Riverland citrus growers, CSIRO entomologists and the Bookmark Biosphere Reserve are working together to reduce on-farm costs by better managing soil biological diversity. Properties with high soil biodiversity were found to have many kinds of pests, but none causing significant crop damage. Properties with low soil biodiversity often had at least one major pest species. It emerged that perennial groundcover provides superior habitat, and a supplementary pollen food source, for predatory mites that feed on the larvae of Kelly's citrus thrips, a major pest in the region. A diverse groundcover also improves soil water retention, reduces evaporation and increases organic matter. This in turn improved nutrient retention and reduced nutrient runoff to the Murray River.