Scouting fields with a sweep net is the best practice to locate fall armyworm infestations early in their life cycle. It takes about 355 degree-days above this lower temperature threshold for the caterpillars to develop from hatching until they pupate.įigure 8. Caterpillars can develop whenever the temperature is above 55 degrees F. Development of all stages of the fall armyworm is driven by temperature, so as temperatures cool in autumn it will take longer for the caterpillars to develop.
7) Under summer conditions, caterpillars feed for about 14 days and most of the feeding is done in the last four days after the caterpillar molts into its largest size. On the next-to-last segment, these spots are arranged like the corner points of a square (fig. There are usually small dark spots on the top side of each segment of the body. Sometimes these lines extend along the length of the caterpillar, as seen in figure 4. Just behind the head, on the back of the caterpillar, you will see three thin white stripes running the length of the next segment. The “face” is marked with a light-colored inverted Y. When fully grown, larvae may be up to 11⁄2 inches long and vary in color from light green to almost black with several stripes along the body (fig. As they grow, their bodies darken and noticeable stripes appear. The tiny, light-colored, black- headed larvae spin down to the ground on silken webs and begin to feed. All the eggs within a mass hatch at about the same time.
These masses darken with age, and the eggs hatch within 2 to 4 days. The eggs are light gray and covered with grayish fuzz from the female’s body. Most eggs are laid 4 to 9 days after the female emerges from the pupal stage. They will also lay eggs on the grass itself. They prefer to lay eggs on light- colored surfaces such as fence rails, tree trunks, and the underside of tree limbs.
The female moths lay eggs at night in masses of several hundred.
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