FLEA BEETLE AND BLACK SHANK MANAGEMENT ON FLUE-CURED TOBACCO WITH ADMIRE AND RIDOMIL, 2005

This trial was conducted in a field naturally infested with the black shank (BS) pathogen at the Virginia Tech Southern Piedmont AREC, Blackstone, VA to evaluate the impact of Admire and Ridomil Gold on TFB and BS on flue-cured tobacco. Five treatments, Ridomil Gold alone, two rates of Admire alone and in combination with Ridomil Gold, and an untreated check were established in a RCB design with four replications. Tray drench (TD) applications of Admire were applied with a CO2-pressurized backpack sprayer fitted with an 8003 tip and operated at 30 psi to deliver 13.5 fl oz of water/288-plant float tray on 3 May. An additional 8 fl oz of water per tray was used to rinse the residue off the plants and into the media. On 4 May, 'NC 297', a BS susceptible cultivar, was transplanted into experimental plots, 12 × 30 ft (3 rows × 17 plants). Plots were separated by untreated guard rows and 5-ft fallow strips separated the blocks. On 19 May, Ridomil Gold was applied as a broadcast treatment with a CO2-powered backpack sprayer that delivered 20 gpa at 30 psi through XR8002 nozzles spaced 20 inches apart. The Ridomil Gold was incorporated by cultivation. Weather conditions and soil moisture were good for transplanting and when the Ridomil Gold was applied. Rainfall totaled 2.53, 2.11, 4.65, and 2.96 inches for May, Jun, Jul, and Aug, respectively. Recommended production practices were followed for fertilization, nematode and weed control, and topping and sucker control. TFB feeding holes for the most damaged leaf and TFB were counted on 10 plants per plot every 6 to 8 d from 11 May to 6 Jul. To compare the number of adult TFB emerging from the tobacco root systems, emergence cages set over the cut stems and root systems and sealed with loose soil for 2 randomly selected plants in the third row of each plot. Emerging TFB were collected from the cages every 6 to 8 d from mid-Jun to late Jul. Cages were transferred to new plants every 14 d. From 30 Jun to 12 Sep, dead, missing, and wilted plants with symptoms of BS infection were counted in the first two rows of each plot once every 13 to 20 d. Total symptomatic plants were determined by combining the missing, dead, and wilted plants from each plot for data analysis. Useable leaves on the first two rows in each plot were harvested and the green leaves were weighed on 12 Sep. Data were analyzed by ANOVA and significantly different means were designated by LSD (P ≤ 0.05). Count data for TFB and TFB feeding holes were transformed to Log10(x+1) before analysis. Green leaf yield was transformed to the square root (x + 0.5). Actual means are presented in the tables.