Why Are My Grapevine Leaves Notched at the Edges?

Grapevine leaves with characteristic scalloped or U-shaped notches cut from their margins — as though someone has been at them with a small hole punch — are a tell-tale sign of adult vine weevil (Otiorhynchus sulcatus) feeding. The adults emerge from the soil at night from late spring through autumn and feed on the leaves of a wide range of garden plants, with grapes among their preferred hosts. While adult feeding is unsightly, the larval stage in the soil is far more damaging.

Adult feeding — leaf notches

The adult vine weevil is a dull grey-black beetle about 9 mm long with a characteristic elbowed snout. It cannot fly and feeds only at night, dropping to the soil if disturbed. The U-shaped notches it cuts are immediately diagnostic — no other common pest produces this exact damage pattern on grapevine leaves. Adults are present from late spring to early autumn, and all adults are female (they reproduce parthenogenetically without mating).

Larval damage — the greater threat

Each adult lays hundreds of eggs in the soil in summer. The cream-coloured, C-shaped larvae hatch and feed on fine roots and the surface of larger roots throughout autumn, winter, and spring. Container-grown grapevines are especially vulnerable because larvae are confined to a limited root zone and can sever roots quickly. A pot-grown vine that suddenly wilts and collapses in spring despite regular watering should have its root zone inspected for larvae immediately.

Physical controls for adult weevils

Because adults cannot fly, they must climb the vine's stem to reach the foliage. Wrapping the main trunk with a sticky barrier band traps adults attempting to climb. Placing a sheet under the vine and shaking it on a night-time inspection reveals the adults, which can be collected and destroyed. These methods reduce populations without chemicals.

Biological control with nematodes

The biological control nematode Heterorhabditis bacteriophora (sold as Nemasys Vine Weevil Killer and similar products) is highly effective against larvae in warm, moist soil. Apply in late summer or early autumn when larvae are small and the soil is above 12°C. A second treatment in spring targets any overwintering larvae. This is the most effective and environmentally friendly approach for garden use.

Chemical control

The neonicotinoid imidacloprid (in products such as Provado Vine Weevil Killer) is effective against larvae as a soil drench. However, given concerns about neonicotinoid effects on pollinators, biological control is the preferred approach for most garden growers. Pyrethrin-based sprays applied at night can reduce adult numbers on the foliage.