Flea beetles are an early-season pest commonly found on all members of the cole crop group, as well as spinach, beets, potatoes, and eggplant.  There are several different species of flea beetle that pose problems early in the season when they are considered occasional pests. Host plants of many of the flea beetles are easily identified by their common names. For example, the crucifer flea beetle attacks cole crops and mustards while the eggplant flea beetle is commonly associated with eggplant.

Appearance

Common Wisconsin flea beetles include the cruicfer, eggplant, horseradish, pale-striped, potato, spinach, and striped varieties. All have characteristically large hind legs that give adults the ability to jump. Adult flea beetles range in size from about 1/10 – 1/5 inch. Larvae are delicate and thread-like with white bodies and brown heads.

Symptoms and effects

Adults feed on both leaf surfaces, but usually on the underside where they chew small, circular holes through to the upper cuticle. This cuticle often remains in place for some time before trying and falling out. The circular holes give the plant a “shot-gun” appearance. Heavy feeding on young plants may reduce yields or even kill plants in severe cases. Crops grown for their foliage such as kale, bok choy, spinach, or mustards may be rendered unmarketable by flea beetle damage. Larvae feed on the roots and tubers of susceptible plants but don’t often cause economic damage. Larvae of the horseradish flea beetle also mine the stem and leaf veins. In addition, many are vectors of plant pathogens.

Life cycle

Flea beetles overwinter as adults in the soil or beneath plant debris. They become active in early spring when temperatures reach 50°F, and begin feeding on weeds or early-planted crops. Adults lay eggs in the soil at the base of host plants in May. Eggs hatch in 7-14 days and larvae feed on various plant parts until fully grown. They pupate in earthen cells for 11-13 days before emerging as adults. Adult flea beetles are particularly active on warm, calm, sunny days. Depending upon the species, there may be 1-3 generations per year.

Scouting

Flea beetle populations can be monitored with yellow sticky traps.  The number of beetles found in traps corresponds to the amount of feeding damage occurring nearby.  Scouting for damage should occur every 1-2 days in newly planted fields, because flea beetles can quickly become a problem for young plants.

Management

Cultural control

Adjusting planting dates to avoid damage caused by flea beetles may be useful. Floating row covers can prevent adults from feeding on leaves and laying eggs on the crop. If used, row covers should be set up just before the crop emerges. Water deters adult flea beetles, and any watering should be done in mid-day. Since flea beetles overwinter near fields, planting after adults have emerged or rotating crops can help minimize flea beetle damage. Commercially available nematodes that feed on flea beetle eggs, larvae, and pupae are available.

Chemical control

This option is recommended when flea beetle populations exceed threshold levels, particularly early in the season (see table). Soil-applied insecticides will provide season long control. Foliar insecticides can provide quick control but may also disrupt natural enemies of other pests of cole crops. Reduced risk products such as Proaxis® and Warrior II® should be considered.

Refer to the UW-Extension publication Commercial Vegetable Production in Wisconsin (A3422) for a list of registered insecticides and management recommendations.

Species list

Alticini (Flea beetles)

Disonycha

Disonycha xanthomeles (Spinach flea beetle)

Epitrix

Epitrix cucumeris (Potato flea beetle)

Epitrix fuscula (Eggplant flea beetle)

Phyllotreta

Phyllotreta armoraciae (Horseradish flea beetle)

Phyllotreta cruciferae (Crucifer flea beetle)

Phyllotreta striolata (Striped flea beetle)

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