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Research team tackles top pests that scourge organic crops

Foodies in search of organic cucumbers may find themselves in a pickle: A new strain of downy mildew is causing many organic growers to abandon the crop.

Cucurbit downy mildew, a particularly explosive pathogen, has joined other pests like striped cucumber beetles and aphid-vectored viruses in threatening cucumbers and other crops.

But now, Cornell researchers are teaming up with colleagues along the East Coast to support the organic production of cucumbers, melon and squash by addressing these pests.

A $2 million grant from the U.S. Department of Agriculture's National Institute of Food and Agriculture Organic Agriculture Research and Extension Initiative will fund a four-year project that will allow an interdisciplinary team of eight Cornell breeders, plant pathologists, entomologists, economists and extension specialists to attack the problem on several fronts:

Michael Mazourek, Ph.D. '08, the Calvin Noyes Keeney Assistant Professor of Plant Breeding and principal investigator for the project, said these strategies will help many organic growers who currently avoid cucurbit crops because of these pests.

"Since 2003, the acreage devoted to pickling cucumbers has declined by 20 percent as a direct result of the cost and risk associated with downy mildew," said Mazourek.

He added that the fundamental practices used by organic farmers to control pests -- soil building, rotation, plant variety and allowed insecticides and fungicides -- are not completely effective against these insects and diseases, and growers often feel little can be done to manage the problem.

But Cornell researchers have found some solutions that may be effective.

Unheated or minimally heated greenhouses have already been adopted by many organic farmers to extend the Northeast growing season, and early studies suggest that such environments may also help reduce or eliminate cucurbit downy mildew. Copper products may also reduce the severity of the disease, according to research by Christine Smart, associate professor of plant pathology.

What's more, strategic inter-row cropping of other vegetables, such as the perennial legume sericea lespedeza, may provide depositories for viruses when aphids enter fields, and entomologist Michael Hoffmann, director of the Cornell University Agricultural Experiment Station, is examining whether induced plant volatiles or attractive early flowering squash "trap crops" might help control striped cucumber beetles.

Mazourek has also bred several promising disease-resistant varieties of cucumber and squash.

"We have the genetics for host resistance and management approaches that have proven effective in preliminary trials and on-farm studies," Mazourek said. "Further experimentation with these approaches will lead to innovative crop production strategies that will benefit the entire East Coast region."

Additional collaborators on the project include researchers and growers in North Carolina and Alabama, where squash is a particularly important crop.

"Given the anticipated increase in pest pressure associated with a warming climate, cucurbit research done today in more southerly regions will ultimately benefit agricultural systems to the north as shifts in distribution in pests and crops occur," Mazourek said.

Stacey Shackford is a staff writer for the College of Agriculture and Life Sciences.

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