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Section 26.6.10: Fall Armyworm

Spodoptera frugiperda

Time of concern: Mid-July through September
Key characteristics: Spherical eggs are laid in masses of 100 or more at random locations throughout the plant. Egg masses are covered with moth body hairs, giving them a fuzzy gray appearance. The adult moth has a 1 1/2 inch wingspan. When full grown, larvae are tan, green, or very dark and reach a length of 1 1/2 inches. The front of the head has an inverted, white Y. Because eggs are laid in masses, larval infestations are spotty.  FAW feeding is characterized by large, ragged holes and frass pellets that resemble coarse sawdust. 

Management Option Guideline

Processing sweet corn - FAW is a pest that annually immigrates from the south. Use a pheromone trapping system to monitor the flight activities of the adult moths. See References 10 and 13. Generally, the FAW is not a marketing concern for processing sweet corn. If the fall armyworm is a marketing concern, follow the protocols described for fresh-market sweet corn below. See Reference 4.

Fresh-market sweet corn - Scout for FAW damage and larvae when scouting for other pests. Sample fields once per week, more often if the temperature is above 80°F. Use the sampling protocol in fields of ten acres or less. If fields are larger, divide them into ten acre blocks and sample each separately.

Growth Stage Threshold
Early tassel and tassel 15% infestation
Silk stage through harvest 5% infestation in ear zone

Females are generally attracted to whorl stage corn for egg-laying, but later in the season when whorl stage corn is not available, and FAW adult populations are high, larvae will infest the ear tips. A fact sheet from Massachusetts suggests treating silk stage corn every 5-7 days if weekly FAW trap catches are higher than 10 per week. The most recent trap catches of the Sweet Corn Pheromone Trap Network are posted and updated each Tuesday during the growing season.

Natural enemies

A variety of natural enemies help suppress FAW infestations including predators, parasitoids, and pathogens. Use Natural Enemies of Vegetable Insect Pests for identification of natural enemies.

NOTE: Predators can substantially reduce the number of FAW eggs. To maximize the effects of these biological agents, use insecticides that will conserve natural enemies. Bt varieties have been effective against FAW while conserving natural enemies.

Resistant varieties The only highly resistant varieties available are Bt sweet corn varieties.  Single Bt gene varieties have provided excellent control of European corn borer (ECB) and good control of corn earworm (CEW) and FAW under typical insect pressure.  Under high pressure, supplemental insecticide sprays for CEW and FAW may be warranted for single gene Bt sweet corn varieties.  Dual Bt gene sweet corn has provided excellent control of ECB, CEW and FAW.
Site selection/planting If feasible, plant early and thereby harvest before the arrival of migrant FAWs.
Insecticide Resistance Management

The Insecticide Resistance Action Committee (IRAC) has classified insecticides into resistance management groups. Most insecticides include an IRAC group number on the front page of the label. Alternating between insecticides with different group numbers will help avoid the development of resistant insect populations.

Crop rotation,
Postharvest, and
These are not currently viable management options.
Pesticides Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production