Insect pests may not be as big a threat as diseases to Texas' Southern Plains peanuts but growers should be aware of potential damage and follow a thorough scouting program to prevent economic losses.
“Insects are not as significant in peanuts as in cotton in this area,” says Scott Russell, Extension agent, Integrated Pest Management.
Russell provided an overview of potential insect damage during a recent peanut production seminar in Seminole, Texas.
Early threats, just after planting, include white grubs, wireworms and wild hogs, Russell says. “White grubs can reduce stand counts but are a sporadic problem. Check in several areas of the field and especially in fields adjacent to grain crops.”
Wireworm, the larval stage of the click beetle, causes problems only sporadically and usually following grain crops with heavy infestations. He says Temik should be an adequate control.
“Wild hog is a different kind of pest,” Russell says. “They can smell carbon dioxide coming off emerging seedlings and will go down a row digging up seeds and young plants.”
Controls include hunting and trapping. “You just need a hunting license,” he says. No season restrictions exist for shooting wild hogs. “You can even spotlight them. Just let the game warden know.”
Cracking time pests include root and pod feeding insects such as wireworms and the Southern corn rootworm and foliage feeders including thrips, caterpillars and grasshoppers.
Russell says the rootworm is not a frequent pest. “But last year we saw several fields that needed treatment.”
Thrips “are not a significant pest for peanuts in the Southern Plains. We see no economic return on treating thrips here.”
He says a new species of chili thrips, however, could be trouble. “It's bad on peanuts and is a vector for tomato spotted wilt virus.”
Caterpillars, also sporadic pests, include corn earworm, armyworm, cutworm and clover worms. Russell says a number of fields had to be treated for worms in recent years.
“Scouting is crucial to prevent damage,” he says.
“Grasshoppers are occasional pests in peanuts but we have no specific threshold. Look at the number of nymphs, consider the canopy size and the general health of the plants. If a grower needs to treat, he should apply insecticides when the grasshoppers are young. They are easier to control then and taking them out early may prevent spread to other parts of the field.
“Also remember that peanuts can take considerable defoliation before significant yield loss is likely.”
He says data from 1989 and 1990 indicated a six to eight caterpillar count per foot of row treatment threshold, depending on peanut type. “Now, the cost of treatment is much higher so that threshold goes up. Also, consider the beneficials. Sometimes beneficial insects will eliminate a pest before you need to spray.”
From bloom to harvest, growers should watch for foliage feeders and pod feeders. The lesser cornstalk borer may be the most important pod feeder. “It's usually in the drier fields,” Russell says, “and we often find them in alternate rows where farmers irrigate with drag socks.”
Lesser cornstalk borers feed on underground plant structures. “Tolerance is low,” Russell says, “because of their potential to increase aflatoxin contamination.”
Lorsban 15G is the only product labeled for lesser cornstalk borer control,” he says.
Prime targets include fields with grain the previous year.
“Two-spotted spider mites also may cause trouble late in the season,” he says. They may move in from other crops or weed hosts. “Start looking for spider mites around Sept. 10,” he says. Growers may use several products, including Omite, Comite and Danitol. “Karate may be used for suppression,” Russell says, “but it takes out beneficials.”
Coverage is critical. “You have to get plenty of water into the canopy,” he says. He recommends 15 gallons to 20 gallons of water per acre.
Time to maturity may dictate control strategy. If infestations occur several weeks to a month before maturity and mites are at significant numbers, growers may need to spray.
“If peanuts are only two weeks out and infestation is only over a small area, they might decide not to treat.”