Vine weevil is an insect pest that infests a wide range of ornamental plants and fruits, especially those grown in containers.
Adult vine weevils eat leaves, and the grubs eat roots.
What is vine weevil?
Vine weevil is a beetle that attacks a wide range of plants, both indoors and outdoors, but is especially damaging to plants grown in containers.
It is one of the most widespread, common and devastating garden pests. The adult weevils eat plant leaves during spring and summer, but it is the grubs that cause the most damage over autumn and winter when they feed on plant roots, causing wilting, and often plant death.
Plants growing in pots or other containers, outdoors or under cover, can be severely damaged by vine weevil grubs. Plants growing in the open ground are less susceptible, although the grubs can kill strawberries, primulas, polyanthus, Sedum, Heuchera and young yew plants.
The adult beetles feed on the foliage of many herbaceous plants and shrubs, especially Rhododendron, evergreen Euonymus, Hydrangea, Epimedium, Bergenia, Primula and strawberry.
You may see the following symptoms:
Adult weevils cause irregular-shaped notches in leaf margins during the summer
The plump c-shaped white legless grubs have light brown heads and are up to 10mm (about 3/8in) long. They are likely to be found among the roots. Plants wilt and die during autumn to spring as a result of grubs devouring the roots
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.
Ornamental plants grown in containers can be treated with acetamiprid (e.g. Bug Clear Ultra Vine Weevil Killer) or thiacloprid (e.g. Bayer Provado Vine Weevil Killer 2) as a liquid drench applied to the compost. These insecticides give protection against the grubs for up to two and four months respectively; treatment in mid- to late summer will control the young larvae and prevent damage occurring later in the autumn to spring period. Neither product can be used to treat edible plants or ornamental plants growing in open soil.
Gardeners with vine weevil should keep up their guard because stopping treatment after the apparent disappearance of the pest can allow numbers to build up again.