Efficacy of Selected Pyrethroids Against Bollworms Under a Traditional and Extended Spray Interval Spray Approach in Southern North Carolina, 1991

Cotton was planted on 7 May in a Norfolk sandy loam soil near Laurinburg, NC. Recommended agronomic practices for fertility and weed control were followed and 0.67 lb (AI)/acre Temik 15 G was used at planting for thrips. A randomized complete block design with 4 replicates and 6-row (40 inch centers) x 44 ft plots with 8 ft alleys were utilized. Treatments were applied with a backpack CO2-pressurized sprayer calibrated to deliver 8.0 gal water at 50 psi with one TX-8 Spraying Systems® nozzle per row. Applications were made on 15 and 20 Jul and 13 Aug for the conventional (industry recommended rates) and on 15 and 29 July and 13 Aug for the extended interval (1.6 X rates) treatments. The initial application was made at the egg threshold of 10 eggs per 100 terminals. Twenty-five squares and/or bolls were examined per plot (100 total per treatment) for BW and their damage on 25 Jul, 3 and 13 Aug and 19 Sep. Cotton was harvested from the middle 2 rows with a one row John Deere mechanical harvester.