UGA Blueberry Blog

Mummy Berry Threat is High

In the southern region of the state, leaf emergence on blueberries coupled with recent rains and warmer temps leads to the question of whether mummy berry will be an issue (infections at green tip or early bloom, whichever comes first).  Mummy berry disease epidemics 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 is synchronized with leaf development in rabbiteye blueberries.  Therefore, on rabbiteye blueberries, fungicides with activity against mummy berry should be applied starting at green tip or early bloom, whichever comes first.

Regarding southern highbush varieties, if the leaf tissue is at green tip or early emergence, it can be infected with mummy berry as well.  Prior work in Georgia has not confirmed mummy berry on southern highbush varieties in Georgia, since most of the time southern highbush varieties here escape the initial infections due to earlier plant development.  However, some highbush varieties elsewhere in the southeast can be severely affected, and if the correct environmental conditions occur on southern highbush varieties in Georgia, it should be assumed that these can likely develop mummy berry as well.

Given where we are in terms of chilling and soil moisture, and with the recent bout of warmer and wetter weather, we have ideal conditions for disease development. According to John Ed Smith (MBG), “Early and mid season rabbiteye are already showing green tip; early season rabbiteye are showing early signs of bloom; and early highbush are 40-50% bloom.”  Therefore, producers should be applying mummy berry sprays, and any blueberries at the correct stage (green tip and early-bloom [bud break] and continuing through bloom) should be assumed to be susceptible. For additional information on fungicides which are available for management of mummy berry, refer to the Southeast Regional Blueberry Integrated Management Guide at www.smallfruits.org.

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About Jonathan Oliver

Dr. Jonathan Oliver is an Assistant Professor and Extension Specialist in the Department of Plant Pathology at the University of Georgia. He has a 75% research and 25% extension appointment. Dr. Oliver started in his current position at the University of Georgia in mid-2017 as an extension fruit pathologist at the Coastal Plains Experiment Station in Tifton, Georgia. His responsibilities include research and extension activities focused on pathogen biology and disease management in fruit crops grown primarily in the southern part of Georgia, including blueberries, blackberries, citrus, and other emerging fruit crops. Dr. Oliver obtained a BS degree in Plant Pathology and Microbiology & Cell Science from the University of Florida in 2005, and a PhD in Plant Microbe Biology from Cornell University, New York State Agricultural Experiment Station in Geneva, NY in 2011. In addition, he has also been postdoctoral researcher at Kansas State University and Auburn University. At Auburn, he characterized the interactions between the emerging bacterial pathogen, Xylella fastidiosa, and its blueberry plant hosts. He currently serves as a Plant Pathology Section editor for the Southeast Regional Blueberry Integrated Management Guide.