What is in this article?:
- Bollworms increasingly a problem in Mississippi soybeans
- Bollworms harder to control
- Grain sorghum headworm complex
“We sprayed almost no bollworms in Mississippi soybeans until 2006," says Angus Catchot, associate Extension professor of entomology and plant pathology at Mississippi State University. "But now we’re on an incline where we’re spraying more and more — last year we treated around 750,000 acres an average of two times. The acreage is growing every year, and we’re seeing more pyrethroid-resistant bollworms.”
KEITH GRIFFIN, from left, Chemtura AgroSolutions, Orlando, Fla.; Dave Cummins, Bayer CropScience, Madison, Miss.; and Manley Gilliam, also with Chemtura, Santa Rosa Beach, Fla., were among those attending the Mississippi Agricultural Consultants Association annual meeting.
Bollworms harder to control
Treatment threshold is 9 bollworms per 25 sweeps, he notes. “If you’re getting 12 bollworms per 25 sweeps and you make a pyrethroid application, then get 6 bollworms per 25 sweeps, you may think, ‘Well the pyrethroid got me below the threshold.’ But, you only got 50 percent control. And if you’re catching 20, or 75, or 100 bollworms per 25 sweeps, 50 percent control isn’t very good.”
That bollworms are getting harder and harder to control with pyrethroids is an established fact, Catchot says.
“We came out with a recommendation to add acephate to a pyrethroid, and I still think that’s a solid recommendation. Acephate has pretty good activity on adult moths, even at the half-pound rate. I’ve seen a lot of dead moths behind the half-pound rate, although I don’t know how much it’s going to help on larvae — last year, we had control issues even with that mix.
“One of the things I want to emphasize is that we have good products that will work with this pest. We had good results last year with Belt, a new product, and Steward, which has been around for a long time and has been an anchor in our control programs.
“But it can be expensive to apply these pesticides — price of the product alone can range from $12 to $18 per acre.”
But, Catchot says, growers may be letting dollar signs stand in the way of an effective control program.
“We’ve become so accustomed to pyrethroids being so cheap, we tend to measure every new insecticide by what pyrethroids cost. If you can apply a full rate of a pyrethroid for $2.50, and a new product costs $8 to $10, you think, ‘Oh Lord, I’ll never use that.’
“This year, I’d be thinking about coming out of the gate with these products that we know will work and provide a good residual. We are getting better control, and extended control, with these products.”
Also, Catchot says, tobacco budworm numbers have been increasing in soybeans, “and pyrethroids aren’t going to work on that pest.”