Effect of Spodoptera litura Eggs on Parasitism in Telenomus remus Under Different Refrigerated Conditions

Objective Telenomus remus is the dominant egg parasitoid of Spodoptera frugiperda, and Spodoptera litura is an excellent host for the reproduction of T. remus. The study was conducted to clarify the effects of refrigeration temperature and duration of S. litura eggs on the reproductive ability of T. remus, which would provide references for the biological control of S. frugiperda.

Method Different refrigeration temperatures (4, 8, 12 ℃) and durations (0, 3, 6, 9, 12 d) were designed to refrigerate the eggs of S. litura for the parasitism of T. remus, the effects of parasitism rate, emergence rate and female ratio of T. remus were analyzed.

Result The results showed that both the refrigeration temperature and duration of S. litura eggs could significantly affect the parasitism rate, emergence rate and female ratio of T. remus (P < 0.01). Overall, with the decrease of refrigeration temperature and the prolongation of refrigeration duration of S. litura eggs, the parasitic reproduction indicators of T. remus showed a downward trend. The most suitable refrigeration condition were obtained at 8 ℃ or 12 ℃ for 3 d, which had no significant effect on T. remus reproduction compared with the control (P > 0.05). The parasitism rate, emergence rate and female ratio of S. litura eggs were 85.98%, 94.71%, 56.15% (8 ℃, 3 d) and 85.49%, 94.61%, 60.00% (12 ℃, 3 d), respectively. It had a significant effect on the parasitism of S. litura eggs when the eggs were refrigerated at 12 ℃ for 6 d or 9 d (P < 0.05). The parasitism and reproduction of T. remus were affected to a certain extent, but it could still maintain the normal reproduction of the population, which could be used as an alternative refrigeration condition for S. litura eggs. It also had a significant effect on the parasitism of S. litura eggs (P < 0.05) when the eggs were refrigerated under other conditions which should not be considered as suitable refrigeration condition for the eggs of S. litura.

Conclusion For short-term refrigeration, the condition at 8 or 12 ℃ for 3 d is recommended for S. litura eggs; while for longer duration, 12 ℃ can be selected, but the refrigeration time should not exceed 9 d.