![]() ![]() Several larvae may be found on a single ear, because these caterpillars (unlike corn earworm) are not cannibalistic. Entry holes and/or frass are not always visible, so scouting for larvae must include removing husks. There are 6 larval instars, the 6th is most conspicuous and often found feeding on mature ears, usually the tip but sometimes the sides. 4th-instar and larger larvae, ½ to 1-1/2 inches long, are readily identified by 2 black “rectangles” behind the now-orange head, and a generally smooth skin or cuticle (i.e. Newly-hatched larvae are initially dark with black heads, this color will lighten to a light tan or pinkish hue with subtle longitudinal stripes as they develop further. Larvae will then move into protected areas of the corn plant, feeding on leaf tissue, fallen anthers/pollen and silks on their way to their destination, the developing ear. In about a week, eggs develop a purple coloration, indicating that hatch is imminent.įollowing emergence, first-instar larvae will consume their eggshells, making post-hatch scouting for empty masses impossible. Eggs are white when first laid, and become tan as eggs begin to develop. ![]() Eggs are laid in masses of 20-200, but usually average around 50. Eggs will be laid on upper surfaces of leaves, often on leaves near the whorl that have not unfolded completely and vertical in orientation. Cornfields in the late whorl stage are preferred by female moths, who are seeking to lay eggs on corn that is near (but not past) pollination. Female moths will mate and lay eggs during July and August and will oviposit on a variety of cultivated and wild plants, although dryland beans and field corn are the most commonly chosen oviposition sites. Moth emergence begins in early July and usually peaks in the middle of the month, when male moths can be monitored using pheromone traps. Other identifying marks are a circular spot approximately halfway along the length of the forewing and a kidney-shaped mark along the same line, approximately 2/3 of the way to the wingtip. The primary identifying characteristics are a whitish stripe at the front of the forewing with two cream-colored, outlined shapes immediately behind. Moths are primarily grayish-brown in color with a wing-span of approximately 1-1/2". The western bean cutworm is a late-season pest and its feeding can cause both yield loss and degrade quality of grain. It is not a true “cutworm” in that it feeds on the reproductive parts of the plants, and not by cutting stems as many cutworms do. Although primarily known a pest of field corn in many areas, its broad host range also includes legumes and it can be a pest of dryland beans (but not soybeans), where they are grown in abundance. Following its initial discovery in southeastern Iowa in 2004, it was found the following year in western Illinois and in northwestern Indiana in 2006. ![]() The Western Bean Cutworm is a native of North America that has recently expanded its range eastward from the Great Plains region. ![]()
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