Impact of forecasting system, biological control agent and fungicide application on white mould of dry bean and canola

Project code: PRR03-380

Project Lead

Debbie McLaren - Agriculture and Agri-Food Canada

Objective

To integrate different approaches including forecasting, cultural controls, and biopesticides for the management of sclerotinia disease in dry bean and canola

Summary of Results

The effectiveness of Coniothyrium minitans, an indigenous mycoparasite, as a biocontrol agent for sclerotinia diseases (Sclerotinia sclerotiorum) of bean (Phaseolus vulgaris) and canola (Brassica napus) was evaluated in two provinces, Manitoba and Alberta, during 2004-06. Two bean cultivars (NW63 and Envoy) at two seeding rates were used at the Manitoba sites while one cultivar (NW63) and one seeding rate were used at the Lethbridge site. In bean tests, the application of C. minitans significantly reduced the incidence of white mould and the number of sclerotia of S. sclerotiorum in harvested seed, and increased infection of sclerotia produced on diseased plants. White mould incidences were lower in the upright bean cultivar Envoy in comparison to the viny cultivar NW63 at the majority of sites. Use of a lower seeding rate did not significantly reduce white mould of bean; however, over all sites and years, a numerical trend of less disease at the lower seeding rate was frequently observed. In canola trials, C. minitans was also effective in reducing the incidence of sclerotinia stem rot. Over the 12 site years, seeding rate had a significant impact on stem rot in 5 of the site years, with less disease at the lower seeding rate. C. minitans applied as a foliar spray, as a soil amendment or as a combination of foliar spray plus soil amendment, as well as fungicide (boscalid) spray, all significantly reduced incidence and severity of stem rot of canola and white mould of bean at the Lethbridge site. The suppression of sclerotinia disease in the combined treatment of C. minitans foliar spray plus soil amendment was similar to that of the fungicide treatment, and both treatments resulted in the highest seed yields at Lethbridge. This study indicates that cultivar selection and seeding rate can be important management tools for sclerotinia disease. Application type such as foliar, and soil+foliar can also be important in managing losses from Sclerotinia sclerotiorum in both bean and canola. The forecasting system, using the spray advisory model in combination with soil moisture values and crop development stage, was able to predict periods where conditions were favourable for disease development, and often improved control. This system utilized the risk of apothecial production as an indicator of the probability of development of white mould in bean. "Ground truth" validation of the forecasting system is required for further assessment of this tool for managing sclerotinia disease and to determine if further adjustments are necessary.

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