Lang talks about aphid resistant soybean varieties
By Jean Caspers-Simmet
simmet@agrinews.com
Date Modified: 07/22/2010 9:18 AM
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NASHUA, Iowa —Aphid resistance in soybeans offers another tool for fighting the pest that can devastate soybean fields, says Brian Lang.
The Iowa State University Extension field agronomist talked about this issue during a recent field day at the Northeast Research Farm at Nashua.
Single gene resistance is available now, Lang said. Single gene resistance makes it easy to breed into soybean varieties, but the bad part is that resistance can more easily be overcome.
The first gene to be commercialized, named Rag1, was first identified by scientists at the USDA. Rag2, 3, 4 and 5 have since been identified. Syngenta sells soybeans with Rag 1 and Pioneer should soon have varieties with the Rag1 gene, Lang said.
Research at Nashua showed that Rag1 worked well.
"There is concern that there could be slippage of the technology if we get a migration of aphids into the area of a different biotype not resistant to Rag1," Lang said. "Even if you plant host-plant resistant soybeans, you still want to scout your soybeans. There is a chance treatment will be required, but the gene so far is doing a good job of holding down aphid populations. With Rag1, the aphids are still in the fields feeding and reproducing but very slowly. The technology will advance."
Lang provided an update on soybean aphid numbers so far.
"If you are east of Highway 63, you are probably finding some," Lang said. "West of Highway 63 you probably aren't finding any."
With wet cloudy weather, aphid numbers haven't progressed. Lang found his first aphid March 31. He scouts 12 Winneshiek County fields on a weekly basis. A few weeks ago, half the fields had aphids. During his last check, most colonies had either decreased or gone away.
As of June 27, at Lang's Decorah research plots, all plants had one or two aphids except one plant, which had four.
"The numbers are ridiculously small but that's OK," Lang said. "We'll scout weekly and let you know what we find."
Lang said this time of year he gets calls about putting insecticide in with the last Roundup pass.
"As low as these aphid pressures are that is definitely not a good idea," he said. "That kills beneficials out there. Leave the insecticide out, it's not going to help."