Population Dynamics of the Vine Mealybug and its Natural Enemies in Coachella and San Joaquin Valley Grape Growing Regions
The vine mealybug (VMB) was first identified as a new pest in the Coachella Valley (CV) and shortly thereafter moved north into the San Joaquin Valley (SJV). We report on VMB population dynamics and parasitoid effectiveness in these two different regions. In CV vineyards, VMB density followed a well-known pattern, increasing from spring through early summer, followed by a dramatic decline in May and June. Two parasitoids were recovered ? Anagyrus pseudococci and Leptomastidea abnormis. Both parasitoids increased with VMB densities, however, Anagyrus appeared before Leptomastidea. In SJV vineyards, VMB similarly concentrated on the lower trunk and roots in winter and progressively moved from these protected areas during spring. However, comparison of CV and SJV data showed important differences in VMB seasonal abundance, distribution, and parasitism. In CV, there were 2 distinct adult VMB peaks, while 3 occurred in SJV ? with adult and crawler densities highest in June. In SJV there were also all VMB life stages found on roots, trunk, canes, leaves and fruit in summer and fall samples. Factors leading to VMB decline most sharply contrast the 2 regions. In SJV samples, Anagyrus killed >80% of exposed VMB by August, resulting in lower VMB densities (Leptomastidea was not recovered). Parasitism in the CV never exceeded 25%, and VMB decline came 2 months earlier and was more clearly associated with increasing temperatures than parasitism. The more exposed locations of VMB (e.g., leaves) in the SJV may have resulted in higher parasitism. Laboratory studies on VMB and parasitoid biology are being conducted.
