How to Manage Pests
Pests in Gardens and Landscapes
The Bagrada bug, Bagrada hilaris, also called the painted bug, is a stink bug that attacks various vegetable crops, weedy mustards and several ornamental plants within the mustard family (Brassicaceae) such as sweet alyssum, stock, and candytuft. It is particularly devastating to young seedlings and leafy mustard greens.
Bagrada bugs often infest wild mustard weeds, which are pervasive in California on hillsides and in agricultural corridors in late winter to early spring. Populations rapidly increase in the weeds when seasonal temperatures rise. Record numbers of bugs can invade newly planted cole crops after mustard weeds dry out in late summer.
The Bagrada bug is an invasive pest species, native to Africa, which has spread to India, Pakistan, parts of Southeast Asia, and Italy. In the United States, it was first found in Los Angeles County in 2008. By 2011, the pest had disseminated throughout Southern California to include San Diego, Imperial, Orange, Riverside, San Bernardino, and Ventura counties. In September 2012, the pest moved northward to Santa Barbara and San Luis Obispo counties and recently (2013) the Bagrada bug was found in Fresno, Tulare, and Monterey counties. Other states where this stink bug is currently found include: Arizona, New Mexico, Nevada, Utah, and Texas.
Adult bugs are black with orange and white markings; the shield-shaped body is about 1/4 inch (5-7 mm) long and about half as wide at the broadest part. Adults may be confused with harlequin bugs, Murgantia histrionica, but are smaller at about 1/3 – 1/5 the size. Eggs are barrel-shaped and deposited singly or in small clusters of about six. Eggs are initially white but turn orange or red prior to hatching. Females lay eggs in the soil beneath host plants but may also oviposit on leaves or on hairy stems of non-host plants. In addition, eggs are often laid on plant protective coverings such as mesh screens or floating row covers. Research suggests that, depending on temperature and food source, a female bug can lay up to 150 eggs within two to three weeks. Eggs can hatch in as little as four days. The nymph passes through five instars. Newly molted nymphs of all stages are orange-red but legs, head, and thorax darken quickly to black. The brightly colored nymphs may be confused with lady beetles but lack their shiny, hardened wings. Older nymphs develop dark wing pads and white spots on the abdomen prior to becoming adults.
The rate of development and number of generations per year is dependent upon climatic conditions and available food plants. In Southern California, there are multiple generations each year and populations generally peak late in summer and fall. All life stages may be present together on plants, especially when pest densities increase, generations overlap, and food sources decrease. Even though Bagrada bugs prefer cool-season cole crops, their development is favored by warmer temperatures. Adults tend to fly when temperatures are above 85°F. Bagrada bugs may hide in leaf litter or topsoil during cool periods and cold winter months.
The Bagrada bug’s main hosts are plants in the mustard family, and it requires these host plants for optimal reproduction. This group includes cruciferous weeds such as various wild mustards, shepherd’s purse, London rocket, and pepperweed. Globally, the Bagrada bug is a serious pest of cole crops — cultivated plants in the Brassica genus such as cabbage, cauliflower, broccoli, kale, turnip, and mustard greens. It also attacks related cruciferous crops such as radish and arugula. Ornamental landscape plants such as alyssum, candytuft, nasturtiums, rockcress, stock, and wallflower can be infested.
Bagrada bugs may become secondary pests of other plant families, particularly when densities are high and crucifers are scarce. For example, it infests weeds such as lambsquarters, purple nutsedge, Euphorbia spp, perennial sowthistle, fleabane, and field bindweed. It causes feeding damage on the fruits of bell pepper, melon, papaya, tomato, and capers. Vegetative and flowering growth of corn, sudangrass, sorghum, sunflowers, potato, cotton, and some legumes, including snap beans, may also be consumed. The Bagrada bug forms large clusters on many different types of plants in the late summer when pest populations are high and food is scarce. When preferred hosts are unavailable, the bug can be found on plants that are not reproductive hosts; and it may or may not attempt to feed. For example, large numbers of Bagrada bugs have been found in Ventura County on strawberry crops but feeding damage has not been reported.
Adults and nymphs of the Bagrada bug feed on leaves, stems, flowers, and seeds. They insert their needle-like mouthparts into plant tissues, inject digestive enzymes, and suck the juices. On leaves and stems, starburst-shaped lesions form. Leaves eventually have large stippled areas and may wilt and die. Ultimately damage may result in “scorched” leaves, stunting, blind terminals, and forked or multiple heads on cauliflower, broccoli, and cabbage. Bagrada bugs are particularly damaging to small plants and may kill seedlings.
Early detection is important because Bagrada bug populations can build up quickly. Levels of infestation may be correlated with proximity to natural and cultivated areas infested with wild mustard or to neighboring vegetable farms. Landscape plants, native plants, and weeds may need to be monitored to prevent pest migration. Bagrada bugs may not be readily observed until damage has begun, so look carefully for fresh feeding damage (light green starburst lesions), which may be easier to spot than the insects themselves at early stages of infestation. Home gardeners and landscapers should carefully inspect their plants and shipping containers prior to planting. A good time to inspect is right after watering when pests hiding in the space between the potting mix and the sides of the container may be flushed out and more easily detected.
When the bugs are common on plants, they may be monitored by beating or shaking plants over a tray or a sheet of paper. More frequent scouting may be necessary when temperatures rise above 75°F. Bagrada bugs tend to be most active and visible during the warmer parts of the day; therefore, monitoring should occur at those times. When temperatures are low or on cloudy days, these bugs may hide on the undersides of leaves, around stem bases, or in soil cracks and crevices.
Remove weed hosts in and near planting areas. Bagrada bug adults, eggs, and nymphs in the soil or container media can be controlled by steam or chemical treatment before planting. Removal of plant residue after harvest can reduce carryover between crops.
In gardens where the Bagrada bug is present in very high densities, it may be advisable to remove very attractive host plants such as sweet alyssum (Lobularia maritima) and replace them with plants not in the mustard family. Sweet alyssum can attract bugs into the garden and also serve as a source of infestation for other plants in the garden or landscape.
Picking the bugs off plants by hand is only feasible if pest populations are very low. When infestations are heavy, it may be possible to vacuum the bugs with a portable vacuum cleaner. It is often easier to tap the plant onto a sheet and collect/vacuum the bugs rather than removing them individually.
Pyramid traps baited with crushed sweet alyssum, inside polypropylene bags, can also be used to catch and destroy bugs, particularly when numbers are high. These traps are available commercially as stink bug traps (e.g., Rescue Stink Bug Trap) but the chemical lures sold to attract other stink bug species will not work against the Bagrada bug.
Growers that have access to greenhouses can protect cruciferous bedding plants and vegetable plugs by producing them inside. Using a double-door system in greenhouses can help to exclude the bugs and screened vents prevent entry of flying adults. As an alternative to greenhouses, screened tunnels or floating row cover fabric can provide plant protection in gardens. The mesh of the screening material must be fine enough to exclude the Bagrada bug nymphs and should be elevated so that it does not touch the plants because the bugs can feed through these coverings. The edges of protective covers must also be buried to prevent the bugs from crawling underneath to the plants, and they must be applied before Bagrada bugs get into the crop.
Although spiders and other general predators may feed on the Bagrada bug, it does not have specific natural enemies in the United States. Stink bugs are so named because they secrete a foul-smelling liquid that is repulsive to many predators. Birds apparently find the taste of these bugs unpleasant and may avoid eating them. Several parasitoids that attack eggs, nymphs, and adult Bagrada bugs are reported in the literature; but thus far, effective biological control organisms have not been available despite the prevalence of this pest in many countries. Unlike the harlequin bug, which it strongly resembles, the Bagrada bug often lays eggs in the soil, which would render egg parasitoids, such as wasps, ineffective. Moreover, although biological control options are currently being evaluated by some researchers, Bagrada bug densities can increase rapidly and biological control alone will probably not keep populations in check.
There is little information on the effectiveness of pesticides that can be used against the Bagrada bug in home gardens. Generally, stink bugs are difficult to manage with insecticides; and repeat applications are often necessary. The adult bugs usually escape injury by flying away before they contact the insecticide only to return later. Home vegetable growers, especially those growing organic crops are likely to have better control using covers or screening to exclude bugs or by simply removing host plants from the garden.
If insecticides are used, check the pesticide label to make sure the product is registered for use on home gardens and landscape plants. Research focused on managing the pest organically on commercially grown cole crops suggests that pyrethrum may suppress adults while azadirachtin and insecticidal soaps may reduce populations of nymphs.
REFERENCES and SUGGESTED READING
Arakelian, G. Bagrada Bug. 2010. Center for Invasive Species Research.
County of Los Angeles Agricultural Commisioner/Weights and Measures. 2008. Bagrada Bug (Bagrada hilaris).
County of Santa Barbara Agricultural Commissioner’s Office. 2012. Bagrada Bug: A New Pest of Cole Crops and Vegetable Gardens in Santa Barbara County.
Dara, S. 2012. Bagrada bug is now in Santa Barbara County.
Halbert, S. E., J. E. Eger. 2010. Pest Alert: Bagrada bug (Bagrada hilaris) (Hemiptera: Pentatomidae) an Exotic Pest of Cruciferae Established in the Western USA . Florida Department of Agriculture and Consumer Services, Division of Plant Industry.
Lawrence, C. 2012. Bagrada bug population explodes at organic farms. Ventura County Star.
Lazaneo, V. 2012. The Bagrada bug: A new pest in San Diego County. San Diego County Master Gardener Newsletter, September. San Diego County Master Gardener Association.
Natwick, E. T., Palumbo, J. and S. Dara. 2013. Bagrada Bug in Agriculture. UC IPM Online, Statewide Integrated Pest Management Program.
Palumbo, J. C. and E. T. Natwick. 2010. The Bagrada bug (Hemiptera: Pentatomidae): A New invasive pest of cole crops in Arizona and California. Online. Plant Health Progress doi:10.1094/PHP-2010-0621-01-BR.
Perring, T. M., Reed, D. A., Palumbo, J. C., Grasswitz, T., Bundy, C. S., Jones, W., T. Royer. 2013. National Pest Alert: Bagrada bug Bagrada hilaris (Burmeister) Family Pentatomidae. 2012. USDA-NIFA Regional IPM Centers.
Reed, D. and T. M. Perring. 2012. Bagrada Bug (Bagrada hilaris): Serious Invasive Pest of Cole Crops and Mustard Greens. .
Reed, D. and T. M. Perring. 2012. Bagrada bug: biology, host range and effects on cole crops. .
Reed, D. and T. M. Perring. 2012. What are those bugs in the alyssum? Retail Nursery and Garden Center IPM News. 2(4): 2.
Reed, D. A., Palumbo, J. C., Perring, T. M. and C. May. 2013. Bagrada hilaris (Hemiptera: Pentatomidae), an invasive stink bug attacking cole crops in the southwestern United States. Journal of Integrated Pest Management. 4(3): DOI:.
Spurrier, J. 2010. Bagrada bug spreads, threatening winter vegetables.
Pest Notes: Bagrada Bug
Authors: D. A. Reed and T. M. Perring, Dept. of Entomology UC Riverside; J. P. Newman, UC Cooperative Extension, Ventura and Santa Barbara Counties; J. A. Bethke, UC Cooperative Extension San Diego and Riverside Counties; J. N. Kabashima, UC Cooperative Extension, Orange and Los Angeles Counties.
Produced by University of California Statewide IPM Program
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