious insect pest of pine seedlings in the Eastern United States. Great numbers of adult weevils are attracted to freshly cutover pine lands where they breed in stumps and old root systems. Seedlings planted in freshly cut areas are injured or killed by adult weevils that feed on the stem bark.

17. Hard and Soft Scale Insects

Scale on Yellow Poplar
Purdue University
Scale insects commonly occur on woody ornamentals where they infest twigs, branches, leaves, fruits, and damage them by feeding on the phloem with their piercing/sucking mouthparts. Damage symptoms include chlorosis or yellowing, premature leaf drop, restricted growth, branch dieback, and even plant death.

18. Shade Tree Borers

Metalic Wood Borer
Colorado State Extension Image
Shade tree borers are insects that develop underneath the bark of woody plants. Most of these insects can attack only dying trees, felled logs or trees under stress. Stress to woody plants may be the result of mechanical injury, recent transplanting, overwatering or drought. These borers often are incorrectly blamed for damage caused by a pre-existing condition or injury.

19. Southern Pine Beetle

Southern Pine Beetle
USFS/FIDL
The southern pine beetle (Dendroctonus frontalis) is one of pine's most destructive insect enemies in the Southern United States, Mexico, and Central America. The insect will attack all Southern Yellow Pines but prefers loblolly, shortleaf, Virginia, pond, and pitch pines. Ips engraver beetles and the black turpentine beetle are frequently associated with southern pine beetle outbreaks.

20. Spruce Budworm

Spruce Budworm
USFS/FIDL
The spruce budworm Choristoneura fumiferana is one of the most destructive native insects in the northern spruce and fir forests of the Eastern United States and Canada. Periodic outbreaks of the spruce budworm are a part of the natural cycle of events associated with the maturing of balsam fir.

21. Western Pine Beetle

Western Pine Beetle
USFS/FIDL
The western pine beetle, Dendroctonus brevicomis, can aggressively attack and kill ponderosa and Coulter pine trees of all ages. Extensive tree killing can deplete timber supplies, adversely affect levels and distributions of tree stocking, disrupt management planning and operations, and increase forest fire danger by adding to available fuels.

22. White Pine Weevil

White Pine Weevil
USFS/FIDL
In the eastern United States, the white pine weevil, Pissodes strobi, may attack at least 20 different tree species, including ornamentals. However, eastern white pine is the most suitable host for brood development. Two other North American pine weevil species - the Sitka spruce weevil and the Engelmann spruce weevil-also should be classified as Pissodes strobi.

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