Disease resistance of shrub roses in a simulated landscape planting, 2009.

摘要

On 14 Feb 08, bare-root roses were transplanted into raised beds in a Benndale (A) sandy loam soil on 8 ft centers with 13 ft between rows. After each rose was pruned, fresh aged pine bark was distributed on 18 Feb 09. An application of 2.8 oz per plant of 13-13-13 analysis fertilizer on 1 Apr was followed applications of 1.8 and 2.2 oz of a 16-4-8 analysis fertilizer per plant on 16 Jul and 7 Aug, respectively. Pre-emergent weed control was obtained with 13 Feb applications of 2 qt/A of Surflan + 1.0 lb/A of Gallery. The experimental design was a randomized complete block with five three-plant replicates. The study consisted of a split plot design of five replications with rose selections as the main plot and fungicide treatment as the split-plot.Daconil Weather Stik 6F at 2 qt/A was applied at 2- or 4-wk intervals to one plant in each plot. The remaining plant in each plot was left untreated. Fungicides were applied with a hand wand with a TX-8 nozzle to run-off using a tractor-mounted sprayer from 16 Apr to 8 Oct. Black spot and Cercospora leaf spot severity was visually rated using a modified 1 to 10 Florida peanut leaf spot rating scale where 1 = no disease, 2 = very few lesions in canopy, 3 = few lesions noticed in lower and upper canopy, 4= some leaf spotting and <= 10% defoliation, 5 = lesions noticeable and <= 25% defoliation, 6 = lesions numerous and <= 50% defoliation, 7 = lesions very numerous and <= 75% defoliation, 8 = numerous lesions on few remaining leaves and <=90% defoliation, 9 = very few remaining leaves covered with lesions and <= 95% defoliation, and 10 = plants defoliated on 16 Apr, 13 May, 9 Jun, 8 Jul, 14 Aug, and 4 Sep. Significance of treatment effects were tested by analysis of variance and the least significant difference (LSD) test (P<=0.05).