Unlike diseases and weeds — which you can count on with some degree of certainty each year — insects represent the wild card in peanut pest control.
“Insects are more unpredictable than the other pest problems we encounter in peanuts,” says Steve L. Brown, University of Georgia Extension entomologist. “Insects can be really bad or non-existent. Every year is different, and this causes problems because growers can't plan for what'll happen each year.”
When an insect problem does arise in a peanut field, growers many times find themselves scrambling to decide which control option will work best, says Brown.
Producers were forced to deal with several such problems this past year, he adds. “We saw quite a few foliage-feeder problems in 2002. Starting in July, we saw some outbreaks of beet armyworms. The pressure was severe in some areas, and we had a few fields that actually were defoliated by mid-July,” he says.
The insecticide Steward from DuPont was registered at about the same time as the beet armyworm outbreaks, says Brown. “That's about the only currently labeled product that gives us good armyworm control on peanuts. Since then, Tracer from Dow AgroSciences has been labeled.”
With Steward and Tracer both available this year for use on foliage feeders, growers will need to decide the best fit for each of these new products, he says.
“They can be expensive — depending on the rate used — but they'll be good to have when we need them. Tracer is fairly broad spectrum and is effective on a lot of things. It could be a good fit for us in situations where we have mixed populations of several insects at the same time, and that's fairly common,” notes Brown.
There's some cause for concern, he says, about tobacco budworms in peanuts. “It's important in cotton to make a distinction between corn earworms and tobacco budworms. They're similar species, but they may require different control options in cotton. We've never tried to make that distinction in peanuts because it hasn't made much of difference to our growers.
“We know tobacco budworms feed on peanuts, and I'm seeing some signs that perhaps tobacco budworms may be becoming more important in peanuts. This isn't a widespread situation, but we have had a couple of cases of pyrethroid failures, and they turned out to be pyrethroid-resistant tobacco budworms.”
If this trend continues, and growers start to see more tobacco budworms in peanuts, Tracer would be a good control option, says Brown. Tracer has the shortest pre-harvest interval of any product currently on the market, he adds.
“Our growers have had a real problem because they legally couldn't treat for anything two weeks prior to digging. Velvetbean caterpillars — which we usually see late in the season — are easy to kill, but they're voracious feeders. They can strip a peanut field in just a few days.
“In those cases where we had late-season velvetbean caterpillars, we legally couldn't do anything about it. Tracer can help us here because their interval is three days prior to nut harvest, which takes us right up to digging.”
Georgia peanut producers also need to be aware of potential problems with soil-borne insects, says Brown, and tillage practices can affect the severity of these pests.
“We're changing our tillage practices on peanuts, and I believe as a result we'll see differences in soil-borne insect problems. Some problems will be better in minimum-till situations and some will be worse. Minimum-tillage will help us on lesser cornstalk borers, but it could hurt us on wireworms.”
A soil-borne insect that is new to Georgia peanut fields — and is being seen in some minimum-tillage situations — is the burrower bug, says Brown. This insect can do considerable damage, he says, and can affect the quality of the peanuts.
“It's like a miniature stinkbug that burrows into the ground and feeds on pods. It appears to be confined to situations where tillage is being taken out of the system.”
Turning to insect scouting, Brown says the recommendation remains that peanuts be scouted once per week, from flowering to harvest. “Unfortunately, only a small percentage of our acreage is being scouted. It's a time factor with most growers. But we're trying to get growers to consider hiring scouts not only for insect management but also for weed mapping, watching for diseases and collecting data for programs and models such as AU-Pnuts and Irrigator Pro.”