What's making holes in my vegetable leaves?

Start by matching the holes to a culprit. Dozens of tiny round shot-holes, about the size of a pinprick, on young leaves point to flea beetles. Ragged holes with smooth edges, low on the plant, with silvery slime trails nearby point to slugs. Large holes chewed through the leaf, with green or dark pellet-shaped droppings on the leaves or soil below, point to caterpillars: cabbage worms and loopers on cabbage-family crops, hornworms stripping tomatoes. Lacy leaves with only the veins left point to Japanese beetles or, on beans, Mexican bean beetles. Spots that later turn into holes point to a leaf disease.

Flea beetles are shiny black or bronze beetles about 1/10 inch long that jump like fleas when you brush the plant. Damage is worst on seedlings and new transplants of cabbage-family crops, eggplant, and radishes in spring, and established plants usually outgrow it. Slugs feed at night and on cloudy days and hide by day, so you may not see them unless you look. Go out after dark with a flashlight, or lift a board laid on the soil in the morning. Lettuce, strawberries, and seedlings are frequent targets.

Cabbage worms are velvety pale green caterpillars about an inch long, the young of the small white butterflies seen around brassicas; loopers are similar but arch their backs as they move. Both hide on leaf undersides. Tomato hornworms grow to about 4 inches and can strip whole branches of tomato, pepper, or eggplant, leaving dark pellets on the leaves below. Japanese beetles are metallic green and copper, about 1/2 inch, and feed in groups on the sunny top of the plant. Mexican bean beetles are copper with 16 black spots; they and their spiny yellow larvae feed from the leaf underside, leaving a see-through, lacy leaf.

If you find no insects and the holes started as spots, think disease. Leaf spots with tan or brown centers can dry out and drop away, leaving holes. On peaches, cherries, and plums, this is called shot-hole disease. On cucumbers, melons, and beans, anthracnose and other leaf-spot diseases can do the same in wet weather. These spread on splashing water and wet leaves, so water at the base of the plant, remove badly spotted leaves, and clean up plant debris at the end of the season.

Start with the mildest fix. Hand-pick caterpillars and beetles; knock Japanese beetles into a cup of soapy water in the cool of the morning. For slugs, use board traps, water in the morning instead of the evening, and if needed scatter iron phosphate bait thinly, as the label directs, keeping pets away. Cover young brassicas with row cover at planting to keep out flea beetles and butterflies. For caterpillars on cabbage-family crops, Bt kurstaki works only on young caterpillars that eat sprayed leaves and also harms butterfly caterpillars, so keep it off host plants such as milkweed. Most established plants tolerate some holes.

Before using any product, read the whole label. It must list the crop you’re treating, and its directions on amount, timing, protective gear, bees and days before harvest are legal requirements. If this page and the label disagree, follow the label.