Flea Beetle

Host Plants

Flea beetles attack a wide range of flora, including garden plants such as radishes, broccoli, cabbage, turnips, eggplant, peppers, tomatoes, potatoes, spinach, and melons.

Regions impacted

Europe, North America, and many other temperate climates.

Description

• There are many species: some attack a wide range of plants, while others target only certain plant families. Most adults are very small (1/16 –1/8 inch long).
• Given that there are so many species, they vary in appearance. They can be black, bronze, bluish, or brown to metallic gray. Some may have a solid, striped, or spotted pattern.
• All flea beetles have large back legs, which they use very effectively for jumping, especially when disturbed. Given their tiny size and penchant for springing away when approached, they can be hard to detect.
• Larvae at about ¾ inch in length are thin, white, and legless and sport brown heads.

Life Cycle

• Flea beetles overwinter as adults in leaf litter and wooded areas and emerge from the soil in spring to feed and mate.
• Depending on the species, females lay single or clusters of eggs in holes, in roots, soil, or on leaves and flowers of many vegetables.
• Eggs hatch in about a week, and the larvae feed on the roots of their host for 2 to 3 weeks, then pupate in the ground – adults emerge 2 to 3 weeks later.
• There are usually one to two generations per year.

Damage and Detection

• Adult flea beetles cause the most damage by feeding on the leaves and stems of most vegetable crops and flowers. They create small, rounded, irregular holes (usually less than 1/8 inch) in the leaves as they feed.
• They are most damaging in early spring when plants are less established. Flea beetle injury is most acute when seedlings are becoming established or during the production of leafy vegetables. Growth may be seriously stunted, and in more severe infestations, plants can be killed.
• Injuries are usually minor and are readily outgrown on established plants – on established plants, 20-30 percent or more of the leaf area must be destroyed before there is any effect on yield.
• Larvae of most flea beetles feed on the roots and cause little to no damage to the plants (except potato flea beetle larvae)
• Flea beetles are big jumpers and tiny, so detection is not easy.

Prevention and Control

Monitor your garden

• Flea beetles are most damaging in spring; monitor activity as soon as seedlings have emerged.
• Use white sticky traps to capture these pests.
• Dust leaves with plain talcum powder to repel flea beetles on tomatoes, potatoes, peppers, and other plants.
• Apply garlic spray or kaolin clay to plants to repel the beetles
• Collect beetles off foliage using sweep nets or a portable vacuum. The beetles are jumpers, so this can be time-consuming and must be repeated frequently as the reinvasion of plants can be rapid.
• Flea beetles are most problematic during droughts; watering the garden can sometimes reduce outbreaks.

Cultural controls

• Because seedlings are most at risk, use transplants or plant seeds in a well-prepared seedbed to hasten growth.
• Delay planting to avoid peak beetle population. Plants grow faster in warmer temperatures and, when established, are better able to resist flea beetle damage.
• Use row covers or other screening to keep beetles out when seedlings are establishing themselves; remove before flowers appear to allow pollinating insects access.
• Control weeds in and around planting sites to limit food sources for flea beetles. Remove old crop debris to minimize cozy overwinter shelters.
• Flea beetles can be kept away from crops by planting strongly-scented plants such as catnip, sage, mint, or hyssop nearby.
• Plant trap crops such as radish or basil before the main crop is planted to attract flea beetles away from the main crop. The trap crop may then be harvested or destroyed after the main crop has established itself sufficiently.
• These beetles prefer full sun, so interplant crops to provide shade for susceptible plants.

Biological controls

• Several natural predators can be employed to keep flea beetles in check, including braconid wasps and tachinid flies. In both cases, these attack the larvae, not the adult beetles.
• To encourage these natural predators/helpers, flowers such as caraway, herb fennel, and coriander can be planted between crops.
• California poppies, pot marigolds, and yarrows will also attract these natural predators.

Pesticides

• There are many insecticides labeled for treating flea beetles.
• Use chemical insecticides as a last resort, given the impact on natural predators and other wildlife.