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Origin and Distribution
The bagrada or painted bug, Bagrada hilaris (Burmeister), is a recently introduced pest of cruciferous crops and weeds in the western United States. Native to Africa, it also is known from India, Pakistan, Sri Lanka, the Middle East and Italy. Introduced in 2008, it is presumed to have entered via the Port of Long Beach in container cargo. It has spread eastward into Arizona, Nevada, and New Mexico.
The bagrada bug is a plant-feeding stink bug, primarily attacking plants in the mustard family Brassicaceae. It feeds on weeds, flowering plants, and cultivated mustards such as arugula, Asian greens, India mustards, broccoli, brussels sprouts, cabbage, cauliflower, canola, radish, and turnip. In addition it feeds on grasses such as corn, Sudan grass and Bermuda grass. In other countries it is reported on capers, potatoes, cotton, and legumes.
Potential Impact and Spread
The distribution of brassicaceous weeds is thought to have contributed to the range expansion of bagrada bug. In the southwestern U.S., mustard weeds grow in the winter, providing bugs with ample food at times when crops approach harvest and become tough and less desirable. As temperatures increase, bug density can rapidly increase. Weeds along highways and irrigation canals provide corridors into agricultural areas. The late summer planting of commercial mustard and cole crops serve as hosts for bugs that survive the summer. Since these crops are just sprouting at the end of summer, feeding by the insects quickly destroys the plants.
Life Cycle and Identification
Adult males and females are similar in appearance, measuring 5–7 mm, with the female being larger. The dorsum of both sexes is black with orange and white spots, and the underside of the abdomen can vary from black to dark cream. Although known in the Old World as the harlequin bug, it is much smaller and has distinctly different markings from our New World harlequin bug, Murgantia histrionica (Hahn). Adults are commonly found copulating and positioned end-to-end. The bagrada bug overwinters in the adult stage and lays eggs in the spring through early fall. The eggs, unlike other stink bugs, are laid individually or in small groups (<10). Eggs are laid on the undersides of leaves, hairy stems of plants, and in cracks in the soil. New eggs are slightly barrel shaped and dirty white, gradually becoming orangered as the embryo develops. Upon hatching, nymphs are reddish. The legs, head and thorax gradually darken within hours of hatching and the nymphs resemble small adult lady beetles. There are 5 nymphal stages. Later instars exhibit elaborate markings, and the 5th instar shows white markings on the thorax and abdomen along with the presence of wingpads. Aggregations containing both nymphs and adults become increasingly common as densities increase, generations overlap, and food sources decrease. Multiple generations per year exist in the warm desert areas. The generation time is 2–3 weeks during the summer months. While these bugs will lay eggs at cool temperatures, it must be warmer than 75°F for newly eclosed nymphs to feed.
Damage (Plant Symptoms)
The bagrada bug inserts its needle-like mouthparts into plant tissues, injects digestive enzymes and sucks the juices. With lacerate-and-flush feeding, the mouthparts are inserted, retracted and inserted again at a different angle. This results in a starburst-shaped lesion. These bugs feed primarily on leaves, flowers and young seed pods. Feeding on apical meristems of young seedlings may either kill the plant, result in plants that do not produce a flower, or induce adventitious branching of the stem. In headforming crops, this results in no heads being formed or multiple small heads. Foliage feeding results in wilting, scorching and curling of the leaf and ultimate death of the leaf tissue.
Chemical control includes chemigation and contact insecticides once direct-seeded plants emerge. For transplants and established fields additional chemical options are available and may be considered. Monitoring for insects in the morning after temperatures are above 85°F is important as populations may be highly localized. Leaves with star-shaped lesions may be easier to spot than the insects themselves. In young cole crop fields, bugs may be found at the plant/soil interface during early morning and late afternoon when temperatures are cooler.
For information about the Pest Alert program, please contact Laura Iles, co-director of the North Central IPM Center, at email@example.com.
This publication was produced and distributed by USDA-NIFA Regional IPM Centers and the 1862 Land-Grant Universities.
Thomas M. Perring and Darcy A. Reed, Department of Entomology, University of California, Riverside, CA 92521
John C. Palumbo, Department of Entomology–Yuma Agricultural Center, University of Arizona, Yuma, AZ 85364
Tessa Grasswitz, Department of Entomology, Plant Pathology and Weed Science, Extension Plant Sciences, New Mexico State University, Los Lunas, NM 87031
C. Scott Bundy, Department of Entomology, Plant Pathology and Weed Science, New Mexico State University, Las Cruces, NM 88003
Walker Jones USDA-ARS, Biological Control Unit, Stoneville, MS 38776
Monica Papes, Department of Zoology, Oklahoma State University, Stillwater, OK 74078
Tom Royer, Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078
This work is supported by the Crop Protection and Pest Management Program (2014-70006-22486) from the USDA National Institute of Food and Agriculture.