Control of Keithia thujina Durand by Cycloheximide and Derivatives

Abstract

INFECTION of seedlings and transplants of Western red cedar (Thuja plicata Lamb.) by Keithia thujina Durand frequently causes heavy losses in forest nurseries in Britain. In extensive field control trials carried out over the past ten years, the fungus has displayed a high resistance to a wide range of fungicides. Only copper fungicides showed any effectiveness, but the low level of control did not warrant their general field use. At the present time, Thuja is raised by the Forestry Commission by rotation sowing in a small number of nurseries which are isolated from possible sources of the disease. However, effective chemical control is still highly desirable, as avoidance of the disease by rotation sowing requires several economic forest nursery units which are not available to many private woodland owners.