Field Evaluation of Diflubenzuron and Carbaryl Bran Baits Against Grasshopper (Orthoptera: Acrididae) Populations in South Dakota

Abstract

Control of rangeland grasshoppers with flaky wheat bran treated with diflubenzuron and carbaryl was tested in South Dakota during 1988 and 1989. Diflubenzuron (0.75 or 1.0% [AI]/kg) was delivered at 1.1 and 2.2 kg/ha and carbaryl (2.0% [AI]/kg) at 1.1 kg/ha. In 1988 and 1989, diflubenzuron and carbaryl treatments were equally effective. The 2-yr (1988 + 1989) combined total population reductions ranged from 34.9 ± 10.5% for the diflubenzuron 0.75% (AI)/kg applied at 1.1 kg/ha to 66.7 ± 11.0% for the diflubenzuron 1.0% at 2.2 kg/ha. The standard carbaryl 2.0% AI/kg at 1.1 kg/ha was 57.9 ± 6.0%. The variability between the applications at the two sites was caused mainly by the difference in prevailing weather patterns. Sublethal effects were noted for the effects of treatment on the average age of the grasshoppers. At Edgemont, SD, in 1989, five species of grasshoppers occurred in all before-treatment counts and were analyzed in detail. Two species, Cordillacris occipitalis (Thomas) and Amphitornus coloradus (Thomas), did not feed on the bait and showed no mortality. Aulocara elliotti (Thomas) was controlled, but no significant differences among the treatments were detected. Diflubenzuron and carbaryl treatments significantly reduced populations of Ageneotettix deorum (Scudder) and Phlibostroma quadrimaculatum (Thomas). Observations 1 yr after treatment of these species revealed that P. quadrimaculatum and A. deorum continued to exhibit residual effects of treated bran.