Why two species of parasitoids showed promise in the laboratory but failed to control the soybean aphid under field conditions

Abstract

Following the rapid spread of soybean aphid, Aphis glycines in North America in the early 2000’s, biological control was identified as a cost-effective approach for management of this invasive pest. Two parasitoid species, Binodoxys communis and Aphidius colemani, were considered as potential candidates for classical and inundative biological control, respectively. The objectives of the present study were to determine the overwintering capacity of B. communis under climatic conditions prevailing in northeastern North America, and to measure parasitism and dispersal capacity of A. colemani when released in soybean fields. Field and laboratory assessments showed that the Chinese strain of B. communis, Harbin 2002, has a very poor capacity to enter into diapause (<0.8%), and thus to establish in North America. We suggest that this strain has gradually lost its ability to enter diapause during the extended periods of quarantine and laboratory confinement, during which it was continuously exposed to non-diapause rearing conditions. A.colemani did not show strong potential to control A. glycines. Following the release of approximately 8400 females in experimental plots, only 113 mummies were recovered within a radius of 60m from the release point. Although both parasitoids were promising in controlled environments, the B. communis Harbin 2002 strain and the A. colemani commercial strain did not show strong potential to control A. glycines populations in soybean fields.