Evaluation of combined fungicide and genetic resistance to control white mold in green beans (2016)

Research report to the Oregon Processed Vegetable Commission

PI Jim Myers
OSU Dept. of Horticulture

Co-PI Ed Peachey
OSU Dept. of Horticulture

Executive Summary

The resistance to white mold obtained so far in snap beans has been derived from NY 6020, which provides partial physiological resistance. Under light disease pressure, plants will show few if any symptoms, while under heavy pressure, the plants may show a moderate level of infection (whereas susceptible BBL types will be 100% molded). Cultivars with this form of resistance would not need any supplemental control with fungicides, whereas under heavy pressure, fungicides might be required, but at a reduced frequency or quantity. The objective of this study was to determine whether OR6771 would benefit from an integrated mold control approach that included fungicides typically used in snap production, Topsin M and Rovral tankmixed. 

White mold pressure was extremely high in this field with as much as 100% of the plants infected with mold in some plots and an average of 61% of plants infected in OR91G and OSU5630 plots. The varieties OSU5630 and OR91G had the greatest white mold ratings, and the application of Topsin+Rovral fungicides reduced white mold incidence in these varieties significantly and increased yield slightly. In contrast to OSU5630 and OR91G, fungicides had no effect on pod yield of OSU6771, number of plants infected, and mold severity ratings, even though plant density and biomass was similar to the other lines. This suggests that indeed the resistance of OSU6771 to white mold should reduce the amount and/or frequency of fungicidal controls needed for production of this variety. However, the full monetary benefit of resistance in OSU6771 was not fully realized in this study because pod yield of OSU6771 was lower than that of OSU5630 and OR91G.