Blueberries passed peaches as the state’s top moneymaking fruit a few years ago, worth more than $100 million on the farm annually. But new diseases threaten the popular berry, says a University of Georgia fruit specialist.

Blueberry necrotic ring blotch disorder and bacterial leaf scorch, are new to Georgia's blueberry crop, said Phil Brannen, a plant pathologist with the UGA College of Agricultural and Environmental Sciences.

“We are seeing two new diseases causing concern for growers with southern highbush blueberry varieties,” Brannen said. “Traditional, native varieties seem to be resistant to both diseases.”

Southern highbush varieties ripen in April and May, returning a high profit for growers during the spring market. The native rabbiteye varieties ripen in June and July for the summer market.

Blueberry necrotic ring blotch disorder causes the plant to lose its leaves, defoliating long before berries are ready to be harvested. Some plants with the disease defoliate twice a season, Brannen said. So far, individual plants aren’t dying, but yields have been cut.

Necrotic ring blotch is likely caused by one or more viruses, but the verdict is still out on this unusual disease. “In places where we saw severe epidemics in 2008, we don’t see it at all today, which is unusual for a virus. We don’t know if it will come back, or if it naturally works its way out of an area,” Brannen said. “We know very little about this disease right now.”

The disease first appeared in Georgia in 2006, the first reported place in the U.S. It has now been found in North Carolina, Florida, Mississippi and South Carolina.

“It could be a new disease introduced from another country or a mutation of an existing virus,” he said. “Without regard, it does happen, and we can’t rule any of this out.”

Brannen is working with Mike Deom, a UGA plant virologist, the United States Department of Agriculture and colleagues at the University of Arkansas to identify the virus.