There are many insects that attack hardwood trees which ultimately cause death or devalue a tree in the urban landscape and rural forest to the point where they need to be cut. Five of the most costly and aggressive insects have been suggested by foresters and landowners at About's Forestry Forum. I have ranked these insects according to their ability to cause aesthetic and commercial damage. Here they are:
#1 - Gypsy Moth:
The exotic gypsy moth is one of the "most notorious pests of hardwood trees in the Eastern United States." Since 1980, the gypsy moth larvae has defoliated close to a million or more forested acres each year. The moth was introduced into the United States in 1862.
The insect lays visible buff-colored egg masses as leaves emerge in the spring. These masses hatch into hungry larvae that quickly defoliate hardwoods. Several defoliations can frequently kill trees
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#2 - Emerald Ash Borer:
The Emerald ash borer (EAB)is an exotic, wood-boring beetle discovered in Michigan in 2002. EAB is blamed for killing millions of ash trees annually and forcing quarantines on firewood
and tree nursery stock in several states. The EAB could potentially decimate arboricultural ash plantings and natural ash stands in the eastern United States.
The EAB larvae feed on the cambial bark. These S-shaped feeding galleries will kill limbs and can ultimately girdle the tree.
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#3 - Longhorn Beetles/ Borers:
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.
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#4 - Elm Bark Beetle:
The native elm bark beetle and/or the European elm bark beetle is critical for overland spread of Dutch elm disease (DED) and is worthy of being included in this "worst" list. The DED fungus is transmitted to healthy trees in two ways: bark beetles transmit spores from diseased to healthy trees and root grafting can also spread the disease when tightly spaced. No native elms are immune to DED but the American elm is especially susceptable.
More on Dutch elm disease
; elm bark beetle
#5 - Tent Caterpillars:
The eastern (ETC) and forest (FTC) tent caterpillars are first seen in the spring in eastern U.S. deciduous forests. The ETC makes its nest in the fork of branches. The FTC actually builds no tent but is by far the most destructive of the two.
The favorite food of tent caterpillars is wild cherry but oaks, maples and many other shade and forest trees are attacked. The FTC can strip extensive stands of trees of all leaves. The attacked tree's growth is effected. More on forest tent Caterpillar