Preliminary evaluation of the parasitoid wasp,Collyria catoptron,as a potential biological control agent against the wheat stem sawfly,Cephus cinctus,in North America

The wheat stem sawfly, Cephus cinctus (Hymenoptera: Cephidae) is the major pest of wheat in the northern plains of North America, with biological control providing a potentially useful management tool. Foreign exploration by the USDA-ARS identified Collyria catoptron (Hymenoptera: Ichneumonidae), a parasitoid wasp of Cephus fumipennis in northern China, as a potential biological control agent. Here we carry out a preliminary evaluation of the potential suitability of C. catoptron, as a candidate agent against C. cinctus. Specifically we: (1) Quantify the spatio-temporal variation in parasitism rates on the native host from collection sites in northern China over six years, and (2) Assess whether C. catoptron will oviposit and complete development in the novel targeted host. Maximum parasitism of the native host in the native range was 38%, exceeding the theoretical threshold for successful biological control. Site occupancy levels were high (83%) suggesting good colonisation abilities. C. catoptron clearly recognised and attacked C. cinctus, with parasitism levels exceeding those observed on the co-evolved host C. fumipennis. However, we found no evidence that C. catoptron can complete development in C. cinctus; no adults were reared from this host in either year of the study. In contrast 50–60% of the parasitoids survived to emerge as adults in C. fumipennis. Thus, C. catoptron is unlikely to be a suitable agent against C. cinctus due to basic host incompatibility. Future work will be directed towards developing conservation biological control approaches using native parasitoid species already present in the USA.