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Vine Weevil

Garden pest · Otiorhynchus sulcatus

Description​

Vine weevil, also called black vine weevil, is a beetle that damages many garden and container plants, including rhododendrons, heucheras, strawberries and primroses. The adult is a dark, flightless beetle that feeds at night, cutting rounded notches from leaf edges. This damage is conspicuous but usually less serious than the damage caused by its larvae. Females lay eggs near plants, and the young grubs feed in the soil on fine roots. Larger grubs can also chew thicker roots and the base of the stem. Affected plants may grow poorly, wilt despite moist soil, or suddenly collapse, especially in pots where the grubs are concentrated. Adults are most noticeable from spring through autumn; grubs may remain in the soil over winter. Because adults can walk between plants, leaf notches can appear on a plant whose roots are not infested. Checking the roots is important before attributing a plant’s decline to vine weevil.

Symptoms​

  • Holes in leaves
  • Wilting
  • Stunted growth
  • Leaves dropping
  • Insects visible on the plant

How to Identify​

Look for repeated, roughly semicircular notches along leaf edges. After dark, use a flashlight to check leaves and pots for adult beetles: they are about 8–10 mm long, dark and speckled, with a short snout. To confirm the more damaging larval stage, ease a declining plant from its pot or inspect soil around the roots. The grubs are creamy white, legless and C-shaped, with brown heads. Slugs tend to leave irregular damage and often slime trails, rather than neat edge notches. Wilting from drought or root disease can look similar, but finding grubs and chewed roots points to vine weevil.

Prevention​

Inspect new plants, especially container-grown ones, for notched leaves and grubs around the root ball before adding them to the garden. Check susceptible plants regularly at night so adult beetles can be removed before they lay eggs. Keep pots and nearby hiding places under observation, since flightless adults can walk from one container to another. Where practical, isolate newly purchased or suspect pots until you are confident they are clear. Use fresh, clean potting mix when repotting rather than reusing mix from an infested container. Healthy plants tolerate some adult feeding better, so provide suitable watering and growing conditions, while avoiding prolonged waterlogging. Treating grubs promptly in late summer or early autumn can help prevent root damage over winter.

Treatment​

Start by checking plants after dark and picking off adult beetles by hand. For a badly affected potted plant, remove it from its pot, inspect the root ball, pick out grubs and repot in fresh mix if enough healthy roots remain. Dispose of infested old mix without spreading it around other susceptible plants. For grubs in pots or garden soil, apply a biological control containing beneficial nematodes labeled for vine weevil, such as Steinernema kraussei or Heterorhabditis bacteriophora. Follow the product’s temperature and application instructions: nematodes need moist soil, and their effective temperature ranges differ. Late summer to early autumn is often a useful treatment window; a spring application may also be appropriate. Recheck plants because nematodes target grubs, not adults. If damage continues, consider only a pesticide specifically registered for vine weevil on the affected plant, following its label and avoiding harm to pollinators and other wildlife.

Plants Affected​

Choisya, Gaultheria, Heath, Heather, Hebe, Leucothoe, Rhododendron, Skimmia, Taxus, Yew

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