Several species of root weevils are common pests of raspberries. Adults are typically brown to black in color and may have lighter markings on the back. They range in size from 1/5" to 1/3" in length. These beetles cannot fly. Adults cause minor damage to plants by climbing up the canes and chewing ragged notches in the leaf margins. However, the most serious damage is done by the larvae. They are curved, legless, and white or pinkish with darker heads. They are found in the soil, where they feed on the roots. Severe root damage can occur, resulting in wilting and death of plants. Root weevils generally overwinter in the soil as larvae, with adults emerging in spring to early summer. Root weevil adults typically feed at night and spend the day on the ground or on the canes, where they may become a contaminant in harvested berries.

Management Options

Non-Chemical Management

Hand-pick and kill night-feeding adults, when practical.
Cultivate future planting sites in the fall to reduce numbers of overwintering root weevils.
Control weeds in and around plantings. Weeds may serve as other hosts for root weevils.
Apply beneficial nematodes which kill weevil larvae. The nematodes are used as a soil drench in moist soils over 55 degrees F (mid-fall in western Washington). Read and follow the label directions carefully.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Monitor for weevils with flashlight at night to get a fix on weevil activity. Generally, applications will be made to foliage in the spring and early summer. Apply in the evening if possible to avoid bee poisoning and to get better control of the adult weevils that feed at night.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Azamax Botanical Insecticide, Miticide, & Nematicide [Organic]
Active ingredient: azadirachtin | EPA reg no: 71908-1-81268
Bug Buster-O [Organic]
Active ingredient: pyrethrins | EPA reg no: 1021-1771-54705
This list may not include all products registered for this use.

Images

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Caption: Root weevil larval damage Photo by: A.L. Antonelli
Caption: Adult root weevil damage Photo by: E.P. Breakey
Caption: Root weevil larvae Photo by: A.L. Antonelli
Caption: Root weevil adult Photo by: A.L. Antonelli

WSU Extension

Hortsense