OLFACTORY BASIS OF CANNIBALISM IN GRASSHOPPERS (ORTHOPTERA, ACRIDIDAE) .3. USE OF ATTRACTANTS ON CARBARYL WHEAT BRAN BAIT

Two known necrogenic attractants, linoleic acid (18:2) and linolenic a cid (18:3), were added to carbaryl bran bait to enhance control of ran geland grasshoppers in southeastern Wyoming. The primary goal was to i ncrease control of species of Gomphocerinae, which normally do not con sume bran bait. Each attractant was applied at 1, 5, and 10 grasshoppe r equivalents (GE) (e.g., a 1-GE treatment had the amount of fatty aci d 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 I-ha blocks on June 6, 1992 , with four replicates per treatment and control. Plots were sampled f or 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 carb aryl bran alone. None of the attractants significantly improved contro l of all Gomphocerinae due to inconsistent effects among species. Rela tive to carbaryl bait alone, all doses of both fatty acids significant ly improved control of Amphitornus coloradus (Thomas). However, the at tractants did not change the level of control of Cordillacris occipita lis or Aulocara elliotti, and linolenic acid (5 GE) and linoleic acid (1 GE) resulted in significantly poorer control of Ageneotettix deorum (Scudder) than carbaryl bait alone. Nontarget arthropods were largely unaffected by the attractants, except for the spiders, which were sig nificantly reduced in all linolenic acid treatments.