While insects might be the easier of peanut pest management issues — compared to disease and weed control — producers can make it harder on themselves by infrequent or improper scouting.
“One of the problems that has arisen over the past 10 to 20 years is that we don’t scout peanuts like we did in the 1970s or early 1980s. Some people remember when we used to train scouts on a regular basis every year — men, women, kids — to go out and routinely monitor pests in peanuts just like we do in cotton,” says David Adams, University of Georgia Extension entomologist.
This has changed over time, he adds, and the ultimate goal is to place pest management entirely in the hands of the grower.
“The biggest problem with that is now we have consultants who do it — and they do a fine job — some growers do it on their own, and some growers try and do it on their own even though they don’t have the time.
“They don’t look at their peanuts on a regular enough basis, and many times they miss problems that are developing in the field because they’re not observing closely enough,” says Adams.
The problem, he says, is that one of the easiest things to drop in peanut production during years of potentially low returns is scouting or pest management.
“It happened over a period of several years, and we sort of fell asleep on things,” he says.
Insects are highly variable in how their populations attack peanuts, says Adams. “One year we may have tobacco budworms, another year cutworms, and another we’ll have lesser cornstalk borers. Last year, we had spider mite problems.
Spider mite explosion
“Over the last 30 years, there might have had been five to seven years when we had real spider mite problems in a general sense. But last year, we did not anticipate the problems in fields where we were not observing very closely, and we let spider mites explode on us before we made any attempt to control them,” he says.
Spider mites are fairly small, says Adams, and most anyone under the age of 30 could see one if they turned the leaf upside down. So when you can see spider mites from the highway, you’ve got a problem.
“Last year was probably the exception to the rule. Years ago, cotton actually was killed by spider mites, and spider mites also can kill a peanut plant.
“There are things we should be aware of when dealing with mites, especially in a dry year. If we harrow or mow field borders after layby, then mites will move into the field. And if the field borders have dried up and died, they’ll move to the peanuts because they’re green,” he says.
Treatments with products like Lorsban can exacerbate spider mite problems, says Adams. This doesn’t mean that growers shouldn’t use Lorsban, or that it isn’t effective for other problems.
“But we have to watch those fields in which we use it for potential spider mite, cutworm and other worm problems. We do kill off a lot of the ground-dwelling predators that live in peanuts.”
Growers many times use pyrethroids with their fungicides to knock out three-cornered alfalfa hoppers, says Adams. “A pyrethroid application typically won’t make something else explode in the field.
“But if we use multiple applications of pyrethroids, we have a tendency to cause problems with other insects, especially foliage feeders.”
Pyrethroids do kill thrips, he says, and thrips is a native predator of mites.
“Typically, we don’t have to use a lot of acetates on peanuts, and we should be worried mostly about in-season applications. It kills a lot of insect pests, and it kills a lot of predators.
“It also hangs around for awhile. It’s still a good insecticide, but you should be judicious in how you use it.”
If you make herbicide rescue treatments in the field, it’s important to remember that mites reside on those weeds, says Adams. If you kill a preferred host, then the mites will move into the peanuts, he adds.
A numbers game
“Once mites get into an explosive situation, it’s a numbers game,” he says. “If you kill 90 percent, you still have a problem. You need to get to them early enough that the numbers are fairly low. In those cases, they can be very spotty, on the margins of the field. Generally, we have not treated early enough to knock down the population before they become a problem.”
For most insect pests, peanut producers have good insecticides, and they have an adequate number of insecticides, says Adams.
“But in the case of mites, they’re expensive. And often, if you see a problem develop, it might just be a low-level population. It’s a judgment call on how much money you want to invest, not knowing if the populations will explode.”
Comite is the best product available for spider mites, but it’s expensive, slow-acting and it’ll burn foliage, he says.
Vegetable producers have three or four true miticides, says Adams, but they are not registered for use on peanuts. Danitol is registered for use on peanuts, but it has low-level activity, he adds.
There’s no new information this year on burrower bugs, he says. “We know drought conditions favor the intensity of burrower bugs, so irrigated peanuts will have a benefit over those that are not irrigated. We still know that conventional-tillage and deep turning are the most effective practices to avoid burrower bugs.”
Growers were encouraged 20 or 30 years ago to transition to strip-till production, he says. “Every time we change a practice, we influence something else. Pigweed is a prime example.
“Lorsban has an impact on burrower bugs, but we don’t know how effective it is depending on the population that’s present. In a low-level situation, it might prevent a load of Seg. 2 peanuts.
“But Lorsban is insoluble, and you can’t drive it down very deep into the ground, even with a lot of rain. The resurgence of other pests is also a problem with Lorsban, so you’re really getting more suppression than anything else.”
Through attrition, the University of Georgia has lost its research component in peanut insects, says Adams. “I can see the gap widening, and it’s getting wider as far as the information regarding insect pests, especially these emerging pests like burrower bugs.”