Safety zones for a Sclerotinia sclerotiorum-based mycoherbicide: Accounting for regional and yearly variation in climate

Abstract

Variation in the width of ‘safety zones’ for sheep and dairy pasture treated with a Sclerotinia sclerotiorum (Lib.) de Bary-based mycoherbicide was quantified using 10 years of climate data from each of five regions in New Zealand. Acceptable and risk-averse zones were defined as the maximum distances in any direction from a treated pasture where ‘added:natural’ ratios of air-borne S. sclerotiorum spores are 1:1 and 1:10, respectively. The 10-year mean 1:1 safety zone had zero width for sheep pasture at all locations, and was at most, 50 m wide for dairy pasture. The width of the 10-year mean 1:10 zone varied regionally from 314 to 443 m for sheep and from 175 to 280 m for dairy pasture, and the 90th percentile 1:10 zones were up to 41% wider. Linear relationships between safety zone width and mean wind speed were evident and these could be used to derive region-specific safety zones.

Keywords:

• Atmospheric dispersion
• biological weed control
• Cirsium arvense
• Gaussian plume model
• Ranunculus acris
• risk analysis

Acknowledgments

We thank the New Zealand Foundation for Research, Science and Technology for funding this project and Chris Hunt, AgResearch, New Zealand, for Figure 2. We also thank: Dave Saville, AgResearch, New Zealand; Hans Erbrink, KEMA Power Generation and Sustainable, Arnhem, The Netherlands; Jan-Carel Zadoks, Amsterdam, The Netherlands; Donald Aylor, Connecticut Agricultural Experiment Station, USA; James Powell, Department of Mathematics and Statistics, Utah State University, USA, and Jan Goudriaan, Plant Production Group, Wageningen University, The Netherlands, all of whom have contributed greatly to the development of the concepts and models implemented in this analysis.