Novel and current rodenticides for pocket gopher Thomomys spp. management in vineyards: what works?

BACKGROUND: Rodenticides are often included as part of an integrated pest management approach for managing pocket gophers (Thomomys spp.) given that they are relatively quick and inexpensive to apply. Strychnine has historically been the most effective toxicant for pocket gophers, but its use is currently limited in the United States; alternative registered toxicants have not proven effective. Recent research with baits containing cholecalciferol plus anticoagulant toxicants proved effective against pocket gophers in a lab setting. Therefore, we established a field study to compare cholecalciferol plus anticoagulant combinations [0.03% cholecalciferol plus 0.005% diphacinone (C + D), 0.015% cholecalciferol plus 0.0025% brodifacoum (C + B1), 0.03% cholecalciferol plus 0.0025% brodifacoum (C + B2)] with strychnine (0.5%) for pocket gopher management.

RESULTS: Strychnine treatments resulted in 100% efficacy after two treatment periods. Both C + D and C + B2 resulted in efficacy significantly greater than 70% after two treatment periods (83 and 75% respectively). Efficacy from C + B1 (85%) was not significantly greater than 70%, but did yield high overall efficacy as well.

CONCLUSION: Although strychnine remains the most effective rodenticide for pocket gopher control, the cholecalciferol plus anticoagulant baits tested would be a good alternative when strychnine is unavailable. C + D may be the best option given that it uses a first-generation anticoagulant as the synergist. © 2016 Society of Chemical Industry.