How to judge the age of corn armyworm?

Mainly judged by body color and body length. Larvae has a figure-eight black stripe on the top of its head, and its head is brown to reddish brown. 2-3-year-old larvae are yellowish brown to grayish brown or reddish. Larvae over 4 years old are mostly black or grayish black.

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In addition, the degree of harm can also be judged.

The larvae of 1-2 only eat mesophyll to form a skylight, and after the third instar, they are nicked along the leaf edge. When the damage is serious, it eats most of the leaves, leaving only a short midvein.

The body color of larvae changes with age, density and food. Larvae feed on young leaves, and their body color is green to grayish green. When the population density is high, the larvae above the 4th instar are black or grayish black, and the mature larvae are 38 mm long.

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