Friday, August 29, 2008

Sorting out threatening tree insects

August 28, 2008


A rogue's gallery of insects continues to devastate the area's landscape and forest trees: the emerald ash borer, the Asian longhorned beetle, the gypsy moth and the elm bark beetle.

The emerald ash borer, an Asian native, was discovered in southeastern Michigan in 2002. It was probably brought to this country in wooden crates on cargo ships and planes from its native Asia. The borer showed up in Ohio in 2003; in Indiana in 2004; in Illinois and Maryland in 2006; and in western Pennsylvania and West Virginia in 2007, according to the U.S. Department of Agriculture.

The emerald ash borer is responsible for the loss of 40 million trees in southeastern Michigan alone, as well as millions more in Ohio, Illinois, Pennsylvania, West Virginia and Virginia. Thanks to a multi-state effort, the insect even has its own website:

The Asian longhorned beetle likes to feast on the hardwoods -- maple, birch, horse chestnut, poplar, willow, elm and ash trees. Like the emerald ash borer, it probably arrived in shipping crates and pallets. Infestations have been reported in New York, New Jersey and Illinois.

It was first spotted in Chicago's Ravenswood community in 1998. In Chicago alone, the Asian longhorned beetle caused the loss of 1,551 trees.

According to the USDA's National Invasive Species Information Center, the gypsy moth emigrated to American in 1869 in an ill-advised attempt at domestic silk production. It has been known to completely defoliate trees.

University of Illinois Extension reports its favorite leaves are oak, crabapple, linden, poplar, beech, willow, birch, sweetgum, serviceberry and hawthorn. But the gypsy moth isn't fussy. In a pinch, it will also devour sycamore, Indian bean, honeylocust, dogwood, juniper, yew, lilac, arborvitae, arrowwood and tulip leaves.

Dutch elm disease, first identified in the Netherlands, is a fungal disease -- Ophiostoma ulmi -- which is spread from tree to tree by the elm bark beetle. It came to the U.S. in 1931, in a shipment of logs from France to Cleveland, Ohio. The disease caused the loss of 77 million American elms by the 1980s. Work is being done to breed Dutch elm resistant American elms by the U.S. National Arboretum in Washington, D.C.


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