Insect problems increasing in Southeastern peanuts

Not too long ago, many peanut producers in the lower Southeast could limit their insecticide applications each year to a single in-furrow treatment for thrips. But that’s no longer the case.

More recently, says University of Georgia Extension Peanut Specialist John Beasley, other insect problems have required producers to make several insecticide applications in a season. “In order to maximize profit potential, we need to stay on top of any potential outbreaks of insects. If an insect reaches populations that exceed the economic threshold, there is a very good chance yield and profit potential are being compromised,” he says.

There’s no need, says Beasley, to hire a pest management scout if you’re willing to scout your fields on a weekly basis. “If you don’t have time to scout your fields weekly, then consider hiring someone. Your local county Extension agent can provide information on the proper scouting techniques. Staying ahead of potential insect outbreaks may make a difference between making a profit or losing money,” he says.

This past year, Georgia growers saw an outbreak of tobacco budworms. The tobacco budworm is closely related to and similar to the corn earworm but much more difficult to control.

“I talked with several retired entomologists with experience dating back to the 1950s, and none of them could remember a year in which we had an outbreak of tobacco budworm at the levels we saw in 2008. There is usually a mix of corn earworms and tobacco budworms in a population, with corn earworms dominating,” says Beasley.

The trouble with tobacco budworms was that the pyrethroids were not effective in taking out the entire population, he says. Many producers were forced to make several insecticide applications to control the pest, and this ate into their profit potential, he adds.

Last year, there was one report of a peanut field that had up to 80 to 90 tobacco budworms per foot of row, says Beasley. “It took seven insecticide applications to bring them under control. Our normal economic threshold for foliage-feeding insects is four per foot or row or up to eight per foot of row in healthy, lush vines. It was not unusual for some fields to have been sprayed three to four time to get the budworms under control,” he says.

During the past three to five years, Georgia peanut producers have also had outbreaks of granulate cutworms, burrower bugs and three-cornered alfalfa hoppers. “Each of these can significantly cut into yield and profit potential if left unchecked,” says Beasley.

In Alabama, peanut growers continue to have problems with cutworms in some areas, says Ron Weeks, Auburn University Extension entomologist.

“We see fairly high populations in some fields, but it seems to be isolated incidences. We’re seeing higher numbers of worms and we’re having more difficulty controlling them. The pyrethroids don’t work as wells as they once did, so we’re basically having to switch over and use Steward, Tracer and Lannate.

“Last year, we ran out of Tracer and started using Steward where we ran into problems with cutworms. Even then, in high populations, we were controlling only half the worms. In some cases, it took a couple of applications to control cutworms,” says Weeks.

Velvetbean caterpillars are usually easy to control in peanuts, but some growers in isolated areas are still having problems controlling this pest, he says. “Again, the pyrethroids don’t seem to be working very well. Other materials like Tracer, Steward and these higher priced insecticides do seem to work very well,” he says.

Alabama growers continue to see high numbers of spider mites, leafhoppers and three-cornered alfalfa hoppers, says Weeks. “In the past couple of years, we’ve especially seen higher numbers of three-cornered alfalfa hoppers. We still don’t have a real good handle on threshold levels for this pest. We spent a lot of time spraying for them two years ago and it didn’t seem to do much good. We caused a lot more problems with foliage feeders and spider mites. We’re not convinced yet that we need to be spraying a lot for three-cornered alfalfa hoppers.

“In certain situations, they can make peanuts look awfully ugly. We do have a limited amount of data that shows we can have a reduction in yield of 300 or 400 pounds per acre if you have particularly high populations of this pest. But I’m not sure it’s a good tradeoff if you have to spray foliage feeders three or four times, and you end up having spider mites later in the year,” he says.

Soil insects also continue to be a concern for Alabama producers, says Weeks. They can cause a lot of damage and yield loss in peanuts, in addition to significant quality losses.

“We still have only one active ingredient we can use in peanuts to control soil insects and that’s chlorpyrifos or Lorsban, or the generic materials. We can only use and incorporate it preplant for pests like white grubs and wireworms. For in-season damage from pests such as lesser cornstalk borers and burrowing bugs, we can apply it as a banded application over the row when scouting reveals greater than 30-percent pod damage,” he says.

Burrowing bugs have been a problem for Alabama producers during the past couple of years, says Weeks. “We’ve seen growers who make 5,000-pound per-acre peanuts only to see them go Seg. 2 due to quality problems. They don’t always cause a lot of destruction in yields. Their damage is concealed. We’ve especially seen problems with this pest in strip-till, high-organic situations where a lot of residue is present. Dry weather also enhances the problem.”

Thrips are an annual problem on peanuts in Alabama, says Weeks, and they are particularly important because they vector tomato spotted wilt virus.

“In the last couple of years, the Southeast has seen less incidence of tomato spotted wilt virus than in some previous years. But since we’re not sure if this will continue in the future, we need to continue taking precautions, including planting some of the newer varieties that are more resistant to the disease. If we have a heavy virus year and we’ve planted a susceptible variety, we could have a significant loss at the end of the growing season,” he says.

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TAGS: Peanuts
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