Recent warmer, damp weather has led blueberry growers in the southern region of Georgia to initiate sprays for mummy berry disease. According to the mummy berry model developed by Dr. Harald Scherm (UGA), there is a HIGH RISK for mummy berry disease initiation in southern Georgia as of February 15th, 2021. Growers who haven’t already done so are reminded to initiate sprays for mummy berry at this time to protect vulnerable plants. (Blueberry plants are vulnerable to initial infection with mummy berry when they are at green tip and/or early-bloom [bud break]. Plants will remain vulnerable to infection throughout bloom.)
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. 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. However, relative to recent years, southern highbush development this year in many locations across the southern part of Georgia has been noted to be somewhat behind (delayed), meaning that many southern highbush may now only be at green tip or early bloom. This may make SHB in southern Georgia more susceptible to mummy berry in 2021 than in a typical year when they would have already bloomed prior to mummy berry ascospore release. For management of mummy berry on susceptible blueberries, fungicides with activity against mummy berry should be applied starting at green tip or early bloom, whichever comes first. 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.
