Cutworm

Photo of cutworm larvae on the soil surface

Cutworm larvae on the soil surface. Photo courtesy of J Wessels.

General information

Several species of cutworms, including  Agrostis munda (brown cutworm), infusa (Bogong moth), ipsilon (black cutworm and prophyricollis (variable cutworm) attack a wide range of crops in Queensland. The common name of cutworm is derived from the larval habit of severing the stems of young seedlings at or near ground level, causing the collapse of the plant.

Scientific name

Agrotis spp.

Description

Larvae are up to 50 mm long, hairless with dark heads and usually darkish coloured bodies, often with longitudinal lines and/or dark spots. Larvae curl up and remain still if picked up. Moths are a dull brown-black colour.

Similar species

May be confused with armyworms and helicoverpa larvae.

Crops attacked

All field crops. Crops are at most risk during seedling and early vegetative stages.

Damage

Young caterpillars climb plants and skeletonise the leaves or eat small holes. The older larvae may also climb to browse or cut off leaves, but commonly cut through stems at ground level and feed on the top growth of felled plants. Caterpillars that are almost fully grown often remain underground and chew into plants at or below ground level. They usually feed in the late afternoon or at night. By day they hide under debris or in the soil.

Monitoring and action level

Inspect crop twice weekly in seedling and early vegetative stage. Larvae feed late afternoons and evenings.

Chemical control is warranted when there is a rapidly increasing area or proportion of crop damage.

Life cycle

Usually a single generation during early vegetative stages. Moths prefer to lay their eggs in soil in lightly vegetated (e.g. a weedy fallow) or bare areas. Early autumn egg-laying results in most damage to young cereals. Larvae hatch and feed on host plants right through to maturity. Mature larvae pupate in the soil. Under favourable conditions, the duration from egg-lay to adult emergence is 8-11 weeks, depending on the species.

Control

Chemical control: Insecticide application is cost-effective. The whole crop may not need to be sprayed if distribution is patchy; spot spraying may suffice. See Pest Genie or APVMA for current control options.

Cultural control: Control weeds 3-4 weeks prior to sowing.

Natural enemies: Cutworms are attacked by a number of predators, parasites and diseases.

Pest status

Minor, widespread, irregular.

Further information

  • Crop Insects: The Ute Guide Northern Grain Belt
  • Pests of Field Crops and Pastures: Identification and Control. Editor: PT Bailey

Last updated 10 February 2010