Flea Beetles Fact Sheet No

Flea Beetles Fact Sheet No. 5.592 Insect Series|Home and Garden by W.S. Cranshaw* Flea beetles are small beetles that jump. if any, significant damage to the plants. Quick Facts The adult beetles feed on leaves, chewing Exceptions include larvae of the tuber flea small pits that produce shothole wounds, beetle, which can cause scarring of potato • Flea beetles are small beetles resembling injuries that might be produced tubers, and larvae of flea beetles that feed that jump when disturbed. by fine buckshot. Young stages (larvae) of on leafy spurge. Flea beetles that develop • They damage plants by most flea beetles feed on the roots but some in the soil as larvae often can produce 2 or develop chewing leaves. 3 generations a season, such as the “cabbage chewing small “shotholes” in Young plants and seedlings are flea beetles” and the “potato flea beetles”. the foliage. particularly susceptible to flea beetle damage. A small number of flea beetles have larvae • Flea beetles can be found Growth may be seriously retarded and in that develop on the leaves of plants. Apple on a wide variety of plants. severe infestations plants can be killed. The flea beetle, which has larvae that develop However, most flea beetles holes in leaves also damage plant appearance, on evening primrose, is an example of a attack only a few, closely which can be important when growing flea beetle with this habit. The types of flea certain leafy vegetables and ornamental beetles have larvae that are black or gray and related plant species. flowers. have small legs. The larvae produce large • Flea beetle injury is most Dozens of species of flea beetles are found and irregular holes in leaves rather than important when seedlings in Colorado (Table 1). Although there is shotholes. Flea beetles that develop on leaves are becoming established some overlap of tastes, each type of flea beetle include the larger kinds of flea beetles, with or in the production of leafy has a decided preference for certain plants. apple flea beetle being the most common vegetables. Injuries are For example, some flea beetles feed only on species. Adults do not make shotholes but potatoes, tomatoes and other members of chew in a more generalized pattern. Flea usually minor and easily the nightshade family. Others have a taste for beetles with larvae that develop on leaves outgrown on established broccoli, cabbage and other crucifer crops. often have only a single generation a year but plants. One group of flea beetles (Aphthona species) the adults may be present for several months. was purposefully introduced into the state to feed on and help manage leafy spurge, an important invasive weed. Flea Beetle Management Although flea beetles are common, injuries often are insignificant to plant Life History and Habits health. On established plants, 20-30 percent Flea beetles spend the winter in the adult or more of the leaf area must be destroyed stage, hidden under leaves, dirt clods or in before there is any effect on yield. The plants other protected sites. They typically begin to most likely to benefit from treatment are become active during warm days in early- more sensitive seedlings, plants grown for mid Spring and then seek out the types of plants on which they feed. Flea beetles can fly well and may fly long distances in search of suitable plants. Adults of all flea beetles feed on leaves of plants. However, immature stages (larvae) may have differing habits. Most develop in the soil, feeding on plant roots. Soil-dwelling © Colorado State University flea beetle larvae are very small, pale-colored Extension. 2/99. Revised 1/19. and worm-like. Normally they cause little, extension.colostate.edu Figure 1: Adult flea beetles chew small pits in the leaf surface. This produces a type of injury known * W.S. Cranshaw, Colorado State University Extension as a shothole. entomologist and professor. 1/19. ornamental purposes or for edible greens, and disease producing pathogens. and potatoes that may be affected by tuber Most of these attack larval stages and flea beetle larvae. these regularly help reduce overall populations of flea beetles. However, flea Cultural Controls beetle adults are highly mobile and no Because seedlings are most at risk, biological controls that can be applied by use transplants or plant seeds in a well- a gardener will likely reduce flea beetle prepared seedbed to hasten growth and damage in a planting. allow plants to overcome injury. In home gardens, try high seeding rates to spread Chemical Controls the injuries produced by adult feeding. Thin When high numbers of flea beetles the plants once they are established and less Figure 2: Seedling plants are most susceptible are present on plants and threaten injury susceptible to damage.Trap crops work in to serious flea beetle damage. insecticides are usually the most effective some situations. This involves purposefully means to manage the problem (Table 2). planting a highly favored crop to attract flea Some flea beetle products act to repel flea beetles away from the main crop. The best beetle feeding (e.g. diatomaceous earth, regional example of this practice involves kaolin clay) but most can kill flea beetles. use of radish or daikon to protect seedlings However, among those insecticides there of other crucifers (e.g., broccoli, cabbage, is a considerable range in how long they Brussels sprouts) that are susceptible to can work to protect plants from flea western black flea beetle and crucifer flea beetles – from a few hours (pyrethrins) beetle. The trap crop may then be harvested to several days (cypermethrin, or destroyed after the main crop has cyhalothrin). Since the most serious established itself sufficiently to outgrow flea problems with flea beetles involve beetle injury. species that are highly mobile and readily It may also be possible to avoid injury Figure 3: A leafy spurge flea beetle. Three reinvade plantings (cabbage flea beetles, by scheduling plantings so that seedlings species of flea beetles occur in Colorado that apple flea beetle), insecticides with are emerging during periods of low flea feed on leafy spurge, a serious invasive weed. longer persistence will usually work best. beetle activity. Cabbage flea beetles are Often more than one application may be usually most damaging in June, when they needed to protect seedling crops since move from winter annual mustard weeds, leaf growth produced after application such as flixweed, on which the early spring will be little protected. are properly generation develops. Most vegetable crops registered for use on the crop. that are well established can tolerate a large As with all pesticides, carefully amount of injury by flea beetles without read and follow all label directions. Pay affecting yield. particular attention to ensure that any flea beetle insecticides being considered Mechanical and Physical Controls are properly registered for use on the Floating row covers or other screening crop. can exclude the beetles during seedling Figure 4: Larva of a western black flea beetle. establishment. In isolated plantings, thick Most flea beetle larvae develop on the roots of mulches may also help reduce the number plants. of flea beetles by interfering with activity of the root and soil stages. mulches may also help reduce the number of flea beetles by interfering with activity of the root and soil stages. Flea beetles can be collected off foliage using sweep nets or a portable vacuum. Care must be made when using these methods as flea beetles will readily jump from plants and escape treatment. Sweep Figure 6: Apple flea beetle larvae develop net/vacuum treatments must be repeated on the leaves and flowers of evening frequently as reinvasion of plants can be primrose. rapid. Figure 5: Surface wounding of potato caused by feeding injuries of the tuber flea beetle. Biological Controls There are numerous natural enemies of flea beetles – predators, parasitoids, Figure 9: Leafy vegetables, particularly Figure 7: Adult apple flea beetles feed on leaves brassicas such as arugala, mustard greens, and of many garden flowers, shrubs and vines. Chinese cabbage are among the plants that are Figure 11: “Spinach flea beetles” are most damaged by flea beetles. common on pigweeds and related weeds and only rarely damage garden vegetables. Figure 8: Flea beetle feeding normally causes Figure 10: Palestriped flea beetle has a wide little effect to well established plants. These host range and can be found on many vegetable injuries were produced by potato flea beetle, the and flower crops. common flea beetle on potatoes and tomatoes. Table 1: Some common flea beetles found in Colorado. Common name (s) Scientific name(s) Host plants, comments Cabbage flea beetles Phyllotreta pusilla, P. Wide host range, primarily of cabbage family plants (Cruciferae family). Western black flea (western black flea beetle, cruciferae beetle is the most damaging flea beetle species in the state. Two and occasionally three crucifer flea beetle) generations are typical. Winter annual mustards, such as flixweed, are important early season hosts for these insects. Palestriped flea beetle Systena blanda Has the widest host range of all flea beetles including squash, beans, corn, sunflowers, lettuce, potatoes and many weeds. Potato flea beetles Epitrix cucumeris, E. Tomato, potato and other nightshade family plants. Occasionally they may chew on and scar subcrinita, E. parvula developing fruit. Tobacco flea beetle Epitrix hirtipennis Eggplant and some other nightshade family plants. Most common in warmer areas of the state. Tuber flea beetle Epitrix tuberis Potatoes. Larvae are associated with tuber injuries. Horseradish flea beetles Phyllotreta armoraciae, Horseradish, occasionally other mustards. P. albionica Leafy spurge flea beetles Aphthona flava, A. lacer- These three flea beetles were purposefully introduced into Colorado to help control leafy tosa, A.

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