Selected Insecticide/Nematicides for Control of Thrips in Virginia Cotton, 1995
Abstract Efficacy of selected insecti-cide/nematicides was evaluated for control of thrips (primarily F. fusca) in Virginia cotton. ‘Sure-Grow 501’ cotton was planted 1 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, Va. using a 36-inch row spacing. All treatments were applied into the seed furrow (IF) at the time of planting, granules using tractor-mounted inverted jars with lid holes calibrated to deliver exact amounts via gravity; liquids (IF, spray) with a CO2 pressurized tractor-mounted sprayer calibrated to deliver 5.0 gal/acre at 24 psi through one SS8001E flat fan nozzle mounted just above planter disks and turned parallel to the row direction to deliver the spray fan into the seed furrow. Gaucho seed treatment was applied commercially. A RCB design was used with 4 replicates; plots were 4 rows by 30 ft. Adult and immature thrips were counted on 3 dates by cutting and placing 5 plants per plot into jars containing soapy water. Thrips were filtered and counted in the laboratory. Thrips injury to plants was determined by visually rating injury using a 0 to 5 scale, where 0 = no thrips induced plant injury, 1 = 10% injured leaves, no bud injury; 2 = 25% injured leaves, no bud injury; 3 = 75% injured leaves, and 0 to 25% buds injured; 4 = 90% injured leaves, and greater than 25% buds injured; and 5 = dead plants. Flower number was used as a measure of plant maturity as affected by thrips injury. Flowers were counted one time on 19 Jul in 6 row ft per plot. Yield was determined by harvesting the 2 center rows of each plot (60 row ft per plot) using a commercial 2-row John Deere cotton combine. Lint values were calculated as 37% of total plot weights, assuming 63% was seed and trash. Data were analyzed using ANOVA and LSD, or Duncan’s new multiple range statistical procedures.