As part of an ongoing foreign exploration and importation initiative for vine mealybug, Planococcus ficus Signoret, parasitoids have been collected in the Mediterranean regions of Europe, northern Africa, and South Africa. Natural enemies were either sent first to the USDA-ARS laboratory in France, and then to the UC Berkeley Quarantine Facility (collections by Sforza) or sent directly to UC Berkeley Quarantine (collections by Daane). Our goals were to screen the imported natural enemies for their potential to lower mealybug populations in California, and for their possible non target impacts. In 2008, new material was collected in Spain, and a colony has been established in Quarantine. This material will undergo screening in 2009.
In 2008, releases of A. pseudococci and C. perminutus were made in vineyards the in San Joaquin Valley (SJV), the Northern Interior Winegrape Region (Sacramento and San Joaquin Counties), the North Coast (Sonoma and Napa Counties), and Central Coast (San Luis Obispo County) regions. There were nearly 54,000 female A. pseudococci produced and released, in both open-air and caged vine trials. A. pseudococci ?northern Italy? was produced in the UC Berkeley Insectary (12,200 females released) as well as the commercial ?Sterling Insectary? (36,100 females released). Field production of the A. pseudococci Sicily strain was directed from CDFA (5650 females released). From April to October, 2000-3000 female A. pseudococci per acre were released in the coastal plots, and ca. 700 females were released per acre in the interior plots. The more easily reared C. perminutus, of which 51,600 adults were released, were produced at the UC Berkeley Insectary. To date, we have recovered A. pseudococci at all sites, however, we have not yet completed the molecular work on samples to determine if the recovered material was from our release (northern Italy) or the A. pseudococci strain resident in California (Israel). We have recovered C. perminutus from all regions, but not from all sites.
Field cage studies show that combinations of the natural enemies tested (Anagyrus pseudococci, Coccidoxenoides perminutus and Cryptolaemus montrouzieri) most often work better than these species released as a monoculture. Field cage studies also suggest higher levels of parasitism and better levels of mealybug reduction when the mealybug sex pheromone was applied.
Molecular studies on vine mealybug have been completed and indicate that the material present in California and Mexico originated from Israel. Furthermore, there may be large enough differences between the European and Israel/California populations that biological difference may exist which will change the levels of damage and population sizes in the field, as well as control option. Current work is focusing on molecular difference in parasitoid populations.