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Poster: Epidemiology: Pathogen Dispersal


Field observations of ascospore discharge of Monilinia vaccinii-corymbosi in northern highbush blueberries
G. Dabbah (1), A. Schilder (2) (1) CSU Monterey Bay, U.S.A.; (2) Michigan State University, Department of Plant, Soil and Microbial Sciences, U.S.A.

Monilinia vaccinii-corymbosi (Mvc), is the causal agent of a disease known as mummy berry in highbush blueberries (Vaccinium corymbosum L.). The primary inoculum of Mvc is discharged from apothecia grown from mummified blueberry fruits that fall to the ground in previous seasons. In order to better predict the release of primary inoculum a study of ascospore discharge was conducted using aerial spore trapping and several weather variables. A Burkard spore trap was used to collect ascospores within infested blueberry fields in 2002, 2003, 2004, and 2009. A previously developed degree-day model was also assessed in order to compare the amount of chill-hours and degree-days required for southwest Michigan grown blueberries. Peak ascospore discharge was inversely related to daily relative humidity and the majority of ascospores were discharged between 67-107 growing degree-days and after 3000 chill-hours were attained. Additionally, peak ascospore discharge was reached when apothecial cup size was between 2-7mm in diameter which correlated with previous laboratory studies. The information in the study may be used to better understand the conditions needed to predict mummy berry apothecia emergence and ascospore discharge with the aim of improving future disease management practices.