While the upcoming forecasted freeze event is understandably foremost on the minds of those connected to the Georgia blueberry industry right now, diseases associated with bloom remain a concern. Many growers in the southern region of Georgia have initiated sprays for mummy berry disease already, but growers who haven’t already done so are reminded to initiate sprays for mummy berry to protect vulnerable plants. According to the mummy berry model developed by Dr. Harald Scherm (UGA), we are currently at HIGH RISK for mummy berry disease initiation in southern Georgia. Blueberry plants are vulnerable to initial infection with mummy berry when they are at green tip and/or early-bloom [bud break], and plants will remain vulnerable to infection throughout the bloom period.
Epidemics of mummy berry disease are set-up by the synchronized release of fungal ascospores and the emergence of green leaves in blueberries, which leads to subsequent leaf strikes. Since the fungus that causes the epidemic has similar chill-hour requirements for germination to the chill-hour requirements for native blueberry species, this means that ascospore release in southern Georgia is typically synchronized with leaf development in rabbiteye blueberries in southern Georgia. Initial infections typically occur when rabbiteye varieties reach green tip or early bloom (whichever comes first). Regarding southern highbush (SHB) varieties, if the leaf tissue is at green tip or early emergence, it can be infected with mummy berry as well.
Typically, in southern Georgia, SHB blueberries escape the initial infections with mummy berry due to earlier plant development, and many of our SHB cultivars are already past bloom in many locations. Nonetheless, any cultivars that are currently at bloom are potentially susceptible to mummy berry at this time. For management of mummy berry on susceptible blueberries, fungicides with activity against mummy berry should be applied starting at green tip or early bloom, and 2-3 further applications are typically recommended during the bloom period. Additional information on fungicides which are available for management of mummy berry can be found in the Southeast Regional Blueberry Integrated Management Guide at www.smallfruits.org.