The emerald ash borer, here with wings spread, has caused the death of approximately 25 million ash trees in less than a decade.
The larvae, which measure 2 to 3 centimeters in length, burrow their way through the inner layer of the ash tree's bark, impeding its ability to conduct water and nutrients throughout the tree.
Emerald ash borer larvae leave a distinctive serpentine-shaped tunnel on the surface of the wood just under the bark.
When the larvae finally emerge from the bark as adults, they typically leave a D-shaped exit hole in the bark.
Adult emerald ash borers, members of the metallic wood-boring beetle family, measure only a half inch in length by 1/8 inch wide and are a striking, bright metallic green color. The adult beetles, nibbling only on leaves, are relatively harmless to the trees. It’s their ravenously hungry larvae that are causing all the destruction.
Emerald ash borer traps, hanging on trees near to ash trees, attract the beetle by a combination of color and scent. The beetles become stuck to the traps, which have a sticky surface.
The Asian longhorned beetle feeds on many species of hardwood trees. This beetle has been accidentally introduced to North America from China. Currently, there are known infestations in the New York City metropolitan area, the city of Worcester Massachusetts, and Ontario, Canada.
Chestnut blight is caused by an exotic fungus that attacks twigs, branches, and trunks, causing cankers that eventually girdle the tree. It is believed that the disease was imported to North America in the late 1800s on Japanese chestnut nursery stock, and distribution of successive importations was the major factor in the spread of the pathogen.