Sublethal impact of paraquat on the life span and parasitic behavior of Diaeretiella rapae M’Intosh

Abstract

This study focuses on assessing the impact of sublethal doses of paraquat on the survival, the emergence, the life span and the parasitic behavior of Diaeretiella rapae M’Intosh (Hymenoptera: Braconidae). The impact of sublethal doses was measured at room temperature using different densities of the cabbage aphid Brevicoryne brassicae. The results reveal that the field dose of paraquat caused 100% mortality in D. rapae. The percentage emergence of D. rapae decreased from 80.5% in the control group to 71.5% when treated with the lowest concentration of paraquat. Similarly, the life span of parasitoids that emerged from the mummy treated with paraquat also decreased significantly. Oviposition capability and ovipositor thrusting frequency of D. rapae also treated with sublethal dose paraquat decreased significantly along with a shortened patch residence time in the foraging area.

Keywords:

• Toxicity
• functional response
• herbicide
• natural predator
• biological control

Acknowledgments

This research was funded by the Yunnan Provincial Natural Science Foundation (2010CD051), National Natural Science Foundation (51166014) and MISEREOR grant (335-031-1015Z) “Facilitating Community Driven Sustainable Development.” The authors would like to thank Rajesh Daniel, Logan Fitzpatrick and Peter Micic for their editorial assistance. An early draft of this manuscript was presented at the 13th World Lake Congress Wuhan, China in Oct., 2009.