In 2009, aphids were found early in the season in Ohio, leading to expectations of a major infestation. “Aphids built up heavy in northeast Ohio and locations along Lake Erie, but nowhere near what we had expected,” says Ron Hammond, Ohio State University Extension entomologist. “By contrast, we found aphids in southern Ohio for the very first time and beyond threshold numbers. Aphid populations elsewhere were practically nonexistent, so we’re not sure where those populations in the south came from.”
Hammond adds that other states throughout the Midwest were experiencing the same phenomenon — exploding populations across southern counties with the central part of the state generally void of the pest.
This May, Hammond and his colleagues were predicting low populations in 2010 for a reason they didn’t anticipate: a fungal pathogen, at the right place and right time, wiped out much of the winged aphids on buckthorn, so very few eggs had been found this year in areas like Ohio and Michigan.
That quickly changed in June, when Hammond’s team found plants with 30 to 50 aphids on them, some with more than 100 aphids, in early-planted fields in the north central part of Ohio. “Based on this assessment, the soybean aphid has the potential to be a huge economic problem we expect in odd-numbered years,” he says. Early-planted soybeans, especially those without a seed treatment, may be more susceptible.