A new pest threat might pose problems for St. Lawrence County gardeners and commercial growers of onions, garlic, leeks, shallots, chives, and related crops.

An infestation of leek moth appears to be spreading in the county, according to Steve VanderMark, Senior Extension Resource Educator at Cornell Cooperative Extension of St. Lawrence County.

In June, VanderMark says, a Canton gardener brought him a specimen of garlic that tuned out to have leek moth on it, “an entirely new pest to our immediate area and the second detection of this pest in the U.S.

“Additional infestations have been confirmed in the county since the first one in June,” and have been found in Canton, Potsdam, Russell, Waddington, in areas south of Massena and west of Ogdensburg, and a suspected infestation in Morley, VanderMark says. He says growers in those areas should pay close attention to their crops.

He says he wants gardeners and other growers of onion-family crops to immediately inspect their plants, to look for larvae, or a worm-like stage, feeding on top of and within leaf material, or other evidence of their presence. After several weeks of feeding, the larvae climb out on the foliage and spin cocoons, which open to release brownish moths about 12 days later. After reproduction, they lay eggs and the cycle begins again. Their numbers and the damage they cause usually increase as the season goes on.

There do not appear to be many alternatives for preventing and removing the moths and their other stages. VanderMark says the best alternative seems to be covering rows of plants to prevent egg-laying. No effective pesticides are available.

VanderMark says anyone who has what they believe is a leek moth infestation should call the extension office at 379-9192 for diagnostic procedures.

You can get more information on the web at cce.cornell.edu/Ag/Horticulture/Pages/default.aspx; enter “leek moth” in the search box. Much more information is available from several other sources on the web.

There does not appear to be a repeat of the late blight infestation that damaged tomatoes, potatoes and other crops last year. That organism was imported and is not native to the region. There was one suspected case this year, County Cooperative Extension says, but that turned out not to be late blight.