Beet Armyworm
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Beet armyworm (Spodoptera exigua) is a light-green and black larva with four pairs of abdominal prolegs and a dark head. There are many fine, white wavy lines along the back and a broader stripe along each side. There is a distinctive dark spot on each side just above the second pair of true legs. Females lay masses of up to 80 eggs under a covering of cottony-white scales. These eggs hatch in 2 to 3 days and the larvae first feed together in a group near the bud if the plant. As they grow, they disperse. After they complete their feeding, the 11⁄4 inch larvae pupate in the soil. Beet armyworm feeding on young tender growth can be very damaging to small transplants. Often fine webbing is produced by smaller larvae near these feeding sites. Older plants can become rapidly defoliated.
Beet armyworm on cabbage leaf
(Photo: UK Vegetable IPM Team, University of Kentucky)
Management:
- Beet armyworm is not as sensitive to the common types of Bt sprays, but those containing Bacillus thuringiensis var aizawai (Bta) are more effective. This pest is highly resistant to pyrethroid sprays (IRAC group 3), so insecticides from others groups need to be selected.
