A3720-E Flea GUniversityARDEN of Wisconsin–ExtensionFACTS Flea Beetles K.A. Delahaut

Flea beetles are an early season Appearance commonly found on all Common Wisconsin flea beetles members of the cole crop group, include the crucifer, eggplant, as well as spinach, beets, pota- horseradish, pale-striped, potato, toes and eggplant. There are sev- spinach and striped varieties. All eral different species of flea bee- have characteristically large hind tle that pose problems early in legs that give adults the ability to the season when they are consid- jump. Adult flea beetles range in ered occasional pests. Host 1 1 size from about ⁄10– ⁄5 inch. plants of many of the flea beetles Larvae are delicate and thread- are easily identified by their com- like with white bodies and brown mon names. For example, the cru- heads. Flea damage on Swiss chard. cifer attacks cole crops and mustards while the eggplant Symptoms and effects flea beetle is commonly associated with eggplant. Adults feed on both leaf surfaces, but usually on the underside where they chew small, circular holes through to the upper cuti- cle. This cuticle often remains in

Common Wisconsin flea beetles Common name Scientific name Description Host plants Crucifer flea beetle cruciferae greenish or bluish-black; and other 1⁄16- to 1⁄8-inch crucifers including horseradish 1 Eggplant flea beetle Epitris fuscula black; ⁄16-inch eggplant Horseradish flea beetle Phyllotreta armoraciae black with yellow stripes; horseradish and other 1⁄8-inch mustards Pale- blanda dark brown with 2 broad bean, beet, eggplant, white stripes down its back; lettuce, melon, pea, 1 ⁄6-inch pepper, pumpkin, radish 1 Potato flea beetle Epitrix cucumeris dull black; ⁄16-inch potatoes, tomato, eggplant, pepper Spinach flea beetle Disonycha xanthomeles greenish-black with a yellow spinach and beets 1 thorax; ⁄5-inch Striped flea beetle Phyllotreta striolata black with 2 crooked yellow cabbage strips running down its back; 1⁄12-inch ARDEN ACTS University of Wisconsin–ExtensionG F place for some Flea beetle life cycle time before drying Egg Pupa Adult and falling out. The circular holes give the plant a “shot- gun” appearance. When to scout for flea beetle Heavy feeding on April May June July August September young plants may early mid late early mid late early mid late early mid late early mid late early mid late reduce yields or even kill plants in severe cases. Control quickly, newly planted fields Crops grown for their foliage should be scouted for or such as , bok choy, spinach Cultural: Adjusting planting dates damage every 1–2 days while or mustards may be rendered to avoid damage caused by flea plants are small and unable to unmarketable by flea beetle dam- beetles may be useful in some sit- withstand much damage. Soil- age. Larvae feed on the roots uations. Enclosing seed beds with applied insecticides at planting and tubers of susceptible plants floating row covers protects plants will provide season-long control. but don’t often cause economic from egg-laying adults. Removing Foliar insecticides provide quick damage. Larvae of the horserad- alternate weed hosts, deep plow- control of large populations of ish flea beetle also mine the stem ing of crop residues in the spring adult flea beetles. When select- and leaf veins. In addition, many and crop rotation will help reduce ing foliar insecticides, choose are vectors of plant pathogens. populations. chemicals that will not disrupt the Life cycle Chemical: Chemical control is natural enemies of other pests recommended when flea beetle such as lepidoptera on cole Flea beetles overwinter as adults populations exceed threshold crops. Insecticides with a short in the soil or beneath plant levels, particularly early in the residual life are recommended. debris. They become active in season. Commercial fields should Refer to the UW-Extension publi- early spring when temperatures be scouted for adults with an cation Commercial Vegetable reach 50°F, and begin feeding on sweep net. Because flea Production in Wisconsin (A3422) weeds or early-planted crops. beetles can move into a field for a list of registered insecticides. Adults lay eggs in the soil at the base of host plants in May. Eggs Established control thresholds for various crops hatch in 7–14 days and larvae feed on various plant parts until Crop Threshold fully grown. They pupate in earth- Beets Treat when beetles cause stand reduction on small plants en cells for 11–13 days before Cole crops Undetermined emerging as adults. Adult flea Eggplant <3 inches = 2 beetles/plant beetles are particularly active on warm, calm, sunny days. 3–6 inches = 4 beetles/plant Depending upon the species, >6 inches = 8 beetles/plant there may be 1–3 generations Horseradish Treat only if beetles are found in high numbers early in the per year. season Potato >2 beetles/sweep Tomato >2 beetles/plant

Author: K.A. Delahaut is an outreach specialist with the Integrated Pest Management Program of the University of Wisconsin–Madison and the University of Wisconsin–Extension, Cooperative Extension. Thanks to Jeff Wyman and Phil Pellitteri for reviewing this information. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, University of Wisconsin–Extension, Cooperative Extension. University of Wisconsin–Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. If you need this information in an alternative format, contact the Office of Equal Opportunity and Diversity Programs or call Extension Publishing at (608) 262-2655. © 2001 by the Board of Regents of the University of Wisconsin System. Send inquiries about copyright permission to: Director, Cooperative Extension Publishing, 201 Hiram Smith Hall, 1545 Observatory Dr., Madison, WI 53706. To see more Cooperative Extension publications, visit our web site: www.uwex.edu/ces/pubs/ Flea Beetles (A3720-E) I-2/2001