ITHACA, N.Y. -- In the war against a fungus devastating to grapes, Cornell University scientists may have learned mites' real might.

To do battle against powdery mildew, Cornell scientists have turned to the shady underworld of wild grapes. Underneath wild grape leaves exist tiny hairlike structures called acarodomatia. Tydeid mites, as well as other potentially beneficial mites, make themselves at home among them, says Gregory English-Loeb, a Cornell assistant professor of entomology at the university's New York State Agricultural Experiment Station in Geneva, N.Y. What English-Loeb and other Cornell scientists learned is that the mites feed on powdery mildew, which is considered a nemesis to vineyards.

Originally, English-Loeb wondered what ecological role these tydeid mites might play on the grape leaf. They did not appear to feed on the leaf tissue, and, interestingly, he did not find much powdery mildew fungus on plants where the mites were abundant.

Along with English-Loeb, a group of Cornell scientists at the research station began to study interactions between the tydeid mites, acarodomatia and powdery mildew. The scientists are: Robert C. Seem and Wayne F. Wilcox, professors of plant pathology; David M. Gadoury, senior research associate in plant pathology; and Andrew P. Norton, postdoctoral researcher in entomology.

In a series of experiments conducted in the greenhouse and outdoors, the researchers learned that the tydeid mites are capable of dramatically reducing powdery mildew. In one experiment, the mites reduced by 85 percent the powdery mildew's mycelia, the part of the fungus that penetrates and robs the leaf of nutrients. Cleistothecia, the stage of the fungus that overwinters, was reduced by an even greater amount.

Having shown that the mites play an important role in controlling powdery mildew on wild grapes, they wondered if the mites could do the same for popular varieties like Chardonnay, Riesling, Sauvignon B
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Contact: Blaine P. Friedlander, Jr.
bpf2@cornell.edu
607-255-3290
Cornell University News Service
26-Aug-1999