Internal biosecurity between islands: identifying risks on pathways to better manage biosecurity threats

The Chatham Islands possess several endemic vertebrate, invertebrate and plant species and are free of many pests found on mainland New Zealand. Keeping out unwanted organisms that may threaten the agricultural sector on the islands is important for the present and future local economy. Research found that soil intercepted from used machinery destined for the Chatham Islands contained a range of plants, insects and nematodes, but the number and diversity of these taxa varied with the type of contamination. Sampling of Chatham Island pasture, indicated an absence of Sitona obsoletus, but the presence of other insect species including porina and Irenimus aequalis that originated from mainland New Zealand. Despite being some 750 km from New Zealand, transport routes allow for the movement of unwanted and invasive invertebrate species to the islands. Identifying dispersal pathways and instigating appropriate management plans compatible with an existing biosecurity programme, will reduce the flow of invertebrate and plant pests.