Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Applied and Environmental Biology

Committee Chair

William L. MacDonald.


Historically, hypovirulent strains of Cryphonectria parasitica have been introduced into cankers principally by inoculating wounds made to the margin of cankers. Twelve hypovirus introduction methods were tested. Seventy-two trees were inoculated in June 2002 with an orange-pigmented virulent strain of C. parasitica (two inoculations per tree). After 11 weeks, the resulting cankers were treated with a brown-pigmented hypovirulent C. parasitica isolate using one of the following methods: (1) a non-invasive treatment where the inoculum was painted onto the canker surface; (2) an invasive treatment where the canker face was wounded with a sharp blade prior to the painting application of the hypoviruses; and, (3) a margin punch treatment where a series of wounds were made around the canker perimeter and filled with inoculum of the hypovirulent strain. Additionally, half the cankers in each treatment were covered to keep treatment inoculum moist and to protect treatment inoculum from biotic and abiotic factors. Isolates that were vegetatively compatible or incompatible with the canker inciting strain were employed. Hypovirus transmission was evaluated in November 2002 and May 2003 by culturing bark plug samples and evaluating the pigmentation and morphologies of isolates recovered. Canker dimensions also were recorded to determine if hypovirus transmission had an affect on canker expansion. (Abstract shortened by UMI.).