Viability and dispersal of ascospores of Anisogramma anomala, the cause of eastern filbert blight (EFB) on European hazelnut, from diseased branches pruned from trees were measured. In each of two years, branches bearing stromata of A. anomala were cut in mid-December and compared to branches cut near budbreak in March, when trees became susceptible to infection. The experiment was replicated three times at separated locations. At each location, 125 diseased branches (source) were piled loosely in a 1 x 1 m area. From March to June, spore traps (rain sampling-type) as well as 2-year-old potted hazelnut trees were placed next to each source, 6.4 m upwind and downwind, and 20 m downwind from each source. During seven significant major rain events over the two seasons, hazelnut seedlings (3-month-old) were placed adjacent to the spore traps. Near sources significantly higher (P. < 0.01) ascospores counts were obtained for branches cut near budbreak compared to those pruned in December in the first season; no significant difference in counts of ascospores were observed in the second season between pruning treatments. For both seasons significantly higher (P < 0.05) counts of ascospores were observed at 6.4 m downwind compared to 6.4 m upwind or 20 m downwind of a source. Ascospore viability, as assessed by staining with trypan blue, was similar for both pruning times at all distances and averaged 50%. At least one infected seedling was obtained for 5 of 7 major rain events regardless of pruning time at sources and 3 of 7 major rain events 6.4 m downwind of a source. All of the 2-year-old potted trees for both pruning treatments at the source and 6.4 m downwind became diseased and > 50% of trees at 20 m downwind became diseased in the 2010 season. Similar to ascospores counts, disease incidence was significantly higher (P < 0.01) in 2-year-old potted trees observed 6.4 m downwind compared to 6.4 m upwind or 20 m downwind in the 2010 season. Significantly higher (P < 0.01) disease incidence in 2-year-old potted trees was observed 20 m downwind compared to 6.4 m upwind in the 2010 season. Downwind disease gradients for both pruning treatments were shallow with slopes that were not significantly different than zero (p > 0.05) for the 2010 season. Based on these results, ascospores from diseased branches pruned from trees in both pruning treatments remained viable, infectious and were dispersed downwind of each treatment. / Graduation date: 2012

Lygodium microphyllum, native to the Old World tropics, has invaded central and southern Florida, destroying native habitats, reducing biodiversity and altering fire regimes. Prescribed fire, one of several methods used to manage L. microphyllum infestations, reduces fern biomass over large areas, but its effects on spore viability are unknown. To provide tools to evaluate whether fire-dispersed spores are viable, this research determined how heat affects spore viability. Spores were exposed to temperatures of 50°C to 300°C for durations of 5 seconds to 1 hour, then allowed to germinate on agar in petri plates. Percent germination was assayed after two weeks. Temperatures of 50°C had little effect; 300°C killed spores for all durations. Results indicate that while viability of unburnt spores decreases with increasing temperature and duration of heat exposure, spores are killed when exposed to relatively low temperatures compared to those in fires.