It is time to scout crops again and prevent insect outbreaks with timely intervention! Excessive rain in much of May have slowed moth activity, but we have detected a sudden increase in armyworm 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). Armyworms typically start out in hay and pasture fields, or feed on weedy hosts before making a move to the specialty 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 seem to darken as they get closer to hatching. Caterpillars hatch and stay clumped together for several days before dispersing – the best control of armyworms is when the caterpillars are small and aggregated.
Corn earworm, cabbage looper and soybean looper moths have also started to show some activity in vegetable fields (1 moth average per trap); those moths lay round eggs singly on tender leaves and fruits. Caterpillars typically feed on the leaves of vegetable crops first before moving on to fruits where the damage can be irreversible. On fruits, most caterpillar feeding damage causes fine round holes that may or may not close depending on the development stage of the fruit. Most moths mentioned are night-flying pests when they are most active for mating and egg laying; however, there are other insects like squash vine borers and cabbage butterflies that are major vegetable pests active during the day.
Always start out with moth or caterpillar prevention strategies for your farm or garden. Having healthy plants, timely planting, and using pest exclusion systems are helpful pest preventions strategies. Several insecticides are also available for caterpillar control – they broadly range from general nerve toxins (like synthetic pyrethroids belonging to Group 3 insecticides), feeding inhibitors (Group 22 and 25 insecticides), and growth regulators (selective insecticides in Groups 15 and 18). Remember that selective insecticides belonging to the newer generation of insecticides do minimal environmental harm. One of the major concerns with insecticide misapplications is the rise in spider mite infestations due to reduction in the number of beneficial mites. Insecticides also destroy immature lady beetles and lacewings that may result in outbreak of other pest species like aphids and whiteflies. 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 suitable to your farm. For more details about individual IRAC Insecticide Groups, visit www.irac-online.org. For IPM training videos and toolkits, please visit Alabama Vegetable IPM.
If you wish to see statewide moth numbers from Alabama, then please download Moth Activity Updates 6-25-18.
Ayanava Majumdar, Extension Entomologist and
State SARE Program Coordinator, Auburn University
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