Reaction of shrub-type roses to three foliar diseases in North Alabama, 2009.

摘要

Roses were planted in Dec 06 and Jan 07 in a Hartsell/Wynville soil at the Sand Mountain Research and Extension Center in Northeast Alabama (USDA Plant Hardiness Zone 7a). A drip irrigation system was installed after planting and the plants were watered as needed. Pre-emergent weed control was provided by an application of a tank mixture of Surflan AS at 2 qt/A and Gallery at 1.33 lb/A on 11 May. On 5 Jun 09, Select at 8 fl oz/A plus 1% v/v of Agridex surfactant was applied for post-emergent bermudagrass control. Escape weeds were pulled by hand. On 16 Apr, approximately 1 cup of 16-4-8 analysis fertilizer was evenly distributed around the base of each plant. An application of 0.5 cup of 15-5-10 analysis fertilizer per plant was made on 9 Jul and 17Aug. Bravo Weather Stik 6F (chlorothalonil) at 1 qt/A was applied at approximately 2-wk intervals from 28 Apr to 14 Aug with a CO2pressurized sprayer. The experimental design was a randomized complete block with five two-plant replicates. Black spot andCercospora leaf spot severity were 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 17 Apr, 27 May, 23 Jun, 24 Jul, and 4 Sep. Data from the 13 Aug rating is displayed in the table. Powdery mildew was assessed on 26 May using the Horsfall and Barratt rating scale where 0 = no disease, 1 = 0 to 3%, 2 = 3 to 6%, 3 = 6 to 12%, 4 = 12 to 25%, 5 = 25 to 50%, 6 = 50 to 75%, 7 = 75 to 87%, 8 = 87 to 94%, 9 = 94 to 97%, 10 = 97 to 100 %, and 11 = 100% of leaves colonized. Significance of treatment effects were tested by analysis of variance and Fisher’s protected least significant difference (LDS) test (P<=0.05).