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Garlic pest threatens high-value crop

An outbreak of a new crop pest is threatening New York's $24.5 million garlic industry: bloat nematode. The parasite also affects onions, leeks, chives, celery, some varieties of peas and lettuce and other plants. More than 120 plants can serve as a host.

Cornell nematologist George S. Abawi, Ph.D. '70, is on a mission to help save one of New York's burgeoning agricultural commodities: garlic.

Once filling just 11 acres of land in 1992, garlic production has grown exponentially, to 306 acres in 2007, up from 153 acres in 1997. New York is now the fifth largest garlic producing state in the nation. But an outbreak of a new crop pest is threatening the $24.5 million industry.

First spotted by Cornell Cooperative Extension vegetable specialist Christy Hoepting in Orleans County in June 2010, the microscopic stem and bulb (bloat) nematode (Ditylenchus dipsaci) has now been identified in garlic seed and soil samples from 17 New York counties.

Abawi, professor of plant pathology and international agriculture, analyzes the samples at his lab at the New York State Agricultural Experiment Station in Geneva, N.Y.

He recently received a $69,122 grant from the New York State Department of Agriculture and Markets to extend diagnostic expertise to growers statewide in 2012. A portion of the funds will subsidize nematode analysis of garlic and soil samples submitted by growers.

"Stem and bulb nematode has become widely distributed across New York state primarily through infected seed and will worsen if we do not identify the infected seed and soil," Abawi said.

Garlic Seed Foundation Director David Stern says the help will be invaluable to fighting "a real problem that starts slow but grows exponentially, and the next year can decimate your crop."

Some growers have suffered up to 80 percent crop loss, costing them several thousand dollars, as garlic can retail for more than $10 a pound. The parasite also affects onions, leeks, chives, celery, some varieties of peas and lettuce and other plants; more than 120 plants can serve as a host.

"Ten percent of all New York vegetable farms report growing garlic. Its high value per acre makes garlic a financially important aspect of our vegetable industry," said extension specialist Crystal Stewart.

Bloat nematode-infected plants are stunted, with yellow, limp leaves and suffer premature defoliation. Bulbs gradually discolor to dark brown, and become soft, lightweight and cracked.

Young nematodes feed on leaves, stems and bulbs, and adults move into the soil once plant tissues become too degraded. They can then spread to new sites through planting material, on contaminated equipment and by irrigation and surface water runoff.

Abawi said farmers can limit the pest's distribution and damage through crop rotation, debris removal, hot water washing of field equipment and moist soils, as the nematode likes dry conditions.

"Garlic growers must take a holistic approach to production, from site selection and pest control to proper harvesting and storage, and must not transport infected seed or planting material," Abawi said.

Hoepting warned that even "perfect-looking" bulbs can have low levels of nematode that eventually cause problems during production, so it is important to use clean seed. Abawi said clean soil is equally important, so both should be tested.

"Growers do not help themselves by planting clean seed in infested ground," he added.

For more information about how to submit soil and seed samples for testing, contact Abawi at

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