Persistence of sodium monofluoroacetate (1080), pindone, cholecalciferol, and brodifacoum in possum baits under simulated rainfall

Abstract

Possums are responsible for major damage to native forests in New Zealand and several baits are available to control this pest. However, there are no data on the persistence of the toxicants in these baits during periods of rain. Four commonly used possum cereal baits were exposed to simulated rainfall to investigate weathering of bait, persistence of toxicant in the bait, and the rate of leaching and persistence of toxicant in the soil. The water‐soluble toxicant 1080 was rapidly leached from bait into soil. Leaching began after only 20 mm of rainfall. Soil concentrations under baits reached a maximum concentration in soil after 100 mm rainfall and declined to near the limit of detection after 250 mm. Pindone concentration in baits declined by 23% after 400 mm of rainfall, but no pindone was found in the soil. Cholecalciferol and brodifacoum concentrations in bait did not decline at all, but trace amounts of cholecalciferol were found in soil under baits. These results demonstrate that if baits containing hydrophobic toxicants, such as brodifacoum, are hand‐laid or spilt from bait stations, they will remain hazardous to livestock and non‐target species, even after exposure to substantial amounts of rainfall.

Keywords:

• toxicant persistence
• bait leaching
• pest management