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Armyworm
? Agriculture Western Australia
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Description
There are four species of armyworm in Western Australia - the common armyworm, the southern armyworm, the inland armyworm and the sugarcane armyworm. Of these, the common armyworm is the most damaging. Moths are stout bodied, grey to cream, with a wingspan of about 40 mm. They fly at night and are strongly attracted to lights. Armyworm caterpillars vary in colour depending on their numbers in a crop. If there are many caterpillars in a crop then they become dark while if the population is low, the caterpillars are much paler. Armyworms are about 40 mm long when fully grown and can be distinguished from cutworms and budworms by their large heads and by three prominent white stripes on the "collar" behind the head. Often the armyworms themselves will not be seen as they feed mainly at night but their droppings, which look like small green "square" hay bales, will be obvious on the ground below the crop canopy. Another indicator that armyworms are present is damage to ryegrass seed heads.
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