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Flea Beetles

Garden pest · Alticini

Description​

Flea beetles are a group of small leaf beetles named for their ability to jump when disturbed. Most adults are about 1.5–3 mm long, though size varies by species. They may be black, bronze, metallic, or striped. Adults chew tiny, round holes in leaves, often called “shot holes.” Young plants can lose enough leaf tissue to grow slowly or die, while established plants usually tolerate light damage. Flea beetles attack many garden crops, including brassicas, eggplant, potatoes, and tomatoes; different species favor different hosts. Adults commonly overwinter in sheltered places, become active in spring, and lay eggs near host plants. The larvae of some species feed on roots or underground stems, but adult feeding on leaves is usually the most noticeable problem. Warm, dry weather often favors beetle activity, making newly planted seedlings especially vulnerable when they are least able to withstand damage.

Symptoms​

  • Holes in leaves
  • Stunted growth
  • Wilting

How to Identify​

Look for many small, round holes scattered across leaves, particularly on young plants. Check early in the day or approach slowly: flea beetles often jump away before you can examine them. Their size, jumping behavior, and presence beside fresh shot holes are useful clues. Caterpillars and slugs generally leave larger, less uniform holes; slugs may also leave slime trails. Leaf spots can resemble holes after dead tissue falls out, but spots usually have discolored edges and no jumping beetles nearby. Check which crop is affected, since flea beetle species differ in their preferred hosts. Root-feeding larvae are harder to identify without examining the soil.

Prevention​

Protect susceptible seedlings with fine-mesh insect netting or floating row covers immediately after planting, and seal the edges. Remove covers when plants need insect pollination, or hand-pollinate enclosed crops. Avoid covering a bed where flea beetles may already be overwintering in the soil. Rotate susceptible crops away from heavily infested beds, and remove crop debris and related weeds that can shelter beetles or serve as hosts. Keep seedlings watered and growing steadily; larger, healthy plants withstand feeding better than small, stressed ones. Where practical, start plants indoors and transplant sturdy seedlings rather than sowing directly into an infested bed. Inspect plants frequently in spring so you can protect new growth before damage becomes extensive.

Treatment​

Start by assessing the damage: established plants with a few shot holes often need no treatment. Keep affected plants watered and protect new seedlings with insect netting, provided beetles are not trapped underneath. If practical, use a handheld vacuum to collect adults in the morning, when they are less active. A labeled kaolin-clay product can make foliage less attractive to feeding beetles; coat leaves thoroughly and reapply as its label directs after rain or new growth. Replace badly damaged seedlings if they cannot recover. If beetles continue to threaten young plants, use a pesticide specifically labeled for flea beetles and the crop, following its directions and harvest interval. Spinosad is one option where registered, but it can harm bees while wet. Apply only when needed, avoid spraying flowers or visiting pollinators, and check plants afterward to see whether further action is necessary.

Plants Affected​

Amaranth, Arugula, Bok Choy, Broccoflower, Broccoli, Broccolini, Brussels Sprouts, Cabbage, Cauliflower, Chinese Broccoli, Chinese Cabbage, Collard Greens, Daikon, Eggplant, Horseradish, Kale, Kohlrabi, Komatsuna, Mizuna, Mustard Greens, Napa Cabbage, Okra, Potato, Radish, Rapini, Red Cabbage, Romanesco, Rutabaga, Savoy Cabbage, Sweet Potato, Tatsoi, Turnip, Watercress

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