Vine weevil

Vine weevil is an insect that can infest 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. This damage often results in wilting and plant death.

Plants growing in pots and containers, outdoors or under cover, are most likely to be severely damaged by vine weevil grubs. Plants growing in the open ground are less likely to be damaged, although heavy infestations of grubs can occur on strawberries, Primula, 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, BergeniaPrimula and strawberry. Adults rarely cause enough damage to affect the vigour of plants.

There are several other species of weevil closely related to vine weevil, the adults of which cause similar damage but are less problematic as larvae.

Symptoms

You may see the following symptoms:

  • Adult weevils are approximately 9mm (about 5/16in) long and dull black with dirty yellow mark on the wing cases. They cause irregular-shaped notches of 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

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.

Cultural

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

A biological control for the larvae is available as a microscopic pathogenic nematode (Steinernema kraussei) available from suppliers of biological controls. For best results 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 often 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

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.

Downloads

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

Biological control suppliers (Adobe Acrobat pdf document)

Biology

Adult vine weevils cause notch like  leaf damage, which can be unsightly but rarely affects plant 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 which can cause similar damage to foliage as adults. 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 to 10mm (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. 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 several hundred eggs during spring and summer. The eggs are brown and less than 1mm (about 1/16in) in diameter, making them very difficult to see in 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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    • GaryMartyn avatar

      By GaryMartyn on 15/10/2014

      Could this be responsible for the sudden demise of a potted Acer? Had one suddenly die off last year and blamed the dog!! Had almost no root left. Looks as though I have another this year. No colour change, leaves just browned and appears to be dying.


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    • anonymous avatar

      By anonymous on 29/07/2014

      Hi Andy, chlorosis is common for Hydrangea or at least where I'm from and it shows decreased amount of chlorophyll which is caused by luck of iron in the soil. What we usually do is to add " green stone" = iron chelate for increasing the level of iron. The same effect would have any iron pins, nails that will rust, splashed around the roots like a kind of mulch. Also, you can change the color of your plants by adding or subtracting aluminum. You are lucky, the weevils are not your Hydrangeas' problem. I can not get rid of mine in an eco way and they destroy my fuchsia. Hope this helps, Antoaneta


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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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