Why Are There Holes in My Lettuce Leaves?

Holes in lettuce leaves mean something is eating your crop, and since you eat those leaves yourself, it is worth identifying the culprit and acting fast. Lettuce is soft, tender and low to the ground, which makes it a favourite of several common garden pests. The size and shape of the holes, and the time of day the damage appears, point to which one. Let me show you how to read it.

Slugs and snails: the prime suspects

By far the most common cause of holes in lettuce is slugs and snails. Lettuce is one of their favourite foods, and they leave large, ragged holes, often eating from the leaf edges inward, and shredding young plants entirely. The giveaway is silvery slime trails on the leaves, soil or pots in the morning. They feed at night and in damp weather and shelter in cool, moist spots by day. Hunt them after dark with a torch and hand-pick, set beer traps, clear damp hiding places near the plants, and ring the bed with a gritty barrier they dislike crossing. Slugs love the moist, sheltered conditions lettuce also enjoys, so they are a constant battle.

Caterpillars

Various caterpillars, including cutworms, loopers and cabbage-family caterpillars, chew holes in lettuce leaves, often larger and more irregular than flea-beetle damage, sometimes with dark droppings nearby. Loopers and similar can hide in the heart of the plant. Hand-pick the caterpillars you find, and use Bt, a natural caterpillar control harmless to other creatures, for heavier infestations. Inspect the inner leaves and undersides, where they often hide during the day.

Earwigs and beetles

Earwigs feed at night and chew small, ragged holes in lettuce leaves; they hide in dark crevices by day, and a rolled-up damp newspaper left out overnight traps them for removal. Flea beetles can pepper lettuce seedlings with tiny round shotholes, especially in warm weather, and are most damaging to young plants. Other beetles may chew larger holes. If the damage is many tiny holes on seedlings with beetles jumping away, that is flea beetles; small ragged holes appearing overnight with no slime suggests earwigs.

Match the damage and protect the crop

Put it together: large ragged holes with silvery slime trails equals slugs and snails — hunt at night and set barriers; larger holes with droppings, pests in the heart, equals caterpillars — hand-pick or use Bt; tiny shotholes on seedlings with jumping beetles equals flea beetles — protect young plants; small ragged holes overnight with no slime equals earwigs — trap them. The best all-round protection for lettuce is floating row cover, which excludes most of these pests while letting in light and water, plus diligent slug control. Wash harvested leaves well, especially from a slug-prone bed, since pests can hide in the heart.