Small grain-Wheat strawworm

Harmolita grandis

Pest description and crop damage Overwinters in straw and emerges in February or March as a shiny, black, wingless insect. Eggs are laid in or near the developing wheat head. The wall of the short stem around the larvae enlarges and hardens to form a gall. Second-generation adults are winged and lay eggs in wheat stems about the time wheat is in boot stage. Larvae develop in the center or in the wall of the stem, which usually shows no external evidence of injury.

Management-cultural control

This insect is throughout most of the Pacific Northwest but has not been a serious pest. Apparently, only wheat is damaged. Adults may lay eggs in barley, oats, and rye, but larvae can complete development only on wheat. Avoid growing wheat within 125 ft of wheat straw or stubble of previous season, because the spring form is wingless and does not migrate any distance. Thoroughly plowing under stubble and clean summer fallow reduce insect populations.

Management-chemical control

Insecticide control is not recommended.