Soybean aphids, a potential agricultural threat, found by Cornell entomologists in New York state
By Blaine Friedlander
Potentially damaging soybean aphids have been detected in several central and western counties of New York state, according to Cornell University entomologists. The insect has infested several other agricultural states since last summer, particularly Michigan, Wisconsin, Minnesota and Illinois.
Soybean fields in New York state have been surveyed at random by Cornell entomologists since June 28. They found low numbers of the soybean aphids (Aphis glycines Matsumura) in Cayuga, Erie, Genesee, Monroe, Niagara, Ontario, Orleans, Seneca, Wayne, Onondaga, Oswego, Jefferson, Tompkins and Yates counties.
At risk is the expanding New York soybean industry. Once minuscule, soybean acreage in New York has grown to about 140,000 acres this year from an estimated 40,000 acres in 1990, according to statistics from the New York State Department of Agriculture and Markets. Dairy producers use soybeans as a rotation crop, as a source of livestock feed and as a cash crop option. Last year's New York receipts for soybeans totaled $22.4 million.
"This is a growing industry in New York, and we want to keep on top of new pest problems as they arise," says John Losey, Cornell assistant professor of entomology and the state's primary investigator in the Multi-State Soybean Aphid Survey, funded by the Northeast Region Soybean Promotion Board. "We have only been sampling for several weeks, so we don't yet know the extent or severity of the infestation."
Soybean pest concerns have been small in the Northeast, according to Keith Waldron, Cornell's New York State Integrated Pest Management Coordinator for livestock and field crops and a co-investigator on the aphid survey. "Given our northeastern pest spectrum, most pest impacts can largely be minimized or avoided through an integrated approach based on selecting varieties for maturity group, disease resistance, commercial attributes and the timely implementation of sound agronomic practices including crop rotation," he says.
Fortunately, the aphids have a natural enemy: ladybugs, which can eat as many as 5,000 aphids in a lifetime. Scouting is the best way to find the aphids. "Given our complement of potential pests, field monitoring is most efficient when conducted during crop emergence, mid-vegetative and reproductive growth stages," Waldron says.
As part of the their participation in the aphid survey, the Cornell scientists have hired undergraduate students Lee E. MacOmber, a senior from Hatfield, Pa., and Brett N. Scott, a senior from Atlanta, to conduct a field-by-field search for the aphids. So far, MacOmber and Scott generally have had very few aphids per leaf. E. Richard Hoebeke, assistant curator of Cornell's Entomology Collection, has made positive identification of the aphids. Entomologists first reported finding the aphids in North America last July, when they were discovered in Wisconsin soybean fields. Subsequently, the aphids were found in Indiana, Iowa, Kentucky, Missouri, Ohio, West Virginia, Illinois, Michigan, Pennsylvania, Minnesota, Florida and, most recently, in Ontario, Canada.
The aphids have the potential to transmit any number of infectious viruses from one field to another. These viruses include alfalfa mosaic, soybean mosaic, bean yellow mosaic, peanut mottle, peanut stunt and peanut stripe. However, transmission of these agricultural viruses has yet to be documented in the United States.
Native to China and Japan, the soybean aphid is a tiny, pear-shaped, yellow arthropod with distinct black cornicles, which are wax-secreting tubes that project out from its abdominal area. It lives on the stems and young leaves of soybean plants.
The aphids produce as many as 15 to 18 generations each year. Nymphs hatch in the spring. After two generations of wingless females, a generation of winged females migrates from buckthorn shrubs in search of soybean plants, according to the North Central Pest Management Center in East Lansing, Mich. During the summer, a series of wingless generations develop in the soybean fields followed by a winged generation that departs its host plant in search of other soybean plants.
By the autumn, the winged female aphids migrate back to buckthorn, their winter host. These females then produce a generation of wingless females that lay eggs near the buds on buckthorn twigs.
Survey efforts will concentrate on early and rapid detection of the soybean aphid throughout the state. The Cornell scientists are sharing their findings with other entomologists in the Northeast, with state agencies and with the USDA's National Agricultural Pest Information System and the agency's Cooperative Agricultural Pest Survey and Animal Plant Health Inspection Service.