Pest description and crop damage Adults look like weevils. Larvae are small white grub, 0.08 to 0.16 inch long, with a brown head and no legs. Damage is to the main root; females bore into the base of a stem laying a single egg at the base of stock. Larvae hatch, feeding on tissues of the main stalk, causing injury or death to the central stalk, which usually breaks off. A female lays approximately 100 eggs per season. It is found in eastern Oregon and Idaho. It can infest mint rootstock for export.
No insecticides are registered. However, aphid or looper sprays applied in mid- to late May generally reduce stem borer populations.