Evaluation of oomycete-specific fungicides combined with varietal resistance for management of black shank in burley tobacco, 2018

摘要

On 8 Jun, a one-acre field was transplanted with burley tobacco on a commercial grower's farm in Clark County, KY. Previous race-typing established that P. nicotianae races 0 and 1 were present in this field. Land preparation, fertility, weed management, and insect control were managed following University of Kentucky Cooperative Extension Service guidelines. Fungicide tests were performed in varieties 'H-404LC' (rated 0 on a scale of 0-10 for resistance to both races of P. nicotianae, where 10 = highly resistant), 'KT-215LC' (rated 10 and 9 for resistance to races 0 and 1, respectively, of P. nicotianae), and 'TN-90LC' (rated 4 for resistance to both races of P. nicotianae). Tobacco transplants were set in fungicide test plots, composed of approximately 34 plants in two adjacent rows, alternated with nontreated rows of H-404LC or NC-129LC (rated 0 for resistance to both races of P. nicotianae). An approximately 5ft plant-free break separated treated plots within the same rows. Transplants were spaced approximately 21 in. apart within the row with approximately 40 in. between rows. Fungicide by variety treatments are shown in the table and were arranged in the field as a randomized complete block design with four replications, including three nontreated controls (NTCs); one of each variety. Fungicide treatments occurred a maximum of three times during the growing season: as a soil spray (7 Jun; application A) or at transplanting (8 Jun; application B), first cultivation (29 Jun; application C), and/or layby (11 Jul; application D). Application A treatments were broadcast onto soil in the plot area prior to bed formation in approximately 300 gal/A volume. Application B treatments were injected by plot into a grower standard of 200 gal/A transplant water mixture, which included insecticides (Coragen 7.0 oz/A and Wrangler 7.0 oz/A). Two experimental treatments were included at either Application A or B, A22556A and A21723E, from Syngenta Corp. Application C and D treatments were applied as bandedsprays (one band on each side of the row directed to the soil) with a CO2-pressurized backpack sprayer at a rate of 30 gal/A. These treatments were incorporated by tractor cultivation within 3 hr of application. Black shank incidence was determined on 26Jun, 18 Jul, 7 Aug, and 6 Sep by counting live plants per plot. Tobacco was harvested by plot on 7 Sep, assayed for green stick weight on 10 Sep after three days of wilting in the field, and then hung in a commercial curing barn until 19 Dec when it wasassayed for cured yield. Cured leaf per stalk was extrapolated to yield/A based on a plant population of 7,200 plants/A. Final black shank incidence, green stick weight, and cured yield were subjected to analysis of variance (ANOVA) using PROC GLM in SAS 9.4 with means separation by Tukey's post-hoc test (P < 0.05).