HYMEXAZOL TREATMENT OF SUGAR-BEET SEED TO CONTROL SEEDLING DISEASE CAUSED BY PYTHIUM SPP AND APHANOMYCES-COCHLIOIDES

Glasshouse and field experiments in 1987-1988 tested the effects of treatment of sugar-beet seed with hymexazol on seedling disease caused by soil-borne Pythium spp. and Aphanomyces cochlioides. In the absence of hymexazol, steeping seed in EMP or thiram had no apparent effect on disease. Incorporating hymexazol in the seed pellet generally increased the number of seedlings established or slightly reduced postemergence losses caused by Pythium spp. in a moderately infested soil. In glasshouse experiments, and in some field experiments, hymexazol reduced the incidence of disease caused by A. cochlioides in proportion to the amount of fungicide applied; rates of application ≥21 g kg-1 seed, which can slow seedling emergence, were necessary for maximum disease control. In other experiments hymexazol had little or no effect on this disease in the field. Treating seed with hymexazol at 10.5-14g kg-1 seed, however, should provide useful protection from these seedling pathogens under moderate disease pressure without risk of phytotoxic effects. © 1990.