Control of Phytophthora canker with phosphonate in artificially inoculated almond and cherry trees

Abstract

Phosphonate (H3P03; as FOLI-R-FOS 200) applied as either a soil drench, foliar spray or trunk injection before infection inhibited the development of cankers in almond and cherry trees inoculated with Phytophthora cambivora. Phosphonate applied to the foliage in autumn and spring at rates up to 2 g a.i./L was the most effective treatment. Soil drenches up to 10 g a.i./L were also effective, particularly on young trees. Trunk injections completely inhibited the development of P. cambivora in many cases, but due to a possible phytotoxic reaction, the treatment was most suited for mature trees. Foliar sprays of phosphonate are likely to be most practical treatment as these could be applied with other foliar treatments. The inhibitory effect of phosphonate on canker growth persisted for at least 48 weeks after treatment, irrespective of the method of application.