Vine weevil is a very damaging pest to many ornamental plants and to some other fruiting plants like strawberries. The most common species in the UK is the black vine weevil [Otiorhynchus sulcatus]. All the adults are female, eggs are laid in clusters on or in the soil at the plant base. The eggs develop into larvae before turning into a pupae, which the adult emerges from. Vine weevil overwinter as larvae but can sometimes overwinter as adults in mild conditions. The larvae become active in the spring when the soil or compost warms up. It is the larval stage, which is especially damaging to plants. The larvae have a white body and a brown head. They feed on plant roots and can cause considerable damage to plants, often so severely that plants like strawberries and bedding plants maybe killed. Adults will also feed on leaves leaving a distinctive half moon cut shape on the leaf edges. This damage is largely cosmetic and the lethal damge is carried out by the feeding of the Vine weevil larvae.
How to control
Biological control of Vine weevil is possible with the application of nematodes. For outdoor infestations, Vine weevil larvae should be treated first in the spring [ March -May]. Soil temperatures for the spring application should be above 6-8.c to ensure nematode activity. A second application maybe required in the late summer [ August-October ]. Plants grown in heated greenhouses maybe vulnerable to Vine weevil larvae activity all year round, so can be treated with nematodes at any time they are present.
Dragonfli supply two species of nematodes for Vine weevil control, one for the spring when the soil is cooler and one for the summer when there are warmer conditions.