You might not recognize a bagrada bug or see it feeding on your ripening tomatoes, peppers and melons, but the damage is obvious. Bagrada bugs are fairly recent invaders, native to Africa and appearing first in Los Angeles County in 2008.
By 2013, populations had spread to Fresno and Tulare counties. The bagrada bug is a type of stinkbug that feeds primarily on plants on the mustard or brassica family, but when temperatures heat up in early summer and all the mustard family plants turn brown and die, hungry bagrada bugs move into our vegetable gardens.
Bagrada bugs have quickly become serious pests in the central San Joaquin Valley, damaging commercial crops as well as home gardens. Start monitoring for the bugs by looking for the telltale signs of early damage of light-green, star-shaped marks or lesions on the skins of bell peppers, melons and tomatoes. As bagrada bugs suck out the juices of ripening plants, they inject an enzyme into the flesh that causes the lesions. They also feed on the leaves of small plants and seedlings, which first causes leaf spotting and then terminal wilting.
The adult insects which feed during the heat of the day have a shield-shaped body about a quarter-inch long with black, orange and white markings. They resemble harlequin bugs but are smaller in size. They are prolific egg layers. In warm or hot weather, one bagrada female can lay up to 150 eggs over a two- to three-week period.
The eggs can be laid on row covers, in the soil beneath host plants or on hairy plant stems and they hatch within four days. Nymphs look somewhat like lady beetles but without shiny wings.
Control for bagrada bugs is not easy, especially in organic gardens. Biological controls (parasitic wasps) have not proven effective; beneficial predators hate the stinky fluid the bugs produce. The adults fly away when pesticides are applied or when attempts are made to hand pick them. One of their favorite host plants is sweet alyssum, also a member of the mustard plant family and common in Valley home landscapes. Crushed alyssum is used as bait in pyramid traps such as Rescue Stink Bug Trap. Check trap labels; not all stink bug traps will attract bagrada bugs. Remove any sweet alyssum that is surviving the summer heat. Sweet alyssum reseeds vigorously as soon as temperatures cool in early fall. Pull out seedlings if you’ve had problems this summer with bagrada bugs and reconsider planting mustard family crops including broccoli, cabbages and kale this next fall.
Bagrada bug eggs and younger nymphs can be sprayed with pyrethrins. Older nymphs can be controlled with insecticidal soaps.
Increase deep irrigation of citrus trees and mature landscape trees as temperatures climb the next several weeks. Irrigate citrus when the top 4 inches of soil has dried. Plan on weekly irrigation of mature landscape trees during the hottest weeks. Use soaker hoses, bubbler attachments or small oscillating sprinklers to slowly soak the soil over several hours to a depth of at least one foot underneath the edge of the leaf canopy where the small feeder roots lie.
Elinor Teague: firstname.lastname@example.org