(F125) WHEAT: Triticum aestivum L. EVALUATION OF INSECTICIDES TO CONTROL ARMYWORMS ON WHEAT, 2001 & 2002 Donald R. Johnson University of Arkansas Cooperative Extension Service 2301 South University Avenue Box 391 Little Rock, AR 72203 Tel: 501-671-2000 Fax: 501-671-2303
[email protected] Gus M. Lorenz III Jack D. Reaper III John D. Hopkins T. J. Kring Department of Entomology University of Arkansas AGRI 319 Fayetteville, AR 72701 Tel: 479-575-3186 Fax: 479-575-2452 Armyworm (AW): Pseudaletia unipuncta (Haworth) An infestation of armyworm (AW) in wheat in Lonoke County, AR, was selected as the site of the experiments for 2001 and 2002. The objective of the experiments was to determine the relative effectiveness of various insecticides to control AW in wheat. Insecticides were applied using a two-man boom equipped with a CO 2 backpack sprayer. Plot sizes were 14 ft x 50 ft with treatments in all three tests arranged in a RCB with four replications. Observations were made 2 and 5 DAT in 2001 and 2.5 and 3.5 DAT in 2002. Live AW larvae were counted in 1-ft2 grids at three (2001) and two (2002) randomly selected locations within each plot. At harvest maturity, a plot combine was used to harvest 50-100 ft2 from each plot to determine yield. ANOVA was performed and DNMRT (P = 0.05) was used to separate means only when AOV Treatment P(F) was significant at the 5% level. In test 1, 2 DAT, all insecticide treatments resulted in significantly fewer AW larvae than the control (Table 1). At 5 DAT, the low rate of Tracer was not significantly different from the untreated check but obtained higher control than other insecticide treatments. In test 2, at 2 DAT, significant differences were observed between treatments (Table 2). Steward (0.065 and 0.09 lb (AI)/acre rates) resulted in significantly better control than the Confirm and Intrepid treatments; however, no differences were observed with Steward (0.04 lb(AI)/acre) and the other treatments. By 5 DAT, all treatments had fewer live larvae present than the untreated check. All three rates of Steward had significantly less larvae than the standard treatment of Tracer. No difference was observed between Steward and the other treatments. It is important to mention the increased control seen with Confirm and Intrepid at 5 DAT. These products cause mortality slower than others, as they have activity on the molting process. The live larvae seen at 2 DAT more than likely ceased feeding shortly after the insecticide application. Three days later, they were obviously dead, and the control
of these products was comparable to the others. In test 3 conducted in 2002, Mustang Max (0.02 lb(AI)/acre), Warrior T (0.025 & 0.03 lb(AI)/acre) and XDE-225 (0.0125 lb(AI)/acre) had significantly lower counts than other treatments (Table 3). At 3.5 DAT, all insecticide treatments with the exception of Tracer had counts signicantly lower counts than the untreated check.
