Comparison of single and multiple applications of an insecticidal bait forcontrolling grasshoppers (Orthoptera : Acrididae) on mixed-grass prairie

A field study was conducted to determine if high dosages and multiple appli cations of insecticidal baits could be used to increase mortality of rangel and grasshoppers. Twenty-four rangeland plots in western North Dakota were treated with either single applications of 2% (AI) carbaryl bran bait at 1. 68, 3.36, or 5.04 kg/ha; double applications of carbaryl bran bait at 1.68 kg/ha for each application; triple applications of the bait at 1.68 kg/ha; or left untreated. Densities of all grasshopper species were estimated befo re treatments and 2, 4, and 7 days after treatments. The insecticidal bait treatments caused significant reductions (57-100%) in densities of Aulocara elliotti Thomas, Melanoplus sanguinipes (E), Camnula pellucida Scudder, an d Ageneotettix deorum (Scudder), but had no significant effect on Aeropedel lus clavatus (Thomas) or Melanoplus bivittatus (Say). A single application of the insecticidal bait at 5.04 kg/ha caused significantly greater mortali ty of A. elliotti (82%) than single applications of the other dosages. Dosa ge had no consistent effect on densities of M. sanguinipes, C. pellucida, A . deorum, or all species combined, after 2 days. Multiple applications of t he insecticidal baits caused additional 32-52% reductions in densities of t otal grasshoppers after each successive application, indicating that the qu antity of bait can affect grasshopper mortality. However, final mortality o f total grasshoppers after 7 days was not affected by high dosages or multi ple applications of the insecticidal baits, indicating that multiple and hi gh dosages of insecticidal baits had no real advantage over single applicat ions at 1.68 kg/ha.