Vine Weevil Is Killing My Strawberry Plants

Strawberry plants that suddenly wilt and collapse in late summer or autumn — despite adequate water and no visible above-ground problem — and when pulled reveal plump, white, C-shaped grubs in the soil around the roots, have vine weevil (Otiorhynchus sulcatus) larvae. Vine weevil is one of the most destructive soil pests for strawberries, particularly those grown in containers, and its larvae can kill an entire pot of plants in a matter of weeks. Recognising the signs early and understanding the lifecycle is essential for management.

Identifying vine weevil

The larvae are 8–12 mm long, creamy-white with a brown head capsule, and curl into a characteristic C-shape when disturbed. They are found in the soil and compost around roots, eating the root system from below. The adult vine weevil is a dull black or dark grey beetle (about 9 mm) with a distinctive long "snout" and elbowed antennae. Adults are nocturnal and leave characteristic U-shaped notches along the edges of leaves — this notching is usually the first visible symptom of vine weevil presence, appearing in late spring and summer when adults are active. Larvae do their damage from late summer through winter.

The lifecycle

Adult vine weevils lay eggs in compost or soil from June to August. Eggs hatch into larvae that feed on roots from late summer onward, reaching their most damaging size in autumn and winter. This is why strawberry plants often appear to collapse suddenly in September or October — by that point the larvae are large and have consumed much of the root system. The lifecycle means the window for effective nematode application is late August to early October, when larvae are young and the soil is still warm enough for nematode activity.

Biological control with nematodes

Steinernema kraussei nematodes (available as a proprietary product from garden suppliers) are highly effective against vine weevil larvae when applied correctly. They must be applied to moist, warm soil (above 5°C) between August and October. Water them thoroughly into the compost of container plants and the soil of bed-grown plants. Results are excellent when timing and soil temperature are correct. This is the most reliable control for organic growers and avoids the use of chemical insecticides.

Physical measures

A ring of copper tape around container rims deters adult vine weevils from climbing in to lay eggs — not foolproof but a useful complement to nematodes. Inspect container plants by tipping them out in autumn and removing any larvae found in the root ball before repotting in fresh compost. Use fresh compost when replanting strawberries.