Effect of temperature on development and reproduction of Proprioseiopsis asetus (Acari: Phytoseiidae) fed on asparagus thrips, Thrips tabaci

Thrips tabaci Lindeman (Thysanoptera: Thripidae) is one of the most important pests of asparagus in China. In this study the effects of five constant temperatures (15, 20, 25, 30 and 35 A degrees C) on the growth, survivorship and reproduction of Proprioseiopsis asetus (Chant) (Acari: Phytoseiidae) fed on T. tabaci was examined under laboratory conditions. Development time of immatures decreased with increasing temperature. The lower egg-to-adult developmental threshold (T (0)) and thermal constant (K) of P. asetus were estimated at 15.2 A degrees C and 75.8 degree days by means of a linear model. Fertilized females fed on T. tabaci produced offspring of both sexes, whereas the offspring sex ratio [a (TM) Euro/(a (TM) EuroA + a (TM),)] of P. asetus at 20-35 A degrees C was female-biased (0.68-0.78) and not significantly influenced by temperature. Survivorship during immature development was significantly influenced by temperature, and was especially low at 15 A degrees C. Pre- and post-oviposition periods of fertilized females shortened with the increase in temperature. The longest oviposition period was 20.4 days, at 25 A degrees C, whereas at 15 A degrees C the mites did not reproduce. Maximum average life time fecundity and mean daily fecundity was recorded at 25 and 35 A degrees C, respectively; the intrinsic rate of increase ranged from 0.05 (20 A degrees C) to 0.17 (35 A degrees C). The results indicate the capability of P. asetus to develop and reproduce at a broad range of temperatures, especially above 25 A degrees C, which can be used for better management of T. tabaci in asparagus.