Are All Flea Beetles the Same?

E-1274 Are All Phyllotreata cruciferae Flea Beetles Crucifer Flea Beetle Versus the Same? Leafy Spurge Flea Beetles Denise L. Olson Assistant Professor, Entomology Dept. Janet J. Knodel Extension Crop Protection Specialist, NCREC, NDSU Aphthona lacertosa “FLEA BEETLE” is a common name describing many species of beetles that use their enlarged hind legs to jump quickly when disturbed. The adults feed on the leaves of their host plants. Heavily fed-on leaves have a shot-hole appearance. The larvae (wormlike immature stage) usually feed on the roots of the same host plants as adults. Common flea beetles that occur in North Dakota include the Flea beetles crucifer flea beetle (Phyllotreata cruciferae) and the leafy spurge have enlarged flea beetles (Aphthona species). The crucifer flea beetle is a hind legs that non-native insect pest that accidentally was introduced into they use to jump North America during the 1920s. Phyllotreata cruciferae now quickly when can be found across southern Canada and the northern Great disturbed. Plains states of the United States. The leafy spurge flea beetles are non-native biological control agents and were introduced for spurge control beginning in the mid-1980s. These biological control agents have been released in the south-central prov- inces of Canada and in the Upper Great Plains and Midwest Crucifer flea beetle is states of the United States. Although P. cruciferae and Aphthona an exotic insect pest. species are both known as flea beetles and do look similar, they differ in their description, life cycle and preference of host plants. Leafy spurge flea beetle species are introduced biological control North Dakota State University, Fargo, North Dakota 58105 agents. JULY 2005 Crucifer Flea Beetle Description The crucifer flea beetle is known to The adult is a small (about 1/32 to 1/8 be attracted to mustard oils. Mustard inch), oval-shaped, bluish-black beetle oils are common components among with numerous dimples on the wing the plants selected by the crucifer covers (Figure 1). The whitish larva is beetle, suggesting that these com- wormlike and approximatley 1/8-inch in pounds are the basis for host plant size, with tiny legs and a brown head. selection by this flea beetle species. Life Cycle Feeding Injury The crucifer flea beetle has one The overwintered adults cause the generation per year. Adult flea beetles injury to their host plants. In the spring, overwinter in leaf litter of shelterbelts they feed on the seedlings, producing and grassy areas. They emerge from pits in the tissue of the cotyledons and the overwintering sites during early first true leaves. As the leaf tissue spring as temperatures reach up to dies around the pits, the cotyledons 57 F. and leaves appear shot-holed (Figure Figure 1. Crucifer flea beetle Volunteer canola and wild mustard 2). Plant stand and plant growth can are usually the first available host be reduced and maturity delayed when plants, with the beetles moving into the crucifer flea beetle feeds on the the new canola fields as the crop seedling stage of its host plants. The emerges. Overwintered adults are larvae feed on secondary roots of host usually active in the fields until late plants but this feeding has a negligible June, feeding on the foliage and effect on plant vigor or yield. After depositing their eggs in the soil. The “mid-July, summer adults feed on the larvae can be found in the root zone developing pods or seeds (Figure 3). Overwintered adults of host plants during June and July. The host plant can have poor seed feed on seedling The pupal stage occurs from early fill, premature pod drying, shriveled cruciferous host to mid-July. The new generation, or seed, or pod shattering from these plants. Summer summer adults, are present from late infestations. July to early September. They can be adults feed on the found feeding on the pods of canola, pods of canola, mustard, and cruciferous weeds. mustard and The summer generation will move cruciferous weeds. to overwintering sites in early fall. Host Plants The crucifer flea beetle is an economic pest of oilseed Brassica (canola) and has a narrow host range restricted to plants in these families: Capparidaceae – clammyweed and spider plant; Tropaeolaceae – nastur- tium; Limnanthaceae – meadow-foam; Cruciferae – candytuft, cow-cress, poor-mans pepper, shepherds-purse, radish, charlock, turnip, cabbage, cauliflower, broccoli, hedge-mustard, common wintercress and honesty. Figure 2. Crucifer flea beetle feeding injury Figure 3. Adult crucifer flea beetles feeding on mature stems and pods of canola. Leafy Spurge Flea Beetle Six Aphthona flea beetle species were conditions. The newly emerged larvae released in North Dakota for biological tunnel into the soil searching for the control of leafy spurge. Of these leafy spurge fibrous roots (feeder six species, the black flea beetle, roots) near the soil surface. Second A. lacertosa (Figure 4), and the brown and third instar larvae (Figure 6) feed flea beetle, A. nigriscutis (Figure 5), on the larger roots and root buds. are the two species that have been the The third instar larvae move deeper most successful and most commonly into the soil to overwinter as the soil are redistributed to areas infested with temperature falls below 45 F. leafy spurge. The first release of A. lacertosa in North Dakota was in 1988 Host Plants and A. nigriscutis first was released in Both leafy spurge flea beetles feed 1989. These two species have reduced exclusively on plants in the family leafy spurge to a nonweed problem in Euphorbiaceae (spurges). Variation some areas of North Dakota. in plant structure and habitat of the spurge species recorded as hosts Description suggest that secondary compounds, Figure 4. A. lacertosa Aphthona flea beetles appear shiny or possibly latex, are important in this “polished” rather than being “dimpled” strong relationship between spurges as in the economically important and their flea beetles. Before releasing crucifer flea beetle, and they are the Aphthona flea beetles into the approximately 0.10 inches long. The United States, host specificity tests brown flea beetle, A. nigriscutis, has were conducted using several eco- a clearly visible dark brown to black nomic plants including canola, beet, triangular mark directly below the corn, potato, sweet potato, carrot, thorax and between each wing cover rhubarb, and a perennial herb. None (Figure 5). The black flea beetle, of these crops serve as hosts for the Aphthona lacertosa, is actually Aphthona species released into the metallic blue and the enlarged United States. segment of the hindlegs is yellow to brown (Figures 4 and 6). Feeding Injury The adult spurge flea beetles feed on Life Cycle the foliage of leafy spurge (Figure 8). The leafy spurge flea beetles have However, it is the feeding by the larvae one generation per year. However, they on the root system that causes the overwinter as third instar larvae (Figure greatest damage to spurge and results 7) in the soil near the spurge roots. The in stand reduction. First instar larvae larvae resume feeding on the spurge feed on the fine feeder roots, which roots as the soil temperature exceeds reduces water and nutrient uptake. Figure 5. A. nigriscutis 45 F in April and May. Root feeding Second and third instar larvae reduce continues into late May and early the energy storage tissue of the root June, at which time they enter the crown by feeding on the larger roots. pupal stage. The adults emerge from In addition, the plant becomes more the soil during late spring into early susceptible to herbicides and infection Aphthona lacertosa and summer and feed on the spurge from soil-borne pathogens after the A. nigristus have been the vegetation and lay eggs in the cracks larvae have injured the root system. of the soil near the base of the leafy most successful against spurge stems. Aphthona lacertosa and leafy spurge. A. nigriscutis adults live for about 1½ months in hot and dry conditions, and up to two months in cooler, wetter The leafy spurge flea beetle larvae overwinter in the soil near the spurge roots. Crucifer Leafy Spurge Flea Beetle Flea Beetle Common & Crucifer flea beetle Leafy spurge flea beetles Scientific (Phyllotreta cruciferae) (Aphthona spp.) Name Figure 6. A. lacertosa Host Crucifeae – Leafy spurge Plants Genus Brassica Mustard, Canola Host Plant Mustard oils Possibly secondary plant Attraction compounds (latex) Life Cycle One generation per year. One generation per year. Adults overwinter Third instar larvae in grassy areas in overwinter near the roots shelterbelts, ditches of spurge. and field margins. Figure 7. Aphthona flea Damaging Overwintering adults on Larvae on the roots beetle larva Stage young seedlings Photograph credits: Figure 1, 4, 5, 6 – Gerald Fauske, Department of Entomology, NDSU Figure 2, 3 - Janet Knodel Figure 7 - Denise Olson Figure 8, Cover (Aphthona lacertosa) – USDA-APHIS-PPQ Cover (Phyllotreata cruciferae) – Lloyd Harris, Regina, SK, Canada Figure 8. Adult Aphthona on spurge foilage For more information on this and other topics, see: www.ag.ndsu.edu NDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and U.S. Department of Agriculture cooperating. Duane Hauck, Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. We offer our programs and facilities to all persons regardless of race, color, national origin, religion, sex, disability, age, Vietnam era veterans status, or sexual orientation; and are an equal opportunity employer. This publication will be made available in alternative format upon request to people with disabilities (701) 231-7881. 5M-7-05.

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