Aphid watch 2009—
CARROLL – Since last year’s aphid invasion may return for an encore this summer, now’s the time to learn the lessons of 2008.
“We have the potential for a repeat of 2008’s aphid challenges in 2009,” said Marlin Rice, a former Iowa State University Extension entomologist. “I’d say there’s more than a 50 percent chance that we’ll have an aphid problem this year.”
Rice, who spoke at a recent crop meeting in Carroll County, emphasized three keys to manage this pest:
- Remember that the economic threshold is still 250 aphids per plant. Last year was a “perfect storm” for aphids, Rice said. The cold winter decreased predator populations of lady beetles and other beneficial insects, which led to less in-season control.
The cool August proved optimal for aphid reproduction. In 2008, the peak of the aphid population arrived two to four weeks later than in years past.
They thrived in the thousands of acres of late-planted and replanted soybeans, and the warm September night time temperatures extended aphid survival and activity.
- Realize that seed treatments do not prevent aphids from reaching the economic threshold. “Because aphids came so late in the 2008 growing season, seed treatments couldn’t last long enough to keep the populations down,” Rice said.
- Liquid insecticides work equally well when correctly applied. There is no difference between the effectiveness of pyrethroids and organophosphates when they are used correctly, said Rice, who urges growers to use whatever product is most affordable. “Coverage is critical,” added Rice, who cited research showing a two-bushel yield difference when liquid insecticides are applied with fine nozzles versus medium nozzles.
Also, multiple applications don’t offer an advantage over a single application.
You can contact Darcy Dougherty Maulsby by e-mail at firstname.lastname@example.org.
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