Pathology

The core variable to be measured is the presence and incidence of Ophiostomoid fungi in root samples.  An initial survey of all treatment areas was conducted in order to mark trees that have pre-existing symptoms so as to not confuse these with subsequent treatment effects.  Four symptom classes are recognized ranging from healthy to moribund.  Determinants involved in these crown symptom classes are based upon foliar color, needle/leaf size, and internode length, with chlorosis and off-green color being the primary character defining symptomatic trees.  Only conifers are included in this study.

Woody root samples are taken from symptomatic trees.  Root samples are not taken from identified symptomatic trees until and unless the insect flight season has passed.  Two symptomatic trees and one asymptomatic tree are sampled from each sample plot.

In the laboratory sections from each root are placed on plates with malt extract agar andplates with malt extract agar with the addition of 200 ppm cycloheximide for culturing.  The plates are incubated for at least 10 days and visually inspected for fungal colonies.  

Since most of the study plots are located on sites with clay soils and these stands are especially predisposed to littleleaf disease, additional fungal isolations, specifically for P. cinnamomi, will be done after treatment implementation.  Root sampling will be conducted on eastern red cedar in plots which have a high sand component, and which contain symptomatic trees.  Resulting root cultures will be examined for presence of H. annosum.  

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