What is in this article?:
- Close watch on soybean pests could reduce insecticide use
- Defoliation may not warrant spraying
- Controlling soybean bean leaf beetles
- Other soybean pest problems
- Instances of tolerance to pyrethroids
Careful monitoring of insects in soybean fields and assessing how much threat they pose to crop yield could result in fewer insecticide applications and greater cost savings, says Angus Catchot, associate Extension professor of entomology and plant pathology at Mississippi State University.
Defoliation may not warrant spraying
“I was shocked. The first thing that popped into my mind when I saw the results was, if there’s no yield loss at 100 percent early season defoliation, we potentially wasted applications on 150,000 acres of soybeans that we treated for gray loopers last year early in the season.
“Admittedly, had they been my soybeans, I probably would’ve been spraying, too — but if you’ve got just a 5 acre spot that’s defoliated in the middle of a 100 acre field, it’s probably not a catastrophic event and you might hold off on spraying the field. We’re going to follow up on this with more study.”
The soybean insect situation in 2010 was quite variable, Catchot says.“When soybeans were just coming out of the ground last year — anywhere from cotyledon to seedling stage — we started getting calls from across the state about soybean loopers.“Cabbage loopers, I said. There’s no way we’d be seeing soybean loopers in June. Then I started getting calls telling me ‘They’ve got black front legs.’ We started making collections and found we had gray loopers. They look a lot like soybean loopers, but are a different species.
“We’ll have an outbreak of gray loopers maybe every 20 years or so. In high numbers, they can cause extensive defoliation, and numbers were high enough that we treated about 150,000 acres.
Once we figured out what they were, we could make treatment recommendations. Unlike soybean loopers, which require some rather costly applications, we could control gray loopers with very low rates of pyrethroids.”