Management of Cercospora leaf spot in sugar beet and aerobiology of Cercospora beticola Sacc.

Abstract

Cercospora leaf spot, caused by Cercospora beticola Sacc., is the most detrimental disease of sugar beet (Beta vulgaris L.) in the Great Lakes Region. Field trials determined efficacy of BEETcast™ 50/35, BEETcast™ 55/50, and calendar spray schedules using 115 or 235 L ha 1 carrier volume with disease severity value (DSV) accumulation beginning at 1 May or crop emergence. Disease progress was minimized by spray schedules with conservative application intervals compared to longer application intervals. Area under the disease progress curve was reduced by a carrier volume of 235 L ha 1 compared to 115 L ha 1 at one of five sites, and DSV start date at emergence compared to 1 May at one of two sites. Aerial C. beticola conidia concentration was assessed in 6 h intervals and peaked in September with daily mean maxima from noon to 6 pm. Daily mean air temperature was related to daily mean conidia concentration when all data were considered and when concentration exceeded 30 spores m 3.