Plant Disease Management Handbook

Note These plants do not have a lot of problems and only a few samples have ever come into the OSU Plant Clinic. Cold winter temperatures well below freezing can cause minor bronzing to browning of leaves or serious defoliation depending on the weather conditions. Leaf browning can also occur to plants in full sun. Time of symptom development will help identify the cause. In some situations, plants in poorly drained areas may develop root rot.

Cause Perreniporia subacida, a fungus, causes yellow root rot of several conifer species in Oregon and Washington. It is usually found on suppressed or weakened trees. It is rarely seen in vigorous trees. Hosts other than western red cedar include Douglas-fir, western hemlock, mountain hemlock, lodgepole pine, larch, and grand fir. Most infection results from contact by colonized roots with susceptible roots. Tree roots that are severely stressed appear to be most susceptible to infection and decay.

Cause Fusarium oxysporum f. sp. conglutinans) causes yellows of cabbage and other members of Brassicaceae. This fungus survives in soil as durable resting structures known as chlamydospores which can survive years between hosts. This pathogen can be spread through soil movement on equipment, tools, and footwear as well as infested soil being windborne or waterborne.



By C. M. Ocamb

Cause 'Blackberry Collapse' has appeared in commercial 'Columbia Star' and 'Black Diamond' fields in the Willamette Valley of Oregon. Other names for this disease may include "Cane wilt and canker". The fungi Gnomoniopsis idaeicola, Kalmusia coniothyrium (the cane blight pathogen) and Botrytis sp. have been associated with these collapsed plants and can cause cane lesions. Necrosis was largest on canes inoculated with G. idaeicola.

Note There have been very few beech samples sent into the OSU Plant Clinic. One nursery sample had a Phoma leaf spot diagnosis and there was a diagnosis of Phytophthora and another of Phomopsis. Mature trees in the landscape have been noted to decline in droughty or low soil moisture conditions. Overall, beech diseases are not an important issue in the PNW.