Effect of Pupal Cold Storage on Reproductive Performance of Microplitis manilae (Hymenoptera: Braconidae), a Larval Parasitoid of Spodoptera frugiperda (Lepidoptera: Noctuidae).

As a major invasive pest in China, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) has caused great damage to crops. Hymenopteran parasitoids, especially the braconid wasps, play crucial roles in depressing pest populations. However, there was little information about the ideal storage of parasitoids to achieve their mass-rearing. Here, we identified a dominant parasitoid of S. frugiperda , Microplitis manilae (Ashmead) (Hymenoptera: Braconidae), in the Hainan province of China with a field parasitism rate of 5.66-19.10%. The investigation of biological parameters revealed that the parasitism rate of M. manilae significantly decreased with an increase in both wasp adult longevity and host age, and the wasp of 1-3 d post eclosion performed best on the first instar of host larvae, showing the highest parasitism rate. We also discovered that the decreased temperature from 30 to 20 °C greatly extended the longevity of wasp adults, and a similar result was observed after feeding on 10% sucrose water compared with sterile water. Then, the effects of different pupal cold storage temperatures (4 and 10 °C), storage period (prepupa, middle-aged pupa, late-aged pupa) and storage time (5, 10 or 20 d) on the emergence rate, parasitism rate, female proportion and longevity of M. manilae were investigated. The results demonstrated that the middle-aged wasp pupae stored at 10 °C for 5-10 d possessed a stronger parasitic ability and longer longevity. These findings may promote the flexibility and efficacy of large-scale production of M. manilae , thus contributing to its biological field control against S. frugiperda.