Thermal Tolerances of the Spotted-Wing Drosophila Drosophila suzukii (Diptera: Drosophilidae)

The spotted-wing drosophila (Drosophila suzukii Matsumura) is an invasive species of Asian origin that is now widely distributed in North America and Europe. Because of the female's serrated ovipositor, eggs are laid in preharvest fruit, causing large economic losses in cultivated berries and stone fruit. Modeling D. suzukii population dynamics and potential distribution will require information on its thermal tolerance. Large summer populations have been found in regions with severe winter conditions, though little is known about responses to prolonged low-temperature exposure. We used controlled chambers to examine D. suzukii fecundity, development rate, and mortality across a range of temperatures encompassing the upper and lower thresholds (5-35A degrees C). Optimal temperatures (T-opt) were found to be 28.2A degrees C for the development of the egg-to-adult stage, and 22.9A degrees C for reproductive output. No adult eclosion occurred below 8.1A degrees C (T-lower) or above 30.9A degrees C (T-upper). We also investigated survival outcomes following prolonged (42-d) low-temperature exposure to a simulated cold winter (-5, -3, -1, 1, 3, and 5A degrees C). Adult survival was dependent on temperature, with a mean LT50 of 4.9A degrees C. There were no effects of sex, mating status, geographic strain, and photoperiod preexposure on overwintering survival. Thirty-eight percent of females that were mated prior, but not after, prolonged low-temperature exposure produced viable offspring, suggesting that this species may undergo sperm storage. This study provides data on the thermal tolerances of D. suzukii, which can be used for models of D. suzukii population dynamics, degree-day, and distribution models.