Soil amendments for management of Phytophthora root rot in avocado and their impact on the soil microbiome

Phytophthora root rot is a major problem for avocado growers around the world. This review summarises the current control measures and their impact on the soil microbiome. The fungicide phosphite is widely used in the avocado industry, and reports from several countries indicate that Phytophthora cinnamomi is developing resistance. For this reason, alternative control measures have been investigated. Applying organic mulches and soil dressings of calcium or silicon provides a level of control. Biological control through the application of suppressive microbes has been actively investigated over many years, but reports of successful field deployment are rare. This review examines the effects on the soil microbiome of these control measures and assesses the future directions for research.