WOOSTER, Ohio -- The soybean aphid may be back in full force throughout Ohio soybean fields in 2007.
Ohio State University research and Extension entomologists are predicting high population numbers based on recent observations of high adult numbers and increased egg laying on buckthorn -- the overwintering host.
"We sampled buckthorn for the presence of soybean aphids beginning their cycle of overwintering. We found large numbers of winged aphids as well as unwinged individuals," said Ron Hammond, an Ohio State research entomologist with the Ohio Agricultural Research and Development Center. "The significance of these finds are that the soybean aphid is still following the sequence that will in all likelihood lead to larger densities and economic problems next year. Our colleagues from northern states are seeing the same thing. It seems we are right on schedule with our population cycle predictions."
The soybean aphid, a sapsucker relatively new to Ohio, can devastate soybean fields with its voracious appetite if in high enough numbers. Since its discovery in 2001, researchers have annually tracked and accurately predicted its population pattern: high in odd-numbered years, low in even- -numbered years.
Hammond said that researchers speculate the level of soybean aphid populations may be tied to the population of the multicolored Asian ladybeetle, a known predator. Put simply, when soybean aphid numbers are low -- as they were this growing season -- ladybeetle numbers are also low, and when soybean aphid numbers are high, the ladybeetle makes its appearance.
"There were low levels of the ladybeetle this year. That's why the soybean aphid is overwintering in high numbers," said Hammond. "Expect the multicolored Asian ladybeetle to be in high numbers next year in response to high soybean aphids in the field."
Hammond and his colleagues will be traveling the state this fall and winter preparing growers for soybean aphids next year and educating them on best management practices.
Some of those management recommendations include:
• Plant early and then scout fields on a regular basis.
• Treat with foliar insecticides when aphids reach their threshold of 250 aphids per plant. Avoid seed treatments. Although they're effective on very early populations, they do not maintain their efficacy later in the season when aphids reach higher populations and begin their heavy feeding.
• Practice skip-row planting, a technique that prevents spray machinery from damaging plants, thereby potentially reducing yields.
Although the soybean aphid can overwinter in Ohio, most of Ohio's problems come from migrating adults arriving in soybean fields in July from such places as Michigan, Wisconsin and Canada. Common buckthorn, an invasive shrubby tree, is widespread in these areas and north of I-80 in Ohio.
For more information on the soybean aphid, log on to http://ipm.osu.edu/soyaphid/index.htm.