Crop Insects




Agrotis spp.



Cutworm larvae (Agrotis spp.)
? Agriculture Western Australia

There are several species (Agrotis infusa, A. munda, various other species) in this State which vary in appearance but the larvae are all smooth and plump. The larva of the most common species, the pink cutworm, is grey-green with a pink tinge and is usually found in sandy soils. The larva of another common species, the bogong moth, is dark grey. The larvae usually hide by day but may be found under the surface and often close to a damaged plant. They curl up when disturbed. At times, brown cutworms with a herringbone pattern along the back, damage crops. In south coastal areas they are more likely to be found on the soil surface by day, than are the pink or black cutworm. The adult moths of herringbone cutworm are of various species, and range from black, through grey to brown. Occasionally, autumn attack by armyworm in cereals resembles cutworm damage. This is significant, because armyworm are harder to kill with insecticides than are cutworm.


Cutworm moth
? Agriculture Western Australia

Life cycle
Eggs are laid on the soil or on plant material close to the ground. The larva may grow 50 mm long before becoming a pupa and then the adult moth. The adults are stout-bodied, with a wing span of up to 40 mm. The forewings are patterned brown or dark grey. Several generations are possible in one season.

Damage to cereal seedlings
? Agriculture Western Australia

As the name implies, the cutworm chews through plant parts, often felling the plant at ground level. Just two or three large caterpillars would seriously damage a square metre of crop and almost all crop and pasture plants are susceptible to attack. This is not a regular pest but large areas may be affected.
The weather and food supply are the most important factors in determining abundance. Biological control, such as by fungal diseases, may be spectacularly successful, while wasp and fly parasites are also very active in preventing more frequent and serious outbreaks.