Effect of Short-Term Low Temperature on the Growth, Development, and Reproduction of Bactrocera tau (Diptera: Tephritidae) and Bactrocera cucurbitae.

The fruit flies Bactrocera tau (Walker) and B. cucurbitae (Coquillett) are economically important invasive pests on numerous vegetable and fruit species in China. Due to the instability of the early spring climate, temperatures often deviate far below the normal temperature for short periods of time. Such a sudden short-term low temperature may impact the reproduction and development of the two fruit fly species. In this study, the effects of low temperatures (8, 6, 4, 2, 0, -2, and -4°С) on the development and reproduction of these two closely related fruit fly species were studied under laboratory condition. The results showed that their survival rates decreased gradually with corresponding decreases in the tested temperatures. On the other hand, their pre-oviposition periods and their adult female to male sex ratios increased, while the average number of eggs per female of each species and longevity of male adult of B. cucurbitae initially increased and later decreased after exposure to the low-temperature treatments. Overall, low temperatures promoted reproduction in B. cucurbitae and B. tau at temperatures ranging from 24°С to as low as 8°С. Development and reproduction of the two species were negatively affected when temperatures were between 8 to -4°С. The cold resistance of each developmental stage was higher in B. tau than in corresponding stages of B. cucurbitae.