LACONIA — Nearly a year after the emerald ash borer, the gravest single threat to hardwood forests, was found in Concord, Scott McPhie of the city's Planning Department is preparing to scout for signs and take steps to manage the appearance of the insect in the city and its environs.
McPhie said recently that he will suggest that the Conservation Commission begin taking an investory of ash trees in the city and recommend that the Planning Board discourage landscapers from planting ash trees.
Piera Siegert, the state entomologist at the New Hampshire Department of Agriculture, said that the emerald ash borer originated in China, entered the United States from Canada in the 1990s and was first identified in Detroit in 2002. Since then the insect has destroyed millions of ash trees across the Midwest. The emerald ash borer was found in New York, Connecticut and Massachusetts in 2012 and so far the infestation in Concord, which seems to have spread over 24 square miles along the Merrimack River, is the only confirmed presence of the pest in New Hampshire.
Siegert explained that the life cycle of the insect makes it difficult to detect before it has done lethal damage to the trees. The female lays her eggs on the tree in the summer and when the larvae hatch they burrow into the cambium layer of the tree. Between the bark and sapwood, the cambium layer is the growing part of the tree that produces new bark and wood. The larvae, feeding on the tree, carve serpentine galleries within it, effectively girdling the tree. Siegert said that two or three years may pass before the first signs of decline become visible and within three to five years the tree will be dead.
While female emerald ash borers will fly considerable distances to find a suitable tree to lay her eggs, Siegert said that the insect has continually expanded its range with the help of human beings, primarily through the transport of infested firewood and nursery stock. Once the insect was found in Concord, Merrimack County was placed under a quarantine, prohibiting the export of firewood, nursery stock and other infested material from the county.
McPhie said that since the emerald ash borer attacks only ash trees, taking an inventory, particularly of the mature trees preferred by the insect, would increase the likelihood of discovering an infestation before it becomes widespread. At the same time, residents can be informed about how to identify the emerald ash borer, a metallic green insect about a half-an-nch long and an eighth of an inch wide, and signs of its presence. For example, the insect was found in Concord by a resident who noticed intense activity of woodpeckers on an ash tree. Siegert said that there is abundant information about the emerald ash borer on the website nhbugs.org.
There are an estimated 25 million ash trees of at least five inches in diameter in New Hampshire and another 750 million saplings and seedlings, altogether representing approximately six-percent of the northern hardwood forest.