F39

Abstract

Selected insecticides applied as a liquid into the seed furrow at planting and foliar treatments were evaluated for control of thrips in cotton. ‘PHY 499 WRF’ cotton was planted 2 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using 36inch row spacing. Liquid in-furrow (IF) Admire Pro and Verimark treatments were applied into the seed furrow at 5 gpa using a microtube mounted between the disc openers, pressurized by CO2 at 51 psi. Foliar Benevia and Orthene treatments were broadcast at first true leaf stage (BC @ 1 tl) on 20 May with a CO2-pressurized backpack sprayer at 14.3 gpa and 16.8 psi through 8002VS nozzles spaced 18 inches apart on the spray boom. A RCBD was used with 4 replicates; plots were 4 rows by 35 ft. 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. Thrips counts were taken from selected treatments on four dates by collecting five plants per plot in Mason jars containing approximately 500 ml soapy water. Thrips were counted under a stereoscope following suction filtration. Yield was determined by harvesting 2 rows of each plot (70 row ft) using a commercial 2-row cotton picker. Sub-samples were ginned to determine lint versus seed and trash weight (42.1% lint, 57.9% seed and trash). Data were analyzed using ANOVA and LSD statistical procedures.