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Forages: Armyworm (True - Pseudaletia unipuncta, Fall - Spodoptera frugiperda)
Excerpt from Chapter 4, Field Crop Protection Guide, Order this publication Table of ContentsDescriptionTrue armyworms, full grown, are 4-cm (1 1/2-in.) dull-green to brown larvae that can be easily confused with other caterpillars, including variegated cutworm and fall armyworm. Two distinguishing features that true armyworm possess are white-bordered stripes running laterally along the body and dark diagonal bands at the top of each abdominal proleg. The head is yellow-brown with a network of dark brown lines creating a pattern. The adult sand-coloured moth has distinctive white spots on the centre of each forewing. 
Image 1. True armyworm larvae have black bands at the top of each proleg and the lighter brown head. Full-grown fall armyworms are 4 cm (1 1/2 in.) long, varying in colour from light tan or green to near-black. Three white, thin stripes run down the back with one thicker, yellow band with red spots running along the side, just above the legs of the larvae. Scattered along the body are black spots called tubercles that have spines coming from them.
| Top of Page | Integrated Pest Management OptionsIf 50% of the plants are infested with unparasitized larvae smaller than 2.5 cm (1 in.), insecticide may be warranted. If larvae have white eggs attached to them, they are parasitized and may not need treatment. If the larvae are almost full grown (about 4 cm or 11?2 in. long), there is no benefit in applying insecticide since most of the feeding damage has already been done.
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