Why Are My Grapevine Shoots Sticky with Aphids?

Sticky grapevine shoot tips colonised by small soft-bodied insects, with curled or distorted leaves at the growing points, are being attacked by aphids. Several aphid species affect grapevines, feeding on the sap of young growth and excreting honeydew — the sticky residue that coats leaves and can lead to sooty mould development. Aphid populations can build up quickly in spring and early summer before natural predators arrive in sufficient numbers to bring them under control.

Species commonly found on grapevines

The grape aphid (Aphis illinoisensis) and various generalist green or blackfly species can colonise grapevines. Unlike the root-feeding grape phylloxera (which is a separate pest entirely), these are soft-bodied insects feeding on the above-ground sap of young shoots and leaf undersides. Colonies are often attended by ants, which protect them from natural predators in exchange for honeydew — disrupting the ant-aphid relationship helps populations decline faster.

Assessing the level of damage

Light aphid infestations on a vigorous vine cause minimal real harm. The distorted shoot tips at the tip of affected shoots are an inconvenience, but the vine grows past them quickly. Heavy infestations on young vines, on container-grown plants, or concentrated on flower trusses close to fruit set can reduce fruit set and vigour more significantly. The honeydew also creates a substrate for sooty mould, which reduces the photosynthetic capacity of affected leaves.

Physical removal

Rubbing aphid colonies off shoot tips with your fingers, or blasting them with a strong jet of water, removes them without chemical intervention. This is most effective when done promptly before the colony becomes very large. Pinching out the tip of heavily infested shoots (once the shoot has reached the required length) removes the colony and the soft new growth that attracts aphids.

Soft soap or insecticidal soap sprays

A spray of diluted liquid soap (not detergent) or a purpose-made insecticidal soap product coats and suffocates aphids on contact. It has very low residual activity and needs to hit the insects directly, so thorough spray coverage of the undersides of leaves is essential. It does not harm aphid predators that arrive after the spray has dried, making it compatible with biological control in greenhouse situations.

Encouraging natural predators

A garden rich in flowering plants attracts hoverflies (whose larvae consume thousands of aphids), ladybirds, lacewings, and parasitic wasps. These natural enemies typically arrive a few weeks after an aphid colony establishes and can collapse large populations rapidly without any intervention. Avoiding broad-spectrum insecticides — especially in spring — preserves this free pest control service.