Efficacy of foliar fungicides for management of Cercospora sojina on soybean in east Mississippi I, 2014

摘要

Foliar fungicides were evaluated on soybean at the North Farm Starkville, Mississippi. The previous crop was soybean. The trial was planted on a Marietta fine sandy loam on 22 May to the soybean variety Armor DK 4744, a frogeye leaf spot susceptible soybean variety. Plots consisted of four rows spaced 38-in apart and 40 ft. in length. Treatments were replicated four times in a randomized complete block design. Plots were not irrigated. Fungicide treatments were applied on 30 Jun (R3) to each plot using a CO2-pressurized, Bowman MudMaster sprayer fitted with TeeJet 110015AIXR nozzles spaced 20 in. apart and delivering 15 gal/A at 40 psi. A non-ionic surfactant (Induce) was added to each treatment at 0.25% v/v. Disease severity ratings were visually assessed based on the presence of disease symptoms from the two center rows of the soybean plant canopy. Plots were rated pre-application (30 Jun), 16 days (16 Jul) and 50 days (19 Aug) post-treatment. Visual assessments of disease were made based on a scale of 0 to 9 where 0 = no disease present and 9 = approximately 90% of the leaf surface covered with lesions. Visual assessments of phytotoxicity present in each plot post-application were made on a scale of 0 to 100% based on the percentage of foliar tissue affected in each plot. Plots were harvested with a plot combine on 16 Oct and yields were adjusted to 13% moisture. Data were subjected to analysis of variance and means were compared at the 0.05 significance level using Fisher's protected least significant difference (LSD) test. Prior to statistical analysis, assessments of phytotoxicity were transformed using a square root transformation. Data presented in the table below were back-transformed to percentages for ease of presentation.