Cereals: Armyworm (True - Pseudaletia unipuncta, Fall - Spodoptera frugiperda)
Pub 812: Field Crop Protection Guide > Chapter 4: Cereals > Armyworm (True and Fall)
Field Crop Protection Guide 2011-2012, Order 2011-2012 publication
Table of Contents
True 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.
Image 2. Fall armyworm larva damage on corn ear. Larvae leave entry holes on the exterior of ear. Note head is black wih a white, inverted "Y" on the front.
Five to six larvae in a 30 cm x 30 cm area warrant chemical control. Treat if larvae are smaller than 2.0 cm long and threshold has been exceeded. if larvae have white eggs attached to them, they are parasitized and may not require treatment.
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