Sublethal effects of pyridalyl on the development and reproduction of Plutella xylostella
Author of the article:JIA Bian-Tao** YAN Kun ZHONG Jing-Yin HU Xi-Chao JIA Dong***
Author's Workplace：Shanxi Key Laboratory of Bioagent Utilization and Eco-Pesticide Innovation, College of Plant Protection, Shanxi Agricultural University, Taigu 030801, China
Key Words：Plutella xylostella; pyridalyl; toxicity; sublethal effect; population parameters
Abstract：[Aim] To investigate the sublethal effects of pyridalyl on Plutella xylostella and thereby provide useful information for the control of this pest and the rational application of pyridalyl. [Methods] The toxicity of this insecticide to 3rd instar P. xylostella larvae was determined using the leaf dipping method. Larvae were treated with two sublethal concentrations, LC10 (1.56 mg/L) and LC25 (4.37 mg/L), and the effects of these treatments on their growth, development, and other population parameters, were analyzed using life tables for each sex. [Results] Sublethal concentrations of pyridalyl significantly reduced larval survival, pupation, and emergence, rates, and also reduced pupal weight (P < 0.05) in a dose dependent fashion. The cumulative pre-pupal mortality rate reached 68.50% in the LC25 treatment group. The duration of the period from the 3rd instar to pupation, the pupal stage, and the pre-adult period, were significantly prolonged (P < 0.05). The duration of the period from the 3rd instar to pupation, and the pre-adult period, of the LC25 treatment group were 68.6% and 47.5%, respectively, longer than those of the control group. The lifespan of male and female adults in the LC25 treatment group were significantly shorter, and a lower the proportion of females entered eclosion, compared to the control group (P < 0.05). Neither treatment significantly affected the number of eggs laid per female or the hatching rate, but both delayed the peak of reproductive activity. The net reproductive rate (R0), intrinsic growth rate (rm), and finite rate of increase (λ) of the population were significantly lower (P < 0.05), whereas the generation period (T) was significantly prolonged (P < 0.05). R0 of the LC25 treatment group (5.41) was 82.1% less that of the control group (30.30). [Conclusion] Sublethal concentrations of pyridalyl can significantly inhibit the development and population growth of P. xylostella. The results provide useful information for regulating P. xylostella populations with sublethal doses of pyridalyl, and for the rational rotation of pyridalyl with other pesticides.