This technique is unlikely to provide the type of control achieved with herbicides. Rather, the aim is to reduce the growth rate, seed production and density of gorse. The gorse spider mite is now well established throughout most of New Zealand. The tiny red mites live in colonies and spin webbing over the gorse. During summer, females lay clusters of eggs on the gorse stem.
Mites are very susceptible to environmental conditions, particularly temperature and rainfall.
At higher temperatures, mites will breed and develop faster. The original strain of gorse spider mite which came from England did not do well in some areas. Five new strains have since been imported from Spain and Portugal. Although the different strains of gorse mites look alike, their responses to environmental conditions are different, which affects the success of populations in different climates. The new strains are expected to perform better in warmer, wetter climates than the original strain.