A Review of Neofabraea malicorticis Biology and Management of Anthracnose Canker in Apple Orchards in the Maritime Pacific Northwest

摘要

Cider apple (Malus xdomestica Borkh.) is an emerging crop in western Washington and the maritime Pacific Northwest (PNW) region in general, but the planting of new orchards and orchard productivity are limited by the widespread occurrence of anthracnose canker, caused by the fungal pathogen Neofabraea malicorticis (H.S. Jacks). In the maritime PNW region, the pathogen induces tree cankers that can kill newly planted trees and structurally weaken established trees. Current management practices include excising cankers during the dormant season and applying fungicides prior to autumn rains. Yet these management practices have not provided adequate disease control in the region, as new N. malicorticis infections of susceptible hosts occur even after applying the recommended controls. Poor management of anthracnose canker in the region is likely due to the lack of effective treatments, treatments being applied at the wrong time, or treatments not being applied over an adequate period of time. High inoculum levels and favorable environmental conditions for pathogen infection in the region also contribute to disease severity. Research on disease development and the management of N. malicorticis in an orchard environment is limited to dessert apples and is contradicting, which further exacerbates the difficulty in developing an effective disease management plan for cider apples. If cider apple production is to be successful in the maritime PNW, it is necessary to have a more comprehensive understanding of the pathogen, and to incorporate this knowledge into the development of an effective plan to manage anthracnose canker on apple. The objective of this review is to provide an overview of the existing literature on Neofabraea spp. in apple orchards, address factors that may explain why managing anthracnose canker has been difficult, and to identify topics for future research that will lead to more effective disease management.