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Open Access Publications from the University of California

Efficacy data for registration of strychnine grain baits to control pocket gophers (Thomomys spp.)

  • Author(s): Evans, James
  • Matschke, George H.
  • Campbell, Dan L.
  • Hegdal, Paul L.
  • Engeman, Richard M.
  • et al.

Laboratory tests, field telemetry trials, and actual use field efficacy evaluations showed that a 0.5% strychnine alkaloid steam-rolled oat-groat hand-bait formulation (EPA Reg. No. 56228-20) with molasses, salt, glycerine, and soda was effective in controlling northern pocket gophers (Thomomys talpoides). Baits retaining at least 0.5% strychnine (w/w) were as effective (>95% control) as baits with 0.75% and 1.0% strychnine in field telemetry hand-baiting trials as well as operational hand-baiting and burrow-builder baiting field tests in forest habitat. Data indicated that the 0.5% strychnine hand bait (molasses formulation) should be reregistered and would be a good substitute for the 0.5% strychnine-Rhoplex bait (EPA Reg. No. 5622812) currently registered for burrow builder use for pocket gopher control. Both the retention of strychnine on bait and use of a highly palatable top quality bait carrier were two important factors affecting efficacy of the bait.

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