Encapsulated sodium nitrite as a new toxicant for possum control in New Zealand

Sodium nitrite (NaNO2), a commonly used food preservative, has been researched in New Zealand for the control of brushtail possums (Trichosurus vulpecula). In sufficiently high doses, NaNO2 is toxic because it disrupts circulatory transport of oxygen. As NaNO2 is very bitter, encapsulation and mixing it through a highly palatable bait formulation is necessary to effectively deliver it to target pest species. In no-choice cage trials, 12/12 possums consumed a lethal dose of toxic paste bait and died on average after 95.6 minutes (±4.9 SE). In two-choice cage trials 7/8 possums consumed a lethal dose of toxic paste bait and died on average after 96.7 minutes (±11.4 SE). Two field trials targeting possums using this toxic paste in bait stations reduced their abundance by 81.2% (± 2.5% SE) and 72.7% (± 1.6% SE) respectively. NaNO2 paste, known as BaitRite, has been registered in New Zealand as a vertebrate toxic agent for controlling possums.