What is in this article?:
- Scouting for soil insects in peanuts pays dividends
- Chemical control
• In Alabama’s peanut insect monitoring project for 2009-2010, more than 25,000 insects were trapped and more than 400 pounds of soil analyzed.
• Insects are attracted to peanut pods because the pods give off carbon dioxide and heat.
For chemical control, a granular insecticide can be applied early in the season, at pegging, he says.
Southern corn rootworms were not seen much throughout Alabama in 2010, with the exception being in Lee County in east Alabama. Larvae make one or more holes on the side walls of a peanut pod in order to access the kernels. Soils with high organic matter and those that hold moisture, such as clay soils, have been associated with infestations in peanut fields, probably due to increased survival of the immature stages under those conditions.
“Another peanut insect pest, wireworms, makes large entry holes in the pods to feed on the seeds. Pod injury symptoms from wireworms can look like Southern corn rootworm injury, but wireworms are known to make larger injury holes on the pods than rootworms.”
For scouting wireworms, Majumdar suggests first studying the field history to see if there were previous infestations. Then, use germinating seed baits in the soil. “Seed baits should be used before planting peanuts, and the accuracy of seed baits improves with the number of baits. An economic threshold would be one wireworm per bait station or 30-percent pod damage.”
Minor soil insect pests of peanuts include white fringed beetles and cutworms, he says. The larvae of white fringed beetles make irregular holes in the taproot, proving fatal to peanuts. This insect pest looks like a boll weevil, he adds, but has no snout. The adult has white stripes on its side, and the larvae are plump with a reduced head.
Cutworms can be found throughout Alabama, says Majumdar, with more than 60 crops and turf playing host to the insect. They are greasy, plump caterpillars, and the larvae curl when touched.
Cutworms cut seedlings at night and may climb plants, he says. Granulate cutworms bore into the middle of the peanut pod, leaving a large hole.
Cutworms often are detected whenever a grower is scouting for other insects. The risk is higher in dry conditions and well-drained soils.
Majumdar (Dr. A) can be reached at (251) 331-8416 or firstname.lastname@example.org.