Northern Corn Rootworm

species: diabrotica longicornis (say)
common names: northern corn rootworm
hosts:
notes:

Agriculture and Agri-Food Canada Insect Identification Sheet No. 54 March 1981

Northern Corn Rootworm

Diabrotica longicornis (Say)

The northern corn rootworm is found in Canada east of the Rocky Mountains wherever corn is grown. It is an important pest of corn and other grassy species.

Injury:

Both the larvae and adult attack corn. The larvae eat the small roots of corn, while larger roots are burrowed into. Because of root damage, corn growth is stunted and plants may fall over after heavy rains. The larvae are also important vectors for the spread of the disease, bacterial wilt. Adult beetles feed on corn silk and pollen, causing damage to the ears as well as ears that do not obtain a full set.

Life History:

Northern corn rootworms overwinter as eggs laid the previous fall in the ground around the roots of corn. The wrinkled, threadlike larvae hatch in May. White with yellow brown heads, they reach a length of 12 mm when full grown. The larvae burrow into corn roots and feed until July, when they pupate in earthen cells. The pupae are soft and white. Adult beetles emerge late in July and in early August. They are yellowish-green to green in color, and range in length from 4 to 6 mm long. They are very active, tumbling out of the flowers or corn silk when disturbed. Eggs are laid in September, with nearly all adult beetles killed by the first hard frost. In Canada, there is a single generation per year.

Pest Management:

Crop rotation will solve the problem of infestation as eggs are laid only in corn fields and the larvae cannot migrate to other fields. If crop rotation aggravates wireworm and white grub problems, other controls may be necessary. Contact your provincial Department of Agriculture for further details.