Inoculations with the prime suspect pathogens will be performed to assess their relative aggressiveness under controlled conditions, and possible interactions that may exacerbate decline. Genetic variation in host susceptibility to these pathogens will be assessed. Sweetgum dieback after planting is a common problem. Preliminary isolations from dying seedlings have yielded Botryosphaeria dothidea . Fungi in the genus Botryosphaeria are considered facultative parasites with a broad host range.
Inoculum is probably uniformly present, and genetic variation among isolates is considerable.
The first approach to defense against such pathogens is to increase the vigor of the host. Manipulations of nursery or cultural practices should be tested to reduce losses at transplanting. These projects will be conducted in collaboration with SRS-4155, the NC State Hardwood Coop, and forest industry. Develop a method for rapid resistance screening to the most important pests of sycamore. Determine, as far as possible, what basic underlying mechanisms contribute to host susceptibility or resistance to sycamore decline.