Prospective analysis of the invasive potential of the European grapevine moth Lobesia botrana (Den. & Schiff.) in California

1 The polyphagous European grapevine moth Lobesia botrana (Den. & Schiff.) is the principal native pest of grape berries in the Palearctic region. It was found in Napa County, California, in 2009, and it has subsequently been recorded in an additional nine counties, despite an ongoing eradication programme. The present study aimed to assess prospectively its potential geographical distribution and relative abundance in California and the continental U.S.A. A subsidiary goal was to provide explanation for timing control measures. 2 Data from the European literature were used to formulate and parameterize a holistic physiologically-based demographic model for L. botrana. This model was linked to an extant mechanistic model of grapevine phenology, growth and development that provides the bottom-up effects of fruiting phenology, age and abundance on L. botrana dynamics. Fruit age affects larval developmental rates, and has carryover effects on pupal development and adult fecundity. Also included in the model were the effects of temperature on developmental, survival and fecundity rates. 3 Observed daily weather data were used to simulate the potential distribution of the moth in California, and the continental U.S.A. The relative total number of pupae per vine per year was used as the metric of favourability at all locations. The simulation data were mapped using grass gis (). 4 The model predicts L. botrana can spread statewide with the highest populations expected in the hotter regions of southern California and the lower half of the Central Valley. In the U.S.A., areas of highest favourability include south Texas, and much of the southeast U.S.A. 5 The effects of a warmer climate on pest abundance were explored by increasing observed mean temperatures 2 degrees and 3 degrees C. L. botrana abundance is expected to increase in northern California and in the agriculturally rich Central Valley but to decrease in the hot deserts of southern California where summer temperatures would approach its upper thermal limit. 6 Analysis of the timing of mating disruption pheromone for control of L. botrana suggests the greatest benefit would accrue by targeting adults emerging from winter diapause pupae and the flight of first summer adults.