Evaluation of fungicides for control of powdery mildew on pumpkin, 2014

摘要

The experiment was conducted at the Entomology/Plant Pathology Research Farm in Stillwater, OK in a field of Easpur loam previously cropped to watermelon. The field was direct seeded on 14 Jul. The herbicides Sonalan 3E at 3.5 pt/A, Permit 75DF at 0.75 oz/A, and Round-Up 4L were broadcast after planting to control weeds. Plots were top-dressed with granular fertilizer (50-0-0 lb/A N-P-K) on 5 Aug. Plots were single, 25-ft-long rows spaced 15 ft apart. Plots were thinned to a 2-ft within row spacing.Insects were controlled with Warrior 1F at 3.84 fl oz/A on 5 Sep and 3 Oct. Treatments were arranged in a randomized complete block design with four replications and a 10-ft fallow buffer separating replications. Fungicides were broadcast through flat-fan nozzles (8002vk) spaced 18-in. apart using a CO2-pressurized wheelbarrow sprayer. The sprayer was calibrated to deliver 25 gal/A at 40 psi. Applications were made on ca. 14-d intervals beginning at early fruit set on 5 Sep. Rainfall during the croppingperiod (14 Jul to 6 Nov) totaled 3.38 in. for Jul, 2.01 in. for Aug, 4.19 in. for Sep, 2.18 in. for Oct, and 1.88 in for Nov. Plots received 14 applications of sprinkler irrigation that totaled 6.1 in. of water. Disease incidence was assessed by visually estimating disease incidence (percentage of leaves with symptoms of powdery mildew that included defoliation) and defoliation (percentage of leaves defoliated) in three areas of each plot. Yield of marketable pumpkins was taken on 6 Nov. Data were analyzed using the GLM procedure of SAS 9.3 and means were separated by Fisher's Least significant difference test where indicated by a significant (P<0.05) treatment effect.