Fungicides and insecticides applied to pelleted sugar-beet seeds — II. Control of pathogenic fungi in soil

Abstract

Hymexazol added to pelleted sugar-beet seed was tested for protection against soil fungi, particularly Aphanomyces cochlioides. The actual concentration in the pellets was checked before sowing and was often considerably lower than the target rate, because hymexazol proved to be rather unstable and could be degraded in the pellet. A good dose-response reaction could be measured at actual rates of hymexazol lower than 20 g active ingredient per 100 000 seeds (g a.i./unit). At rates above 20 g a.i./unit the control of Aphanomyces cochlioides was nearly complete, while an actual concentration of 10 g a.i./unit gave sufficient protection under moderate disease pressure. However under very severe infection pressure even 30 g a.i./unit could not prevent significant plant loss. Different pelleting processes with the same target rate (30 g a.i./unit) showed differences in protective action, but these results were not related to actual amount of active ingredient in the pelleted seed.