By Gary Kruger, PAg, Irrigation Agrologist
Irrigated dry bean production faces several yield and quality-limiting diseases in Saskatchewan. The greatest threats are white mould, caused by Sclerotinia sclerotiorum, and bacterial blight, which may involve several different bacterial pathogens. These diseases are favoured by humid growing conditions.
During the growing season, sclerotinia white mould suppression can be obtained through the application of a foliar fungicide at early flower with a follow-up sequential treatment after about 10 days. Most fungicides will not provide suppression of bacterial blight, since this disease is not caused by a fungus. Exceptions to this are copper-based fungicides, which have a contact activity and are registered for protection against bacterial blight but not white mould. At least one copper treatment has been the industry norm.
An alternate approach that has shown promise for increasing yields in Nebraska is chemigation, ground or aircraft application of OxiDate® 2.0. The product has two active ingredients, hydrogen peroxide and peroxyacetic acid, and is presently registered for ground application against bacterial blight (Xanthomonas campestris pv.phaseoli) in Western Canada. Research is being conducted at the Irrigation Crop Diversification Corporation (ICDC) to gather information to potentially support a registration against white mould with chemigation. The results of work conducted in North Dakota last year were mixed for ground application, but the hope is that with increased water volumes and foliage contact time through chemigation application, the level of control can be increased. Development work in Nebraska over the last four years has shown promise to increase the effectiveness of control with this approach.
ICDC had also been conducting demonstrations with Contans®, a biological control agent that destroys sclerotia bodies in the soil. This biological control practice requires fall application of the control agent to improve infection of sclerotia bodies with the active organism Coniothyrium minitans. Work in North Dakota suggests that fall application of Contans® WG with a pivot also provides improved control of white mould under irrigated conditions. A maintenance program of applying a low rate of Contans® WG is recommended to maintain higher levels of C. minitans in the soil as a long-term management strategy.