Leek moth threatens plants in St. Lawrence County

An insect blamed for damaging onions, garlic, leeks and related plants has crossed the Canadian border into St. Lawrence County and now poses a threat to growers throughout the state, a county agricultural official said Monday.

"This is not a happy welcome," said Stephen F. VanderMark, a resource educator with St. Lawrence County Cornell Cooperative Extension. "This is a dreaded pest that could become a serious threat to our local growers and large-scale agricultural producers."

Leek moths originated in Europe and arrived in Ontario in 1993. The first confirmed case in the United States was found in Plattsburgh in June 2009.

On Friday, specimens of two caterpillars and one adult moth taken from garlic plants in the village of Canton tested positive at Cornell University's Department of Entomology, Mr. VanderMark said.

There is also a suspected case in Ogdensburg, where crop damage has been found, but no specimens have been obtained yet, he said.

"We've had two calls so far with one case confirmed. I expect we will be getting some more calls," Mr. VanderMark said. "This has gotten the attention of New York state and the U.S. Department of Agriculture."

The adult moths are speckled brown, white and black and lay their eggs on crops of onions, garlic, leeks, chives and shallots.

"When the eggs hatch, the little caterpillars start eating away the leaves. They chew groove-like tunnels into the leaves," Mr. VanderMark said.

Local growers should look for slender, creamy colored caterpillars — the larvae — that are less than half an inch long when full grown. The larvae burrow into plant leaves, feeding on the inside tissues or the leaf surface.

The chewing results in whitish dead patches or streaks running lengthwise down the leaves, according to information from Cornell Cooperative Extension.

The larva then morphs into a pupa with a net-like structure over a cocoon that's attached to the dying foliage. The leek moths have three generations per year, with the worst damage done by the second generation as it moves down the leaves into the bulb, usually in July and August.

"The cocoon has a diamond shape net-like covering that's rather unique," Mr. VanderMark said.

Growers who suspect their plants have been infested by leek moths should bag samples and call Cornell Cooperative Extension at 379-9192.