"This increase means that now there are reproducing, self-sustaining populations of flies spreading across the four sites, beyond their original release boundaries. Counting galls is the best way to measure the population density of these ¼-inch long insects. Since 2018, the number of Cape-ivy galls has multiplied by up to 40 times at these four locations each gall indicating a place where a female fly has laid her eggs. Moran and Portman found the shoot tip-galling fly is reproducing rapidly at Coast Dairies State Park, Garrapata State Park, Glen Deven Ranch and the San Luis Obispo Land Conservancy. Field observations in South Africa confirmed that this fly attacks no other plant species but Cape-ivy. Before the fly was released in California, now retired ARS research entomologist Joe Balciunas tested the fly against 99 other plant species to ensure it would not harm wild native and crop plants in California. Its frequency there is limited in part because of natural insect enemies, including the shoot tip-galling fly. Although it belongs to the sunflower plant family, it is aptly nicknamed the "kudzu of the west."ĪRS scientists have established a reproducing population of shoot tip-galling flies at Glen Deven Ranch (Big Sur Land Trust) as a biocontrol for Cape-ivy, one of the top ten worst invasive weeds in California.Ĭape-ivy is native to South Africa, where it inhabits coastal sites and mountain forests. It forms impenetrable mats and climbs to drape trees and shrubs. In California alone, Cape-ivy covers more than 500,000 acres, often invading areas unsuitable for chemical or mechanical control. It smothers and displaces native plants, clogging water flow along stream banks, interfering with flood control and consuming valuable water resources. Additional releases have been made in southern California through a collaboration with researchers at the University of California-Santa Barbara.Ĭonsidered one of the top ten worst invasive weeds on the West Coast, Cape-ivy has invaded coastal habitats from California to Oregon. Since 2016, more than 5,000 shoot tip-galling flies have been released through the ARS research program. Research entomologist Patrick Moran and entomologist Scott Portman, with the ARS Invasive Species and Pollinator Health Research Unit in Albany, California, have been releasing the shoot tip-galling fly ( Parafreutreta regalis) at 18 locations along the coast, from Humboldt county in northern California to San Luis Obispo in central California, in hopes of developing a self-sustaining control for Cape-ivy. ARS First Biocontrol Galling to Cape-Ivy, a Top Ten Noxious Weed on West CoastĪLBANY, CALIFORNIA, November 9, 2020-Agricultural Research Service scientists have confirmed a biocontrol insect they have been releasing to fight the invasive weed known as Cape-ivy has become established in at least four locations along the California coast.