Lawn armyworm are caterpillars of night-flying moths which lay their eggs amongst turf leaves.
The caterpillars grow up to 4cm long and range in colour from green to brown, with darker and paler stripes running along their back and sides. Adult moths are brown and attracted to lights at night.
There can be multiple generations of armyworm in a year, with caterpillars being most active during summer and autumn.
Lawn armyworms feed on grass blades during the late afternoon and early evening. In large numbers, armyworm can advance like an army (hence their name), strip the turf foliage and cause rapidly expanding bare patches in lawns.