Evaluation of fungicides for control of watermelon anthracnose, 2009.

摘要

The experiment was conducted at the Oklahoma State University Entomology/Plant Pathology Research Farm in Stillwater in a field of Norge loam previous cropped to mustard greens. Plots were was direct-seeded on 16 Jun. The herbicides Curbit 3E at 3.5 pt/A and Sandia 75DF at 0.75 oz/A were broadcast after planting to control weeds. Plots were top-dressed with granular fertilizer (46-0-0 lb/A N-P-K) on 13 July. Plots were single, 20-ft-long rows spaced 15 ft apart. Plots were thinned to a 2-ft within row spacing. Squash bugs were controlled by spraying Ambush 2E at 12.6 fl oz/A on 1 Sep and 18 Sep. Treatments were arranged in a randomized complete block design with four replications and a 10-ft fallow buffer separating replications. Fungicides were broadcast using a boom with five flat-fan nozzles (8002vk) spaced 18 inches apart that was mounted to a CO2-pressurized wheelbarrow sprayer. The sprayer was calibrated to deliver 24 gal/A at 40 psi. Fungicides were applied on 12 Aug, 24 Aug, and 31 Aug. Plots were inoculated with Colletotrichum obiculare on 12 Aug by spreading 50 ml of colonized oat kernels along the center of each plot. Rainfall during the cropping period (16 June to 30 Sep) totaled 0.61 inches for June, 4.96 inches for July, 7.5 inches for Aug, and 3.07 inches for Sep. Plots received 17 applications of sprinkler irrigation that totaled 4.6 inches of water. Disease incidence was periodically assessed by visually estimating disease incidence (percentage of leaves with symptoms that included defoliation) and defoliation (percentage of leaves defoliated) in three areas of each plot. Yield of marketable melons weighing 12 or more lb was taken on 4 Sep. Melons were classified as diseased or healthy based on the presence or absence of anthracnose lesions.