Vine weevil

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.

An adult wine weevil feeding on a rhododendron

Quick facts

Common name Vine weevil
Scientific name Otiorhynchus sulcatus
Plants affected Ornamental plants and fruits, especially those grown in containers
Main symptoms Adult weevils notch leaf margins; grubs eat roots, causing plant death.
Most active Adult weevils: spring to late summer; grubs: summer to spring

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.

Symptoms

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

Control

Cultural Control

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.

Biological Control

A biological control of the larvae is available as a microscopic pathogenic nematode (Steinernema kraussei) available from suppliers of biological controls. Apply in August or early September when the soil temperature 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 nematodes can also be applied to garden soil, but give poor results in dry or heavy soils. They work best in open potting composts, such as peat or coir. Nematodes can be used safely on all edible and ornamental plants.

Chemical control

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.

Downloads

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biological control suppliers (Adobe Acrobat pdf document)

Biology

Adult vine weevils are responsible for leaf damage, which can be unsightly but rarely affects the plant's growth. The adults are 9mm (about 5/16in) long, dull black beetles with a pear-shaped body when viewed from above. Adult weevils may be seen on the foliage at night; during the day they hide in dark places. They are slow-moving insects that cannot fly but they are excellent crawlers and climbers. There are several other related species found in Britain. Some that have recently become established include Otiorhynchus armadillo, O. crataegi and O. salicicola, cause similar damage to foliage.

Far more serious is the damage caused by the soil-dwelling larvae, which are plump, white, legless grubs up to10mm (about 3/8in) long with pale brown heads. These eat the roots of a wide range of plants and can bore into tubers of cyclamen and begonia, and into stem bases of cacti and succulents , devastating many pot plants. They can kill woody plants by gnawing away the outer tissues of the larger roots and stem bases.  Most plant losses occur during September to March, when the grubs are becoming fully grown.

All Otiorhynchus sulcatus adults are female and each can lay many hundreds of eggs over a period of several months from April to September. The eggs are brown and less than 1mm (about 1/16in) in diameter, making them very difficult to see in the soil. Larger yellowish-brown spherical objects seen in potting composts are likely to be controlled-release fertiliser pellets added by the nursery that raised the plants.

    Vine weevil larvae, showing their small brown heads and C-shaped, legless bodiesVine weevil pupae close to developing into adultsVine weevil grubs feeding on cyclamen tuberRhododendron leaves showing typical adult vine weevil notching around the margins

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    • Andy Trayford avatar

      By Andy Trayford on 19/05/2014

      Hi, not sure if my Hydrangea has vine weevil but the leaves are turning yellow, or rather their are losing their green-ness. I have 4 hydrangeas together and only 1 is affected - the largest one. Any clues as to what it could be? I did give them all a dose of Hyrdangea feed about 2 months ago. Could it be that the feed was too strong for that particular one, or that it received moire than the advised dosage?

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