Evaluation of Folicur sensitivity and its effect on soybean yield in Iowa, Illinois, and North Dakota, 2006

摘要

Three sets of cultivars with differing sensitivities to tebuconazole were tested to determine if tebuconazole phytotoxicity affects soybean yield. In 2005, 670 cultivars were treated with two applications of Folicur 3.6F (tebuconazole; 4 fl oz/A + 0.125% NIS). Fromthis study, nine cultivars were selected, three each from different classifications, “resistant” (no reaction), “intermediate” (moderate reaction), or “sensitive” (severe reaction). Plots were established in five locations: Fargo, ND, Cambridge, IA, Crawfordsville, IA, DeKalb, IL, and Urbana, IL. Three cultivars (one from each classification) were planted at the Fargo location. One set of six cultivars(two from each classification) were planted in Cambridge and DeKalb, and a different set of six cultivars were planted at Crawfordsville and Urbana. At all the locations, plots were arranged in a randomized complete block design with four replications. Folicur 3.6F wasapplied at the same rate as in 2005 to each cultivar at the growth stage R3 only or R3 + R5. Untreated controls were included for comparison. Soybean leaves were rated for phytotoxicity two weeks after each fungicide application. Phytotoxicity ratings were based ona 0-5 scale, where 0= none, 0.5= flecks, 1= a few leaves displaying interveinal chlorosis, 2= 10-20% leaves with interveinal chlorosis, 3= 30-40% leaves affected, 4= 40-60% leaves affected, and 5= 60%+ leaves affected. The middle two rows of each plot were harvested andyield was adjusted to 13% moisture. Data were analyzed using the general linear model (GLM) procedure in SAS and means were compared using Fisher’s protected LSD at P=0.05.