Asian Aphid to Up Farm Costs

Aug. 17, 2000 -- An Asian aphid, newly found infiltrating Midwest soybean fields, could mean higher costs for some U.S. farmers, but will not affect government estimates for a record soybean harvest this year, a U.S. Agriculture Department official said Thursday.

USDA officials on Wednesday concluded that for the first time in a decade a foreign pest had invaded Midwest farms, munching away on soybean crops in Michigan, Illinois, Wisconsin and possibly Minnesota.

Formally called the Apis glycines, the tiny soybean sap-sucking aphid originates from China and other Asian countries but has never before been seen in North America.

Charles Schwalbe, an entomologist with the USDA’s Animal and Plant Health Inspection Service, said the new pest will mean higher expenses on pesticides for some farmers. “Realistically, soybean farmers will encounter additional costs,” Schwalbe said. “But, it’s unlikely that this is going to be a massive outbreak of devastating proportions.”

John Wedberg, University of Wisconsin entomologist, said there was no evidence that the Asian aphid would have any negative impact on commodity markets. The USDA last week estimated this year’s soybean harvest would be the largest ever at 2.9 billion bushels.

Weather Triggers Outbreak

Scientist predict the Asian aphid may have hitchhiked its way to the U.S. Midwest on a woody plant from Asia within the past few years. “Like many pests, they can exist at very innocuous levels and quite easily go unnoticed until something triggers an outbreak,” Schwalbe said.

Hot temperatures, high humidity and heavy rainfall are suspected causes for the sudden outbreak. Discovered in late July by University of Wisconsin students, the Asian aphid damages soybean crops by sucking a plant’s sap. Scientists also think the pest may transmit deadly viruses to the crop.

“Double crop beans planted in late May to mid-June seem to have the heaviest population” of aphids, said Wedberg, who found hundreds of the pests on a single soybean leaf in a field near Madison, Wisconsin. “If farmers are finding the aphids now it is too late,” he added.

Common Fungus Kills Aphids

The USDA said it was too late to quarantine fields to control the outbreak, and instead was informing growers in all 50 states about how to identify the pest and possible ways to kill it. Insecticides such as pyrethrodis and dimethoate may help control the aphids, according to experts.

“You cannot prevent the spread,” Schwalbe said. “There is little that can be done practically speaking.”

The good news for Midwestern soybean farmers is that a common fungus seems to bedestroying a significant portion of the Asian aphids, according to Wedberg. Scientists are scrambling to learn more about the Asian aphid and aim to have better advice for farmers this winter about how to control future outbreaks.

The last major foreign pest to invade Midwest crops was the Russian wheat aphid, which caused about $1 billion of damage to U.S. wheat fields since it arrived from Mexico in 1989. Preliminary USDA estimates value the nation’s entire 2000 soybean crop at about $12.45 billion.