Gardeners with vine weevil should keep up their guard because stopping control measures after the apparent disappearance of the weevil can allow numbers to build up again.
On mild spring or summer evenings inspect plants and walls by torchlight and pick off the adult weevils. Shake shrubs over an upturned umbrella, newspaper or similar to dislodge and collect more. In greenhouses, look under pots or on the underside of staging benches where the beetles hide during the day.
Trap adults with sticky barriers placed around pots or on greenhouse staging.
Encourage natural enemies. Vine weevils and their grubs are eaten by a variety of predators such as birds, frogs, toads, shrews, hedgehogs and predatory ground beetles.
A biological control for the larvae is available as a microscopic pathogenic nematode (Steinernema kraussei) available from suppliers of biological controls. This is suitable for use in containers and in the open ground. For best results apply in August or early September when the soil temperature or potting media is warm enough for the nematode to be effective (5-20ºC/41-68ºF) and before the vine weevil grubs have grown large enough to cause serious damage.
Another nematode, Heterorhabditis megidis, is also available but is more temperature-dependent (12-20ºC/ 54-68ºF).
Both of these nematodes can give poor results in dry or heavy soils. They work best in lighter soils and open potting composts, such as peat or coir. Nematodes can be used safely on all edible and ornamental plants.
A trap containing nematodes (Steinernema carpocapsae), is also available for controlling adult vine weevil. The traps should be placed on the ground below plants damaged by the weevils during the summer. The adults enter the trap during the day and are infected by the nematodes.
Ornamental plants grown in containers can be treated with acetamiprid (e.g. Bug Clear Ultra Vine Weevil Killer) as a liquid drench applied to the compost. This insecticide gives protection against the grubs for up four months; treatment in mid- to late summer will control the young larvae and prevent damage occurring later in the autumn to spring period. This product cannot be used to treat edible plants or ornamental plants growing in the ground.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Biological control suppliers (Adobe Acrobat pdf document)