January 30, 2015
California finds itself concerned with a new exotic pest about six times each year, according to the University of California Cooperative Extension, the community outreach arm of the University’s Division of Agriculture and Natural Resources. Whether a plant, insect or pathogen, these foreign “hitchhikers” are without the natural enemies that keep them under control in their native territories, thus they have the capacity to wreak havoc on our agricultural, native and urban environments, not to mention your garden.
The bagrada bug (Bagrada hilaris) is one of these invaders. A native of Africa, this nasty little bug was first sighted in California in Los Angeles in 2008, and is slowly marching northward.
The shield-shaped bagrada bug is a relative of the much-larger brown marmorated stink bug. But because of its distinctive black color with orange and white marking, it is sometimes confused with the harlequin bug, a common American species. But bagrada is much smaller, only about ¼-inch long, and has subtle white markings that the harlequin lacks. Eggs, laid singly or in clusters, are barrel shaped, initially white and turning orange to red right before hatching. Newly molted nymphs of all stages are orange to red with legs, head and thorax that quickly darken to black. Don’t confuse these young bagrada bugs with beneficial lady bugs.
The bagrada bug loves edibles in the mustard (Brassicaceae) family, such as cabbage, cauliflower, broccoli, Brussels sprouts, radishes, rutabaga and kale, but it will also feed on related ornamentals such as stock, sweet alyssum and nasturtiums, as well as grasses and weeds such as wild mustard and Bermuda grass. These insects have needle-like mouth parts that they insert into plant tissues, inject digestive enzymes and suck the juices. They go after leaves, stems, flowers and seeds, particularly damaging small plants and killing seedlings.
The bagrada bug overwinters in the adult stage and lays eggs in the spring through early fall. They may shelter indoors during colder weather. Outside, begin to watch for bagrada bugs and their nymphs when temperatures reach 75 degrees. It’s best to monitor for these insects in the morning, after a day where temperatures have reached 85 degrees, as you may actually see them grouped together close to the bottom of the plant near or on the soil. The damage can be easier to spot than the insects themselves. Look for light green star-shaped lesions that bleach out over time.
It may be inevitable that the bagrada bug will invade Marin, and early detection is so far the best weapon in the arsenal of defenses. Closely inspect susceptible plants and their containers prior to purchase, transportation or 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. Try shaking your plant over a tray or sheet of paper and see what falls out. And look for those tell-tale lesions.
According to UC’s Center for Invasive Species Research, as of last October, bagrada bugs have yet to be seen in Marin in any significant numbers, but they have impacted 22 other California counties, some close by. So Marin needs to be on the lookout.
If you suspect you have found a bagrada bug, place it in a sealed jar, note where and when you collected it and bring it to the Master Gardener Help Desk at the UC Cooperative Extension office, 1682 Novato Blvd. Suite 150B in Novato, or the Department of Agriculture, Weights and Measures office next door.
For more information on the bagrada bug and what can be done to control it, check out UC’s Integrated Pest Management website at www.ipm.ucdavis.edu.