Monitoring methods and spatial patterns of European canker disease in commercial orchards

Abstract

European canker (Neonectria ditissima) kills trees and decreases production in apple orchards. To determine a level of disease control or the extent of its spread in commercial orchards, efficient monitoring methods are required. In this study, we investigated two monitoring methods, sampling a single row and systematic sampling of an orchard block. The spatial pattern of disease within blocks, and whether this changes over time, was also investigated. The accuracy of single-row monitoring depended on the level of canker in the orchard and the patchiness of the distribution of infected trees. However, single-row monitoring tracked changes over time in incidence, severity and type of canker sufficiently well and was efficient. The spatial patterns of disease incidence across the blocks were non-random, but showed hotspots which did not change significantly over time.