|JONES, S - Tasmanian Institute Of Agricultural Research|
|Gent, David - Dave|
|PETHYBRIDGE, S - Botanical Resources Australia Pty Ltd|
|HAY, F - Tasmanian Institute Of Agricultural Research|
Submitted to: New Zealand Journal of Crop and Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2011
Publication Date: N/A
Interpretive Summary: White mould is one of the most economically damaging diseases of bean. The disease causes losses through reductions in marketable pods, and high levels of the disease can result in complete crop rejection. Management of white mould depends largely on the use of fungicides, although in many instances fungicides may be applied when the disease is not actually a threat to crop yield or quality because of weather or other factors. In this research,we identified factors associated with a high risk of white mould development on pods as a first step towards rationalizing when fungicides would be warranted and also to identify production factors associated with disease outbreaks. We found that the occurrences of white mould on pods could be predicted correctly in 77% of fields based on five relatively simple risk factors. These findings are significant because they point to means to minimize the risk of the disease.
Technical Abstract: In Tasmania, Australia, if more than 5% of bean pods are found to be affected by white mould (caused by Sclerotinia sclerotiorum) entire crops can be rejected by contracting processors. This strict quality standard is one of the main reasons for prophylactic application of fungicides over flowering, although in some instances fields are likely treated when not truly warranted because of low disease risk. In this research, surveys of 109 commercial bean fields were conducted in 2009 and 2010 to identify relationships among edaphic factors, weather variables, and production practices associated the incidence or presence of white mould on pods. Correlations were found between the incidence of diseased pods and the number of apothecia of the pathogen present, timing of the first boscalid application, and mean minimum temperature 10 to 30 days preceding harvest. Significant differences in white mould incidence also were detected among cultivars and bean canopy density. A nonparametric discriminant analysis model based on the predictor variables of mean minimum temperature in the 10 and 30-day period before harvest, cultivar, bean canopy density, and fungicide application correctly predicted whether white mould would occur on pods in 77% of bean fields. This predictive model suggests several factors that can be manipulated to reduce disease risks, and potentially could be used to inform white mould management efforts in bean fields in Tasmania.