Vine Weevil

Root-destroying larvae

Vine weevil larvae are the most economically significant garden pest in Britain. The fat, C-shaped white grubs hatch from eggs laid in soil or compost in summer and immediately begin eating roots. In containers, they can sever every root of a plant by autumn — the first sign of attack is often a plant that suddenly wilts and then falls over when touched, the root system completely destroyed. Heuchera, fuchsia, begonia, cyclamen, strawberry, and many other garden favourites are favoured hosts.

All-female reproduction

The vine weevil is parthenogenetic in Britain — the entire British population consists of females that reproduce without males. Each female can lay 300–600 eggs in her lifetime. This absence of sexual reproduction means the population can grow very rapidly, and there is no “bottleneck” of males required to sustain the population.

Nocturnal adults

The adult beetle is dull black with golden-yellow specks on its wing cases and has a distinctive elongated snout (the weevil rostrum). It cannot fly — the wing cases are fused shut. Adults hide in leaf litter and dense ground cover by day and emerge at night to notch the edges of leaves in a characteristic scalloped pattern. Finding this characteristic leaf-edge notching is a reliable early warning of vine weevil presence.

Biological control

The most effective control is a soil-applied nematode (Steinernema kraussei) that parasitises and kills the larvae. Applied in late summer when larvae are young and soil temperatures are above 5°C, this biological control can achieve 90%+ larval mortality in container and border soil.