BIOLOGICAL-CONTROL OF LOCUSTS AND GRASSHOPPERS USING A FUNGAL PATHOGEN - THE IMPORTANCE OF SECONDARY CYCLING

Persistent chemical pesticides can provide an effective means of contr ol against locusts and grasshoppers due to prolonged activity of the s pray residue. However, use of these pesticides is now prohibited, and nonpersistent chemical alternatives are substantially less successful. Here we show why it is expected that biological pesticides based on t he fungal pathogen Metarhizium flavoviride will be highly effective in the control of both locust and grasshopper. We demonstrate, using nov el population dynamic models containing measured estimates of horizont al transmission coefficients, that secondary cycling of the pathogen a fter a single spray application provides a biological substitute for c hemical persistence. This has significant consequences for the economi cs of biopesticide use in pest control. Furthermore, by identifying th at secondary cycling acts in a density-dependent manner, this study al so highlights fundamental differences between conventional pesticides and biopesticides and how they might be used.