Evaluation of Dyfonate for Control of Early-Season Insect Pests on Cotton, 1986

Two small-plot field studies were conducted to evaluate the effectiveness of Dyfonate MS for control of early-season insect pests on dryland cotton. In test 1 (located on a commercial farm near Corpus Christi, TX), three treatments and an untreated were compared in four-row by 50-ft plots of 'GP-3774' cotton planted 7 Mar on 30-inch rows. Treatments in test 1 were applied beginning at the four-leaf stage on 11, 16, 24 and 29 Apr. In test 2 (located at the Texas A&M Research and Extension Center at Corpus Christi), three treatments and an untreated were compared in four-row by 50-ft plots of 'TAMCOT SP-37' cotton planted 22 Mar on 38-inch rows. Treatments in test 2 were applied beginning at the three-leaf stage on 16, 24, 29 Apr, 6 and 13 May. Treatment applications for both tests were made with a C02 pressurized (36 psi) backpack sprayer equipped with size 3-X hollow-cone nozzles. In test 1, applications made on 11, 16, and 24 Apr were directed over the row bed (i.e., one nozzle/row) at 2.8 gal total spray/acre, whereas the application on 29 Apr was broadcasted over the row bed and middles (i.e., 3 nozzles/row) at 8.2 gal total spray/acre. In test 2, directed applications were made on 16 and 24 Apr, and broadcast applications were made on 29 Apr, 6 and 13 May. Efficacy of treatments was evaluated in both tests by inspecting: (1) the terminals of 20 randomly chosen plants in each plot for the presence of fleahopper nymphs and thrips, and (2) the terminal leaves (third leaf from apex) of 10 randomly chosen plants in each plot for the presence of aphids. In each test, seed cotton was hand-harvested twice from a 6.8-ft section of row in each plot for yield analysis.