TOMATO SPOTTED WILT VIRUS SUPRESSION IN TOBACCO WITH UNREGISTERED MATERIALS, 2012

Seven experimental insecticides and two registered insecticides were compared to assess their efficacy in reducing tomato spotted wilt virus (TSWV) incidence in tobacco by reducing feeding by tobacco thrips, the primary vector in this system. Plots consisting of 4 rows of ca. 25 plants per row (0.018 acres each) were established at the Lower Coastal Plain Research Station near Kinston, NC, and the nine insecticide treatments plus an untreated control (UTC) were replicated four times and arranged in a RCB design. Pre-transplant tray drench treatments (PTTD) were applied to greenhouse grown plants 16 April in 1 L water using a CO2 pressurized sprayer with a single flat-fan nozzle. Twice the application volume was used to wash the material into the root zone immediately following treatment. Float trays of treated plants were held in separate beds following treatment to prevent cross contamination. Subsequently, the plants were transplanted on April 18, and posttransplant treatments (PTA) were applied with a CO2 pressurized backpack sprayer fitted with a single TG3 solid cone nozzle at 65 psi pressure on 2 May, timed to the third generation tobacco thrips flight. To assess phytotoxicity, the width of the largest leaf on ten plants in rows two and three was measured at three and four weeks after transplant, and the plant height from base to bud was measured on ten plants in these rows at five weeks after transplant. To compensate for uneven fertilizer distribution by the tractor hopper, phytotoxicity data from only the row with widest leaves and tallest plants were analyzed for each plot. Thrips were counted on ten plants in the middle row (row 2 or 3) with the tallest plants 24 days after pre-plant treatments (10 days after post-transplant treatment) and on five plants in the middle row with the tallest plants 37 days after pre-plant treatment (23 days after post-transplant treatment). TSWV incidence plant stand counts were recorded weekly in all rows, starting three weeks after transplant and ending nine weeks after transplant. Data were analyzed via ANOVA in (SAS v.9.1.3) and means separations were generated by Fisher’s Protected LSD (α = 0.05).