Biosafety concerns on the use of Photorhabdus luminescens as biopesticide: experimental evidence of mortality in egg parasitoid Trichogramma species.

摘要

P. luminescens, a symbiotic bacterium associated with the entomopathogenic nematode Heterorhabditis indica, has recently been shown to exhibit biopesticidal potential against important pests, independent of its host nematode. The bio-ecological compatibility of the bacterium was evaluated in vitro against 2 species of the common biological control agent Trichogramma (T. chilonis and T. japonicum) in their hyperparasitized form inside the host eggs of the rice grain moth, Corcyra cephalonica. In 65% of the eggs exposed to P. luminescens cells alone or their toxins, the C. cephalonica egg shells became flaccid and a significant reduction of up to 84% in the emergence of Trichogramma adults was observed. The possible access of bacterial cells or their secreted toxins to the Trichogramma embryo sheltered inside the C. cephalonica egg shell is discussed. H. indica carrying the bacterium within its gut had no effect on the emergence. The results point to the bio-ecological hazards of the indiscriminate use of P. luminescens as a biopesticide. Due to its wide host range, the inclusion of P. luminescens in any integrated pest management programme should be monitored until proven safe for natural enemies and nontarget organisms..