Possum (Trichosurus vulpecula) control benefits native beech mistletoes (Loranthaceae)

The Australian brushtail possum (Trichosurus vulpecula) has been blamed for the decline of three native New Zealand beech mistletoe species (Alepis flavida, Peraxilla tetrapetala and Peraxilla colensoi, Loranthaceae), but there are few quantitative data on possum effects, and anecdotal evidence is often conflicting. We present results from two monitoring programmes that suggest possum control operations can improve mistletoe health. In the Eglinton Valley significantly more Alepis flavida plants outside a possum control area declined in condition than Peraxilla spp. inside the control area from 1995 to 1997. In 1997, the control area was extended to include A. flavida plants and their condition significantly improved by 1999. Alepis flavida at Eglinton was also compared to A. flavida at Mavora Lakes, where no control was undertaken. Significantly more of the Eglinton plants declined from 1995 to 1997, while the reverse was true from 1997 to 1999, after the Eglinton site was controlled. In the Hurunui River Valley significantly more mistletoes improved or remained in the same condition within the possum control area than outside the control area between 1997 and 2000. Overall, these results suggest that possum control is an effective tool for protecting native beech mistletoes, but more monitoring data are needed to understand how frequent and how intense control efforts must be to afford this protection.