Lettuce Pests. Common bugs on lettuce & leafy greens

Common lettuce pests include lettuce aphid, green peach aphid, potato aphid, western flower thrips, spider mites, whiteflies, leafminers, slugs, snails, cutworms, loopers and other caterpillars. Start with the damage pattern because sticky curled leaves, silver scarring, fine stippling, internal leaf mines and ragged holes point toward different pest groups.

Lettuce aphids can feed deep inside the plant and, in head lettuce, may be concentrated near the heart on younger leaves. Other aphids can begin on lower leaves or young tissue and move through the plant. Open leaf folds and inspect the center rather than checking only the outside of the head.

Western flower thrips can puncture lettuce leaves and leave a silvery surface that later becomes brown scarring. Small black fecal specks in the damaged area support a thrips diagnosis. Wind or abrasive injury can look similar, so inspect folds and leaf undersides for the insects themselves.

Tiny flying insects around lettuce can include adult whiteflies, winged aphids, thrips or fungus gnats around wet container media. Disturb the foliage, then inspect the leaf undersides and growing medium so the flying clue is tied to the right pest.

Leafminer larvae feed between the upper and lower leaf surfaces, creating winding or blotchy mines inside the leaf. Because the insect is protected within the tissue, leafminer damage belongs to a different management path from exposed aphids, thrips, mites or whiteflies.

Ragged holes, missing leaf tissue or clipped seedlings usually point toward chewing pests such as slugs, snails, caterpillars, cutworms or beetles. This damage is different from the stippling, silvering or honeydew associated with small sap-feeding pests.

Start at the outer leaves, turn leaves over, then work inward through folds toward the crown or heart. Look along veins, leaf bases and tightly packed young leaves for aphids, thrips, eggs, cast skins or feeding scars. Inspect several plants because early infestations can be patchy.

Yes. Spider mites can feed on lettuce leaves and may cause fine pale stippling, bronzing or decline. Use a hand lens if needed and inspect the underside of leaves for tiny moving mites, eggs or fine webbing before assuming the damage is from drought or another stress.

Consistent inspection is important because lettuce pests can hide in leaf folds and inside heads. Home gardeners can inspect every plant, while commercial growers need a repeatable pattern across field edges and production blocks. UC IPM recommends regular field monitoring for aphids and thrips, with extra attention to areas where infestations tend to begin.

Lost Coast Plant Therapy controls soft-bodied pests including aphids, thrips, spider mites and whiteflies on contact when used as directed. Cornell evaluated western flower thrips directly on lettuce and reported 95% +/- efficacy in the strongest treatment after five applications. Leafminers inside leaves, slugs, snails, caterpillars and other chewing pests need a different management approach.