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.
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.
Table 1. Common Wisconsin flea beatles
|Common name||Scientific name||Description||Host plants|
|Crucifer flea beetle||Phyllotreta cruciferae||greenish or bluish-black; 1/16″ to 1/8″||cabbage and other crucifers including horseradish|
|Eggplant flea beetle||Epitrix fuscula||black; 1/16″||eggplant|
|Horseradish flea beetle||Phyllotreta armoraciae||black with yellow stripes; 1/8″||horseradish and other mustards|
|Pale-striped flea beetle||Systena blanda||dark brown with 2 broad white stripes down its back; 1/6″||potatoes, tomato, eggplant, pepper|
|Potato flea beetle||Epitrix cucumeris||dull black; 1/16″||potatoes, tomato, eggplant, pepper|
|Spinach flea beetle||Disonycha xanthomeles||greenish-black with a yellow thorax; 1/5″||spinach and beets|
|Striped flea beetle||Phyllotreta striolata||black with 2 crooked yellow strips running down its back; 1/12″||cabbage|
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.
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.
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.
Table 2. Established control thresholds for various crops
|Beets||Treat when beetles cause stand reduction on small plants|
|Eggplant||<3″ = 2 beetles/plant
3-6″ = 4 beetles/plant
>6″ = 8 beetles/plant
|Horseradish||Treat only if beetles are found in high numbers early in the season|
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.
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.
UW-Extension fact sheets
- Flea Beetles (HXT1106-2005)
- Flea beetles (A3720-2001)
- Degree days for fruit and vegetable pests (XHT1087-2005)
- Insect Pest Management for Greenhouses (A3744)
- Commercial Vegetable Production in Wisconsin (A3422)
- Biological Control of Insects and Mites (A3842)
- Biological Control of Greenhouse Pests (NCR58)
- Managing Insects in the Home Vegetable Garden (A2088)
- Flea beetles: Organic control options – ATTRA publication
Alticini (Flea beetles)
Disonycha xanthomeles (Spinach flea beetle)
Epitrix cucumeris (Potato flea beetle)
Epitrix fuscula (Eggplant flea beetle)
Phyllotreta armoraciae (Horseradish flea beetle)
Phyllotreta cruciferae (Crucifer flea beetle)
Phyllotreta striolata (Striped flea beetle)