Functional response and mutual interference of Peristenus spretus (Hymenoptera: Braconidae), a parasitoid of Apolygus lucorum (Heteroptera: Miridae)

Abstract

Peristenus spretus Chen & van Achterberg (Hymenoptera: Braconidae) is a solitary endoparasitoid, which is considered for augmentative biological control of Apolygus lucorum Meyer-Dür (Heteroptera: Miridae) in Chinese cotton fields. Since the association of P. spretus with A. lucorum was only recently discovered, the biology of the parasitoid remains unknown. In order to understand its reproductive biology, the mutual interference and functional response of P. spretus were investigated by altering either the parasitoid or the host density while keeping the other constant. In both experiments, the effects of parasitoid and host densities on parasitism, superparasitism, progeny production and sex ratio were assessed. P. spretus exhibited a Holling type II functional response to changing host densities, indicating that parasitism increases with increasing host density until the parasitoid reaches its maximum reproductive capacity. The model suggested that a single P. spretus female could parasitise a maximum of 88 nymphs per day or four nymphs per hour. Increasing the wasp-nymph ratio from 1:10 to 1:80 significantly increased the offspring production more than fivefold from ±5.8 to ±35.6; further increasing the host densities (above 80 nymphs) did not significantly increase offspring production. Strong mutual interference of foraging P. spretus females occurred only at high parasitoid densities. Parasitoids foraging alone produced an average progeny of 33.4, whereas parasitoids foraging in groups of 16 produced only 2.6. The optimal wasp-nymph ratio for mass-rearing P. spretus is 4:100, given that resources of parasitoids and nymphs are unlimited.

Keywords:

• Peristenus spretus
• Apolygus lucorum
• functional response
• mutual interference
• superparasitism
• sex ratio

Acknowledgements

We thank Feng Zhong and Xuehua Xie (Hunan Agricultural University, Changsha, China) for their assistance during the experiments. We are grateful to C. van Achterberg (National Natuurhistorisch Museum, Leiden, The Netherlands) and Xuexin Chen (Zhejiang University, Hangzhou, China) for identifying parasitoids and S. Toepfer and S. Abdallah (CABI Europe - Switzerland) for reviewing and editing the manuscript. This research was supported by the National Key Basic Research Program of China (2013CB127602), the Special Fund for Agro-scientific Research in Public Interest of the Ministry of Finance of China (201103012), China's donation to the CABI Development Fund and Science Fund for Creative Research Groups of the National Science Foundation of China (31321004).