To Virginia Tech Entomologist Ames Herbert, the approaching spring signals the return of the soybean aphid, an invasive insect that can suck the life out of a soybean plant.
Arriving to the U.S. from China in 2000, the soybean aphid multiplied by the thousands in 2001, leaving several north central U.S. soybean farmers with little more than yellow leaves and dried soybeans. Since 2001 the pest has also infested Virginia, but typically arrives later, after most soybean plants have matured. But Virginia farmers still must be watchful — double-crop fields are still vulnerable to the aphid.
For that reason, the Virginia Tech Tidewater Agricultural Research and Extension Center offers a dedicated monitoring and communication system to alert growers to the presence of soybean aphids and recommend management techniques.
In the north central region, once aphids establish themselves in the crop, they are virtually impossible to control without insecticides. In Virginia, however, they usually don't appear before late-July or early-August, during the time when the majority of the soybean crop is mature.
In addition, aphids over-winter in several buckthorn species, weeds that are not common in Virginia. So the lady beetle population is usually adequate to keep most aphids under control.
Last year, most Virginia growers didn't have to use insecticides, saving almost $6 million in pesticide applications. But based on observations of large numbers of aphids surviving the winter last year, entomologists in the Midwest have already predicted a much higher aphid count for this year.
“During low aphid years, the lady beetles don't build as much, so more aphids fly into over-wintering sites,” said Herbert. “Based on the fall flights last year, we're predicting a high aphid count this year.”
To help save growers money both in lost yields and in unnecessary insecticide treatments, the Extension Center offers a variety of services to help keep growers informed of the aphid threat.
Through a USDA grant, Herbert and his staff conduct an extensive survey of about 30 fields throughout the state. And they stay apprised of the aphid count in the north central region via the soybean aphid Pest Information Platform for Extension and Education (PIPE).
“We are a peripheral state, so we gain from the PIPE by seeing how the aphid infestations are progressing in the Midwest,” Herbert said.
In addition to alerts sent over an e-mail listserv from the soybean aphid PIPE, the Extension Center also posts updates on their Virginia Ag Pest Advisory, a free e-mail service that delivers weekly updates on pests of row crops and vegetables. Anyone who wants to sign up for the weekly updates should go to www.sripmc.org/virginia.
Although soybean aphids have not yet caused any crop loss in Virginia, Herbert believes it's best to stay on the lookout.
“It's still reaching outbreak proportions in lots of fields, but not in the Mid-Atlantic states,” said Herbert. “But it has the potential, and the aphid could find other crops or over-winter in other weeds.”