Sustainable Controls for Vine Mealybug
The 2006-2010 vine mealybug studies were funded, for one or more seasons, by the American Vineyard Foundation, Central Valley Table Grape Pest and Disease District, California Table Grape Commission, California Raisin Marketing Board, Viticulture Consortium West, and CDFA?s Biological Control Program. Sustainable control research focused on development of a mating disruption program and improving biological controls. The potential for mating disruption was initially studied from 2004-2006, with field experiments located in the Central Valley, the Northern Interior Winegrape region, and the Central and Northern Coastal Winegrape regions. Results showed mating disruption, in combination with an in-season insecticide, often reduced numbers of pheromone trap catches (adult males) and crop damage. Development of a commercial program was studied in 2007 and 2008, after which we successfully wrote a Section 18 to allow the commercial sale of mating disruption. In the 2009 and 2010 seasons, we investigated the use of mating disruption with reduced insecticide use. Results suggest mating disruption can be a part of sustainable mealybug control. Keys to its success include pre-conditioning the vineyard to lower mealybug density (e.g., insecticides), multi-year applications of dispensers, early dispenser deployment (e.g., typically May), in-season insecticide applications as needed, and management practices that promote natural enemies. Understanding and improving biological controls of vine mealybug began in 2003, with surveys of resident natural enemies. In 2005, we released commercially available parasitoids from Europe (Leptomastidea abnormis and Leptomastix dactylopii). In 2005, we also began foreign exploration and importation of parasitoids, eventually collected material in the Mediterranean (Spain, Portugal, France, northern Italy, and Sicily), Middle East (Israel, Egypt and Iran), and South Africa. In 2006 and 2007 studies focuses on production and release of A. pseudococci (from northern Italy) and Coccidoxenoides perminutus (from South Africa); ~75,000 A. pseudococci and ~500,000 C. perminutus were released in California vineyards. Recoveries of these parasitoids suggest all four species have established in California vineyards, with A. pseudococci the most important species. In 2009 and 2010, studies investigated A. pseudococci geographic strains, with molecular work showing distinct separation of populations (e.g., eastern Spain compared with Israel). Observations in the insectary and field cage studies suggest that A. pseudococci material from Spain may be best able to suppress vine mealybug populations in California. This parasitoid material has recently been released to commercial insectaries for greater statewide distribution. In 2009 and 2010, we investigated the combined use of mating disruption and biological controls. Studies in commercial vineyards showed little impact of parasitoids, in part, due to low mealybug densities and the use of non-selective insecticide materials. Field studies showed no increase in parasitism on vines with a mating disruption dispenser.