Cutworms (Agrostis spp.)

Cutworm larvae and damage to sunflower seedlings.

Several species of cutworms attack a wide range of vegetable, field and cereal crops in Queensland. Crops should be monitored from emergence through to establishment. "Cutworm" is derived from the larval habit of severing the stems of young seedlings at or near ground level, causing collapse of the plant. Sometimes, the young plant is partially dragged into the soil, where it is fed upon by the larvae. Crop areas attacked by cutworm tend to be patchy, and cutworms may migrate to adjacent areas if food becomes scarce.

Adult cutworms are dull stout-bodied moths with a wingspan of about 4 cm. Small pearly-white eggs are generally laid on soil under low growing weeds, but may sometimes be deposited amongst organic material on the soil surface. One cutworm species prefers moist soil for egg-laying. The larvae, which emerge after a few days, feed at night and rest just beneath the surface during the day in the soil. There are five larval stages, lasting 4-6 weeks, and full grown larvae measure up to 5 cm long. The larvae are hairless with dark heads and usually darkish grey or brown coloured bodies, often with longitudinal lines and/or dark spots, and the skin often has a rough, granular texture. The larvae curl up and remain still if picked up.

Mature larvae stop feeding and pupate in an earthern cell in the top 5 cm of soil, often under an object (such as a piece of wood). Female moths are highly prolific, and can lay up to 2400 eggs. The lifecycle from egg to adult takes about 2 months.

Cereal crops adjacent to permanent vegetation (or fields previously sown to grassy sod or legumes) are prone to cutworm attack, as are crops which possess high weed populations. Consequently, farm practices often have a considerable bearing on cutworm incidence. Good weed management in the weeks before planting is essential.

The degree of control by insecticides depends on a number of factors; including larval size, soil penetrability to sprays, rainfall and the residual life of the chemical used; but usually only one application is needed.

Cutworms are attacked by a wide range of parasites, predators and diseases.

Last Updated March 2004