Olfactory basis of cannibalism in grasshoppers (Orthoptera: Acrididae): III. Use of attractants on carbaryl wheat bran bait.

Two known necrogenic attractants, linoleic acid (18:2) and linolenic acid (18:3), were added to carbaryl bran bait to enhance control of rangeland grasshoppers in southeastern Wyoming. The primary goal was to increase control of species of Gomphocerinae, which normally do not consume bran bait. Each attractant was applied at 1, 5, and 10 grasshopper equivalents (GE) (e.g., a 1-GE treatment had the amount of fatty acid per unit weight of wheat bran that would be found in one grasshopper). Controls included carbaryl bran with no attractant and no treatment. Bran was applied at a rate of 1 kg/ha to 1-ha blocks on June 6, 1992, with four replicates per treatment and control. Plots were sampled for grasshoppers and nontarget organisms one day prior to and one, two, and three days after treatment. The addition of linoleic acid (10 GE) resulted in significantly lower total grasshopper densities than carbaryl bran alone. None of the attractants significantly improved control of all Gomphocerinae due to inconsistent effects among species. Relative to carbaryl bait alone, all doses of both fatty acids significantly improved control ofAmphitornus coloradus (Thomas). However, the attractants did not change the level of control ofCordillacris occipitalis orAulocara elliotti, and linolenic acid (5 GE) and linoleic acid (1 GE) resulted in significantly poorer control ofAgeneotettix deorum (Scudder) than carbaryl bait alone. Nontarget arthropods were largely unaffected by the attractants, except for the spiders, which were significantly reduced in all linolenic acid treatments.