Ash borers spotted in North Shore suburb
Thursday, July 13, 2006
by Michael Hawthorne
The affluent North Shore is the latest area of suburban Chicago threatened by the emerald ash borer, an invasive pest that already has killed more than 15 million trees in five states and parts of Canada.
At least one infested tree has been found in Wilmette, Chris Herbert, spokeswoman for the Illinois Department of Agriculture, confirmed this morning. It is the second sighting of the insect in the state.
Arborists have expressed fears that if the beetle is allowed to spread, it could threaten more than 130 million trees in Illinois. Cook County alone has more than 4 million ash trees, and Chicago, 600,000 – one-fifth of all the trees in the city.
By way of comparison, the previous major insect threat here – the Asian longhorned beetle – resulted in the loss of only 1,500 trees since the first sightings eight years ago on Chicago's North Side. This week, experts declared victory over the longhorned beetle after three years without a single local sighting.
Survey crews are heading to Wilmette to look for more signs of the ash borer, like the longhorned an unintentional Asian import. As its name indicates, the emerald ash borer is metallic green in color and feasts on ash trees, gnawing its way into them and slowly killing them.
The beetle first was identified four years ago in suburban Detroit. It since has spread to parts of Ohio, Indiana, Maryland, Virginia and Ontario.
Authorities have spent years preparing for the ash borer's potential arrival in Illinois. Their fears were realized last month when a handful of infested trees were discovered in a housing subdivision west of St. Charles in rural Kane County.
Adult beetles, each barely larger than a penny, emerge in early June and munch on ash leaves before laying eggs in the crevices of an ash tree's bark.
After hatching, larvae chew their way into the tree and begin carving serpentine channels just beneath the bark. The damage cuts the flow of water and nutrients through the tree, weakening and ultimately killing it.
While a handful of insecticides can protect healthy trees, the only proven method to stop the ash borer from spreading is cutting down every tree within a half-mile radius of an infested area.