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 °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 °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 [♀/(♀ + â™‚)] of P. asetus at 20-35 °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 °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 °C, whereas at 15 °C the mites did not reproduce. Maximum average life time fecundity and mean daily fecundity was recorded at 25 and 35 °C, respectively; the intrinsic rate of increase ranged from 0.05 (20 °C) to 0.17 (35 °C). The results indicate the capability of P. asetus to develop and reproduce at a broad range of temperatures, especially above 25 °C, which can be used for better management of T. tabaci in asparagus.

[Control efficacy of Trichogramma japonicum against Chilo suppressalis and Chilaraea auricilia].

In order to understand the relationships of the population increase capacities between egg parasitoid Trichogramma japonicum Ashmead (Hymenoptera: Trichogrammatidae) and two rice borers Chilo suppressalis Walker and Chilaraea auricilia Dudgeon (Lepidoptera: Pyralidae), and to evaluate the control efficacy of T. japonicum against C. suppressalis and C. auricilia, life table method was adopted to establish the experimental population life tables of the two rice borers and the population fecundity tables of T. japonicum on the two hosts, and to estimate the fecundity and parasitism capacity of T. japonicum on the two hosts. The generation period (T) of C. suppressalis and C. auricilia was 56.40 d and 47.80 d, and their intrinsic rate of natural increase (r(m)) was 0.0489 and 0.072; while the T of T. japonicum on C. suppressalis and C. auricilia was 9.75 d and 9.78 d, and the r(m) was 0.3154 and 0.3161, respectively. These parameters indicated that T. japonicum could control the two rice borers effectively.