Fungicide application methods for black shank control in flue cured tobacco in Virginia, 2007

摘要

Experimental plots consisting of 4 test rows, 50 foot long, were established on 46-inch row centers in a naturally infested commercial flue cured tobacco field in Pittsylvania County, Virginia. All data were collected from the 2 center rows of each plot. Plots were arranged in a split-plot experimental design with 6 replications. Main plots consisted of soil fungicide application methods, which involved comparing broadcast sprays with use of a single, narrow-angle (4004) spray tip to apply the product in a 12 inch band or use of a single solid cone (TG1) spray tip to apply the fungicide overtop of plants in sufficient spray volume that the spray solution would “rundown” plant stems to the soil surface surrounding the base of each plant. Subplots consisted of the flue cured cultivars NC 71 and K346, which were mechanically transplanted on 7 May. Fungicide treatments were applied at first cultivation on 22 May (air temperature 77oF, soil temperature 76oF, relative humidity 56%, wind speed 1 mph, average spray volume 31 gal/A) and at layby on 8 Jun (air temperature 87oF, soil temperature 78oF, relative humidity 67%, wind speed 3.6 mph, average spray volume 28 gal/A). Fertilizer, pest control and other cultural practices followed the recommendationsof Virginia Cooperative Extension. Disease was assessed by counting the number of symptomatic, dead, and missing plants approximately every 14 days after transplanting. Final black shank incidence was calculated as the percentage of such plants on eachassessment date relative to the initial stand count on 8 May. Weather during the entire growing season was hot and extremely dry, but the field was not irrigated.