True Armyworm

042913_2028_HaveILostAn2There have been reports of Armyworm sightings in local wheat fields.  If you are concerned or locate armyworm, here is some information to help you determine thresholds, manage the pest and protect your crops. 



True armyworms (also known as common armyworm), when full grown, are 4 cm (1 1/2 in.) long. The dull-green to brown larvae can easily be confused with other caterpillars, including variegated cutworm and fall armyworm. Two distinguishing features of true armyworm 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 mottled pattern. The adult sand-coloured moth has distinctive white spots on the centre of each fore wing.

Life History:

True armyworms over-winter as partially grown larvae. In early spring, the moths emerge and prefer to lay their eggs in grassy vegetation, including cereals, grassy forages and rye cover crop. Larvae hatch from the eggs and feed at night or on overcast days for approximately a month. There are two generations per year, but it is the first generation that tends to do the most damage to corn in Ontario. Outbreak years tend to coincide with cool wet springs that are detrimental to the parasites that typically control armyworm.


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