Newly hatched larvae are about 5 mm long with six legs, white bodies and pale brown heads. Fully grown larvae are 25-30 mm in length with a creamy-white body and light brown head. The rear end has a dark grey tinge, when resting the grubs curl into a C-shape. The adult beetle is a rich chestnut colour when newly emerged, but changes to a shiny black, stout bodied beetle approximately 10-15 mm long.
Native to Africa, now present in Australia and the northern island of New Zealand. In Australia it occurs mainly in south-western Western Australia and from the coastal south-eastern mainland up to South East Queensland. It is not recorded in Tasmania.
A major pest in southern Australian maize, but not recorded as a pest in Queensland. It has a widespread distribution in winter rainfall areas. Its occurrence is irregular, but an outbreak may occur several years in succession in the same location.
Spring and early summer. Dry springs and summer favour build-up in numbers.
Most damage is caused by adults feeding on the underground stems of young plants, often killing growing points so that the central shoots wither and the plants become dead-hearted. Older plants usually survive, but remain weak and liable to lodging.
Beetles may be present in the soil prior to planting, especially if the land has recently grown pasture. Soil sampling will indicate the presence of beetles. Beetles may fly in after planting. Beetles are often found near the base of damaged plants. Damaged young plants usually produce suckers.
Beetle numbers in excess of 10 per square metre may result in significant crop damage, but control may be warranted with densities of five per square metre or less.
Chemical control should aim at preventing beetles feeding on young plants. Chemicals should be applied at planting in the furrow or as a surface band if numbers are less than five per square metre.
Cultural control: avoid planting into recently cultivated pasture that may contain adults. Removal of grass and weeds from headlands removes potential reservoirs. Beetles crawling into a crop can be stopped by cutting a deep furrow with a vertical side nearest the crop. Beetles that concentrate in the furrow can be killed. Sowing delayed until November-December when most beetles have died, but before the new generation of beetles emerges in January, may avoid most beetle activity
Pests of field crops and pastures: identification and control. Editor: P.T. Bailey