Pest description and crop damage The woods weevil is a native insect and is also known as the raspberry bud weevil. The adults are sooty dark brown, covered with small hairs and with gray spots or patches on posterior end; about 6 mm long. The larvae are stout, legless grubs with pale brownish markings on their posterior ends. Unlike most root weevil larvae, which assume a "C" shape, woods weevil larvae are often straight. Adults feed on the buds of raspberries while larvae feed on the root system.
Biology and life history All life stages of this weevil may be present throughout the year. However, a flush of adults appears in late summer, often following fall rains. They may continue to feed throughout the winter as temperatures allow.
- beneficial nematodes-Heterorhabditis spp. and Steinernema spp., have shown some effectiveness in controlling larvae when applied as label directs, as a drench in the fall. Nematodes must be placed in the root zone where weevil larvae are.
Management-chemical control: HOME USE
There are no products registered for control of this pest.
Management- chemical control: COMMERCIAL USE
Apply foliar sprays at night, usually between dusk and midnight, on warm, calm evenings when adult weevils are on foliage and feeding. Control is usually poor when applied by day or on cold or windy nights.
- Beauveria bassiana (Mycotrol and other brands)-Consult label for rate. Some formulations are OMRI-listed for organic use.
- esfenvalerate (Asana XL) at 0.05 lb ai/a. PHI 7 days. Label allows use for weevil control in Oregon and Washington only. Asana can act as a bee repellent; do not apply within 7 days of pollination. Apply as a pre-bloom or post-bloom spray only. Remove bees prior to application. For maximum safety to bees, apply in the evening after sunset. Because of pollinator hazard, WSU entomologists do not recommend its use on red raspberries. Restricted use pesticide.
- malathion (several brands)-Check label for rate. PHI 1 day. EC formulations may leave an oil film on fruit when used near or during harvest. Apply only in late evening to protect bees at bloom.