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Pests Threaten Ill. Soybean Fields

November 17, 1998

URBANA, Ill. (AP) _ They may be no larger than the period at the end of this sentence, but these tiny pests threaten to invade almost every soybean field in Illinois.

They are called soybean cyst nematodes, and they are responsible for at least $70 million in crop losses each year for Illinois farmers.

A new statewide program encourages farmers to get their soil tested for nematodes, and early results suggest the problem may be worse than expected.

Of more than 1,100 soil samples processed to date, only 8 percent had no indications of soybean cyst nematodes, said H. Walker Kirby, a plant pathologist with the University of Illinois Extension.

Measures such as rotating crops and planting soybeans resistant to nematodes are recommended when more than three cysts are present in 100 cubic centimeters of soil.

In the early testing results, more than 70 percent of the samples were found to have four or more cysts per 100 cubic centimeters of soil. Fourteen percent of the soil samples submitted had 21 or more cysts per 100 cubic centimeters of soil.

Those results demonstrate the need for widespread soil testing, Kirby said.

``The sooner you catch it, the sooner you can get them down to a manageable level,″ he said.

Soybean cyst nematodes do their damage in the plant’s roots.

They have a hollow mouth part _ similar to a hypodermic needle _ that they use to suck nutrients out of cells in the root tissue, Kirby said.

That reduces the nutrients that reach the upper plant, causing the plant to produce fewer pods and to fill fewer of the pods that are produced, resulting in lower yields, Kirby said.

Illinois farmers consistently lose 4 percent to 6 percent of their annual crop because of soybean cyst nematodes, resulting in a $70 to $140 million loss, Kirby said.

Farmers used to believe stunted plants and yellowed leaves were the telltale signs. But researchers now realize that plants can be healthy and green and still be victims of lower-than-normal yields from cyst nematode infestation.

``The only sure way to detect a cyst is a soil test,″ Kirby said.

A new, three-year testing program _ supported by the extension, the Illinois Soybean Checkoff Board and the Illinois Soil Testing Program _ allows farmers to submit soil samples for analysis at reduced prices.

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