New pest targets cole crops, worries farmers
Updated: Friday, January 28, 2011 11:38 AM
Bagrada bugs suspected of stowing away in bins, trucks
By CECILIA PARSONS
For the Capital Press
A pest that cole crop growers in the Southwest have battled for the past two growing seasons has inched its way north.
The first bagrada bug was found in Kern County earlier this month. County entomologist David Havilland found the brightly colored stink-bug-styled pest in a Napa cabbage field near Buttonwillow, Calif. Finding the bagrada bug had invaded the county was not a shock, Havilland said.
"It's been moving around. It can live anywhere cole crops are grown," he said.
Agriculture officials and growers on California's Central Coast and in Monterey County are on the look out for the bagrada bug, which can decimate cole crops and other brassicas.
Bagrada bugs can be managed by pyrethroid insecticides, but there are no organic treatments and organic growers could face major challenges if the pest moves into their fields, Havilland said. Backyard and community gardens where pesticides are not used could become infested this spring.
The bagrada bug, also known as the painted bug due to the orange markings on its back, was first found in June 2008 in Los Angeles and Orange counties. By fall 2009, it was found in Imperial County, the Coachella Valley and near Yuma, Ariz., where growers have had 50 percent crop losses in organic fields and up to 20 percent losses in conventionally farmed fields.
Adult and nymph bagrada bugs suck sap from young leaves, and the feeding causes large white patches or wilted areas on leaves. In cases of heavy infestations, the feeding can stunt the central heads. According to university researchers, infestations can build rapidly where there is no chemical control. There is no known biological control or parasitoids that attack eggs, nymphs or adults.
Cabbage, kale, turnip, cauliflower, mustard, broccoli and radish are the main crops it attacks, but it can also be found in potato, cotton, capes and some legumes. Weed hosts include field bindweed, purple nutsedge, lambsquarter, black mustard and perennial sowthistle. Havilland said spread of the pest from the southwest to Kern County was natural since it thrives were cole crops are cultivated. It could have hitchhiked north on bins, trailers and other harvest and cultivation equipment, he said.
Adult bagrada bugs are 5 to 7 millimeters long with black, shield-shaped bodies. There are distinctive orange and white markings on their backs. Female bagrada bugs, which are larger than males, can lay as many as 100 eggs within two to three weeks. Eggs are laid on leaves and in the soil under plants. The incubation period is four to eight days. Usually all live stages are present on plants.
The bagrada bug is native to Africa, India and Pakistan and is also found in southern Europe and Egypt.
It is listed as an invasive species by the Center for Invasive Species Research at University of California-Riverside.