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Aphid Outbreak 2011? | Odd-Numbered Years Can Be Ominous for Soybean-Aphid Infestations

Aphid Outbreak 2011? | Odd-Numbered Years Can Be Ominous for Soybean-Aphid Infestations


2011 could be a year when scouting for soybean aphids should take priority over other items on your yearly to-do list, says Ron Hammond, Ohio State University Extension entomologist.

“All indicators point to what I’d call another potential soybean aphid year in 2011 for Ohio,” he says. “At minimum, soybean aphids will be more common here in 2011 than they were in 2010. So, it’s just a matter of where they will end up and how big a problem they will be.”

Soybean aphids were generally hard to find in most Midwestern soybean fields early in 2010, but Hammond wants farmers to stay vigilant for them this summer. “In 2010, that also held true for much of the Midwest – they just weren’t around in very large numbers early on.”

However, during low aphid years like 2010, population levels tend to start out low in soybean fields in early summer and then begin to build up again during late August and September, prior to aphids taking flight to overwinter on buckthorn, he points out. Right on schedule, “aphid populations started to show up here on buckthorn in late summer during 2010,” says Hammond. As a result, he’s forecasting another potential outbreak in 2011.

“I’m sticking with my two-year cycle as an indicator for potential soybean-aphid problems for Ohio,” says Hammond. “It may be different in other parts of the country, but in the past, the two-year cycle has held up pretty well in our state.”

Other experts are more hesitant to make a prediction on what might happen with soybean aphids in 2011. “For me, making a prediction on soybean aphid problems depends largely on weather conditions during spring,” says Erin Hodgson, Iowa State University entomologist. “So, it’s still too soon to call.”

A mild, calm spring favors soybean-aphid migration, she adds. “If there are good conditions for aphids to fly in the spring, the odds are higher that they’ll be more of a problem in soybeans,” says Hodgson. “In 2010, there were really severe wind and rain events that kept them from flying from their overwintering sites to soybean fields. So, in 2010 their overall population levels were really low throughout the Corn Belt.”

Still, Hodgson acknowledges the tendency for aphid populations to cycle from high to low numbers from one year to another. “I don’t know why, but the even-numbered years typically bring lower aphid population numbers than the odd-numbered years,” she says. “However, for the last couple years, that cycle hasn’t shown as extreme a swing from low to high numbers.”

Spring weather conditions can have a major impact on soybean aphid survival, agrees Hammond. “In 2007, an early April freeze helped knock down their populations quite a bit,” he points out.

Also, trying to predict aphid populations for any given area in Ohio is extremely difficult to do, adds Hammond. “There are likely going to be some areas in Ohio that will need some spraying to control aphids in 2011, but other areas won’t,” he says. “It just depends on the wind currents and where the aphids are coming from. Your location can make a big difference.”

Whether 2011 ends up favoring soybean-aphid survival or not, Hodgson also recommends vigilance. “Start scouting for soybean aphids from bloom through seed set,” she says. “In Iowa, that’s typically from early July through the end of August.” 


January 2011

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