Barry Jacobsen, Joyce Eckhoff, Jerry Bergman

Two studies on Cercospora leaf spot were conducted, a fungicide screening trial, and a trial that integrated fungicide, resistant varieties and a predictive model.  The onset of disease was approximately July 12 and disease development thereafter was the lowest in six years.

Cercospora Variety Resistance Trial

Three varieties differing in their KWS (0-9 with 9 being most susceptible and 0 being immune) were examined for their response to varying numbers of fungicide applications. When analyzed across varieties there were no differences in % sucrose or sucrose yield. Low disease intensity (low AUDPC) suggested that except for the susceptible variety Beta 2185 there would be no economic yield effects. Varieties and spray programs differed significantly in AUDPC.  To achieve optimal disease control on Beta 2185 (KWS=6.3) required 3-4 sprays, on the moderately susceptible  HH111 (KWS=5.3) only  two sprays were required and on the highly resistant HM 7054 only one spray was required. Thus, under low disease pressure the choice of a moderately resistant or resistant variety with reduced fungicide application would be more profitable than the susceptible variety with more fungicide applications

Fungicide applications to sugarbeet varieties differing in resistance to Cercospora leaf spot and a comparison to use of the Minnesota prediction model (Program spray)

 First spray applied July 12 (Eminent 13 0z/A); Second spray 7/26 (Benlate 0.5 lb/A);
Third spray 8/09 (Super Tin 5 oz/A); Fourth spray 8/23 (Super Tin 5 oz/A).
ns= not statistically significant.