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Poster: Epidemiology: Risk Assessment


Symptomatology and epidemiology of Exobasidium leaf and fruit spot of blueberry
R. INGRAM (1), H. Scherm (1), R. Allen (1) (1) University of Georgia, U.S.A.

Over the past decade, Georgia has become one of the largest producers of cultivated blueberries in the United States. As production has expanded, several new blueberry diseases have emerged, with Exobasidium leaf and fruit spot caused by the fungal pathogen Exobasidium maculosum being the most recent. The disease causes early-season leaf spotting and green spots on fruit. The pathogen produces both basidiospores and yeast cells, but its life cycle, including its overwintering biology and primary and secondary inocula, is unknown. Epidemiological field studies initiated in 2014 included the use of trap plants, a leaf spot demography study, spore trapping, and epiphytic population enumeration. Monitoring of surface populations showed that E. maculosum is capable of overwintering epiphytically on all blueberry tissues tested during dormancy. Demography and trap plant data collected in 2015 suggested that dispersal of primary inoculum occurs shortly after leaf/flower emergence, and that infection of primarily young and tender tissue is favored by prolonged rainy periods (>3 days/week). Disease progress in 2015 indicated that the disease is active from March through late May, and that initial fruit and leaf infection occur simultaneously. Additional observations revealed a novel symptom, lesions on emerging shoots that cause girdling and blighting. Although initial results suggest that the disease is monocyclic, further confirmatory studies are needed.