Evaluation of fungicides for control of white rust on spring-cropped spinach, 2014

摘要

The experiment was conducted at the Entomology and Plant Pathology Research Farm in Stillwater in a field of Easpur loam previously cropped to spinach. Granular fertilizer (75-0-0 lb/A, N-P-K) was incorporated into the soil prior to planting on 12 Marat a seeding rate of two seeds per inch. The herbicide Dual Magnum II Parallel 7.6E at 0.75 pt/A was broadcast post-emergence on 31 Mar. Plots were top-dressed with granular fertilizer (50-0-0 lb/A, N-P-K) on 4 Apr. Plots consisted of 4-row beds, 20-ftlong, with rows spaced 14 in. apart. The experimental design was a randomized complete block with four replications separated by a 5-ft-wide fallow buffer. Fungicides were broadcast using flat-fan nozzles (Tee-jet 8002vk) spaced 18-in. apart with a CO2-pressurized wheelbarrow sprayer. The sprayer was calibrated to deliver 26 gal/A at 40 psi. Treatments were applied on 7-day intervals beginning at the first true-leaf stage. Plots received a total of 12.45 inches of sprinkler irrigation at 0.1 to 1.0 in.water per application as needed to promote crop and disease development. Rainfall during the cropping period (12 Mar to 27 May) totaled 0.84 in. for Mar 0.84 in. for Apr, and 0.65 in. for May. Disease incidence (percentage of leaves with symptoms) and severity (percentage of leaf area with symptoms) were assessed on 27 May. Five, 6-in.-long row segments were harvested arbitrarily from the middle two rows of each plot. The harvested leaves were bulked and mixed, and disease severity was visually estimated on 30 blindly sampled leaves. Data were analyzed using the GLM procedure of SAS 9.3 and means were separated with Fisher's least significant difference test where indicated by a significant (P< 0.05) treatment effect.