Beet Webworm

Beet Webworm


(Loxostege sticticalis), a moth of the family Pyralididae, destructive of wild and cultivated plants. Wingspan, 18-26 mm; the grayish brown forewings have darker spots and a yellowish band on the outer edge, and the hindwings are brownish gray with two parallel stripes, which are sometimes poorly defined.

The caterpillar is up to 35 mm long and greenish gray with a gray stripe down the back and several stripes on the sides. The caterpillar hibernates in upper soil layers in a spun cocoon and forms a pupa in the soil in the spring. The moth appears in spring when temperatures reach about 15°C, laying up to 600 eggs on plants. The beet webworm produces one to four generations annually, depending on latitude and weather conditions. The moth is found over a wide range that excludes only the far north; in the USSR it inhabits the steppes and the forested steppe zone.

The beet webworm damages plants belonging to 35 different families; cultivated host crops include sugar beets, hemp, sun-flowers, corn, and many vegetables. The greatest damage is caused by the caterpillars, which feed on the surface parts of the plants. In search of food they can travel in great numbers from one planting to another.

Countermeasures include autumn plowing, harrowing of plowed crops to destroy eggs and caterpillars, and use of insecticide at the appearance of caterpillars. Setting chalcid flies of Trichogramma, loose in fields (10,000 per hectare) to eat web-worm eggs is another effective counter measure.