Excessive rain in May slowed moth activity, but we have detected a sudden increase in pest activity across the state. Beet armyworm moths appear to be the most active in vegetable and peanut fields followed by other species like the fall armyworm, southern and the yellowstriped armyworms (the average moth counts is 5 moths per trap and rising). Armyworms typically start out in hay and pasture fields, or feed on weedy hosts before making a move to the row crops. Armyworms typically lay a large number of eggs in several masses on leaf terminals or stems and flowers covered with body scales making them look fuzzy. Colors of these egg masses may vary from grayish to green – eggs darken as they get closer to hatching. Caterpillars hatch and stay clumped together for several days before dispersing – so, the best control of armyworms is when the caterpillars are small and aggregated. Assuming favorable weather conditions, the fall and beet armyworm moth activity expected to increase five times in the next few weeks with peak activity in August in peanuts.
Corn earworm (or tomato fruitworm), cabbage and soybean looper moths have also started to show some activity in crop fields (1 moth average per trap); those moths lay round eggs singly on leaves and fruits. We can expect rapid growth in the activity of loopers as rows crops begin to grow with more foliage. Historically, tobacco budworm activity appears to be higher in some North Alabama locations with mixed populations in the south. Telling apart corn earworm and tobacco budworm larvae can be difficult, so seek help from extension. The lesser cornstalk borer, a major insect of peanuts, has been found in large numbers in insect traps (71 moths average per trap) but the wet weather is keeping the larvae away from crops. Most moths mentioned are night-flying pests when they are most active for mating and egg laying.
Several insecticides are currently available for caterpillar control in peanuts – they broadly range from general nerve toxins (like synthetic pyrethroids and spinosyns belonging to Groups 3 and 5), feeding inhibitors (selective insecticides in Groups 22 and 28), and growth regulators (selective insecticides in Groups 15 and 18). Remember that the newer selective insecticides in general have longer residual, cause minimal nontarget eggects, and are good rotation products with traditional chemistries available for peanut growers. One of the major concerns with insecticide misapplications is the rise in spider mite infestations caused by the reduction in beneficial mites – spider mites can cause significant yield reduction and are tough to battle in peanuts. Overapplication of insecticides may also destroy big-eyed bugs, lady beetle, and lacewing larvae that can result in aphid and whitefly outbreaks. The attached figure shows caterpillar control materials that can be used with the aim of preventing secondary pest outbreaks. Protection of natural enemies is thus a very critical aspect of the farming system. Consult extension agent for correct insect identification and for developing an IPM plan that is cost-effective for your farm. For more details about individual IRAC Insecticide Groups, visit www.irac-online.org. For more insect management information, please visit Alabama Peanut IPM.
Ayanava Majumdar, Extension Entomologist, Alabama Cooperative Extension System/Auburn University
Kris Balkcom, Extension Specialist, Alabama Cooperative Extension System/Auburn University
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