When does it pay to apply fungicide to fababeans in Saskatchewan and what does the weather have to do with it
Determine the effect of late season fungicide applications and whether or not these applications will improve/preserve fababean yield and quality. Determine when a second fungicide application may be best in order to improve/preserve fababean yield and quality. Determine if fungicide application timing should be based on visible symptoms and/or weather events rather than growth stage.
A project was conducted during the 2022, 2023, and 2024 season to evaluate different fungicide timings in faba beans at four locations in Saskatchewan. The locations in the study included Agri-ARM sites at Outlook, Yorkton, Melfort, and Scott. The main objectives of the project were to determine the effect of late season fungicide applications, determine when a second fungicide application may be best, and determine if fungicide application timing should be based on visible symptoms and/or weather events rather than growth stage. The 1st experiment consisted of 10 treatments with fungicide applications beginning at the 1st bud stage (R1) and continuing every two weeks until maturation of the faba beans or up to 12 weeks after 1st bud. Among the treatments, two had sequential applications of a fungicide at 2 and 8 weeks after 1st bud and at 2, 6 and 10 weeks after 1st bud. In the 2nd experiment at Melfort only, there were 8 treatments total consisting of a fungicide at 1st detection of disease, 1st flower, and prior to a weather event, along with 3 of the treatments using multiple fungicide applications at 2 weeks after 1st flower and 1st detection and at 1st detection and prior to a weather event. Data collection in both experiments consisted of environmental conditions, growth staging at fungicide applications, disease ratings prior to every fungicide application, days to maturity, grain yield, thousand seed weights and an economic analysis. The conditions of all years were relatively hot and dry during the timing of fungicide applications at all sites (late June to mid-August). Faba bean disease was relatively low at all participating sites in all years, with most sites reporting as little as no disease to as much as 10-20% of the plant infected by foliar lesions at most locations. There were some instances where disease was as high as 30-60%, however, these occurrences were rare, late in the season (near crop senescence), and never resulted in significant yield responses to fungicide. Disease was usually low earlier in the season (late June to mid July) and increased in prevalence as faba beans approached maturity (early to mid August). When disease ratings between treatments were significantly different, the difference between treatments was usually very small (10% or less difference in foliar lesions), and differences often did not occur until later into the season (late July to mid-August). Even when disease ratings were significantly different, they did not translate to a significant yield response. Average yields were nominally often greater with a fungicide application, but yields were not significantly increased from the control. Because yields were often greater, applying a fungicide was often economical, but the general trend was for sites with greater rainfall during flowering to have greater profitability when a fungicide was applied. Furthermore, although faba beans that were sprayed with more than one application of a fungicide often yielded greater, the cost of the second application did not result in enough of a yield response to make a dual application more economical than a single application. When a fungicide application was economical, late applications (late July) often resulted in a positive outcome; however, the result was not greater when compared to an earlier application at each site (late June to early July, depending on site).