Peanut cultivars with different disease reactions to Sclerotinia blight received a variable number of applications of iprodione at 1.12 kg/ha or fluazinam at 0.56 kg/ha to determine the most efficient management program. Significant (P ≤ 0.05) cultivar x treatment interactions occurred for each fungicide. In two trials with iprodione, two applications reduced disease incidence for the susceptible cultivar Okrun from 62 to 27% as compared to the control, and increased yield from 2034 to 2581 kg/ha. Three applications did not improve disease control or increase yield as compared to two applications. Iprodione did not affect disease incidence or yields of the moderately resistant cultivar Spanco (9%, 2475 kg/ha) or the resistant cultivar Tamspan 90 (3%, 2903 kg/ha). In three other trials, fluazinam reduced disease incidence in one or more trials and increased yields across trials for all cultivars. Two applications provided the best disease control for Okrun as disease incidence was reduced from 77 to 22%. However, the increase in yield for one (1034 kg/ha) and two (1415 kg/ha) applications did not differ. Reductions in disease incidence with fluazinam varied for Spanco and Tamspan 90, and the yield increase was less than for Okrun. Two applications for Spanco reduced disease incidence from 17 to 7% and increased yield from 2900 to 3484 kg/ha. One application to Tamspan 90 reduced disease incidence from 10 to 5% and increased yield from 3348 to 3891 kg/ha. Tamspan 90 had the highest yield in all trials regardless of fungicide treatment.
1 Approved for publication by the director, Oklahoma Agricultural Experiment Station, Stillwater, OK. This study was funded in part by Hatch project H2159 and the Oklahoma Peanut Commission.