Predicting field diseases caused by Sclerotinia sclerotiorum: A review

Predicting diseases caused by Sclerotinia sclerotiorum in field crops remains difficult, and published literature is largely inconsistent in finding significant relationships with environmental and agronomic factors for various life stages of the fungus. A scoping review was performed to synthesize the current quantitative insights into the role of the environment on the life cycle of S. sclerotiorum and the relationships between various life stages of the fungus and final disease expression under field conditions. For most variables, relationships with stages of the life cycle showed a wide range of responses ranging from closely related (high correlations or r(2) values) to not related at all. The effects were often moderated by year, location and/or the presence of another variable such as irrigation, soil type, row spacing or cultivar. Studies that based analysis on a more nuanced understanding of pathogen biology rather than looking only at linear relationships tended to find stronger associations between variables. Yield was consistently negatively associated with disease levels, but cultivar, year, location and planting density were all important determinants of yield. Suggestions for improvement to future research in predictive model development of S. sclerotiorum diseases are discussed.