Sticky leaves and sticky residue

A sticky film on the leaves points to honeydew: the sugary waste that sap-feeding insects excrete as they feed. Aphids, soft scales, mealybugs, whiteflies, psyllids and leafhoppers all produce it. Look above and on the undersides of the leaves, not just at the sticky patch: honeydew coats whatever lies beneath the feeders.

1. Green peach aphidMyzus persicaeMost likelyColonies on the growing points and under young leaves, with white cast skins dropped onto the leaves below. Soft, pear-shaped aphids, pale green, yellowish or pink.Full pest profile →
2. Brown soft scaleCoccus hesperidumMost likelyNothing flies up: flat, oval, pale yellow to brown bumps close to the midrib and main veins on the leaf undersides. Soft scales produce large amounts of honeydew.Full pest profile →
3. Greenhouse whiteflyTrialeurodes vaporariorumAlso commonSmall white adults fly up when you disturb the plant and settle again, wings held flat. The scale-like nymphs under the leaves do not move, and every stage feeds and drips honeydew.Full pest profile →
4. Citrus mealybugPlanococcus citriAlso commonSmall clusters of fluffy white wax in the leaf axils, leaf sheaths and where stems and leaves touch, with the segmented, wax-covered insects underneath. Older ones can still walk.Full pest profile →
5. Potato aphidMacrosiphum euphorbiaeAlso commonMuch bigger and more elongate than the green peach aphid, green or pink, usually on the shoot tips. On tomato it arrives later in the season and produces a large amount of honeydew.Full pest profile →
6. Silverleaf whiteflyBemisia tabaciLess oftenSame picture as the greenhouse whitefly, but smaller and yellower, with the wings held close and tent-like rather than flat. Worth separating: it spreads tomato yellow leaf curl and several bean and cucurbit viruses.Full pest profile →