Impact of recommended fungicide programs on leaf spot and stem rot control in Southeast Alabama, 2014

摘要

The study area at the Wiregrass Research and Extension Center, which is maintained in a peanut-corn rotation, was turned with a moldboard plow and worked to seed bed condition with a disk harrow. On 20 Apr, rows were formed with a KMC strip till rig with rolling baskets. On 16 May, the peanut cultivars Georgia-06G and Tifguard were planted at a rate of 6 seed/ft in a Dothan fine sandy loam (OM<1%) soil. Thimet 20G at 5 lb/A was applied in-furrow for thrips control. Weed control was obtained with a 24Apr pre-plant, incorporated broadcast application of 1 qt/A Sonalan HFP + 1.5 pt/A Dual Magnum II followed by a broadcast applications of 3 oz/A Valor on 20 May and 4 oz/A Cadre on 17 Jun. Soil fertility recommendations of the Alabama Cooperative Extension System were followed. The test area received 0.5 in. of water on 7 Jul followed by 1.0 in. of water on 31 Jul, 8 Aug, 19 Aug, 4 Sep, and 17 Sep. A split plot design was used with peanut cultivar as whole plots and fungicide treatments as sub-plots. Whole plots were randomized in four complete blocks. Subplots consisted of four 30-ft rows spaced 3-ft apart that were randomized within each whole plot. Fungicides were applied on 1 = 1 Jul, 1.5 = 8 Jul, 2 = 14 Jul, 3 = 29 Jul, 4 = 11 Aug, 5 = 26 Aug, 6= 12 Sep, and 7 = 26 Sep with a tractor mounted boom sprayer with three TX-8 nozzles per row calibrated to deliver 15 gal/A of spray volume at 45 psi. On 13 Oct, early and late leaf spot diseases were rated together using the 1-10 Florida peanut leaf spot scoring system where 1 = no disease, 2 = very few leaf spots, 3 = few leaf spots in lower and upper canopy, 4 = some leaf spotting and < 10% defoliation, 5 = leaf spots noticeable and < 25% defoliation, 6 = leaf spots numerous and < 50% defoliation, 7= leaf spots very numerous and < 75% defoliation, 8 = numerous leaf spots on few remaining leaves and <90% defoliation, 9 = very few remaining leaves covered with leaf spots and < 95% defoliation, and 10 = plants defoliated or dead. On 21 Oct, stem rot loci counts (1 locus was defined as < 1 ft of consecutive stem rot-damaged plants per row) were made immediately after plot inversion. Plots were combined several days after inversion. Yields were reported at 6.6% moisture. Significance of interactions was evaluated using PROC GLIMMIX in SAS. Statistical analyses were calculated on rank transformations for non-normal data for leaf spot diseases and stem. Non-transformed data are reported. Means were separated using Fisher's least significant difference (LSD) test (P<0.05).