Blueberry leaf rust identified in Mississippi

STARKVILLE, Miss. (WJTV) – Blueberry leaf rust has been identified on blueberries in Perry County, according to the Mississippi State University (MSU) Extension Service. Officials said everyone in the state with blueberries is asked to be on the lookout for this disease.

Alan Henn, MSU Extension Service plant pathologist, said leaf rust is not a common disease of blueberries in Mississippi, but it has been identified occasionally in several Mississippi counties over the past 10 years.

“Outbreaks tend to be localized but can be severe, causing defoliation and reduced yields,” Henn said.

Commercial blueberry growers in Mississippi typically offer rabbit's eye or southern highbush blueberry varieties, and these differ greatly in their susceptibility to leaf rust.

“The Bluecrisp, Climax, Delite, Emerald and Jewel varieties would be very susceptible, and the Powderblue and Star varieties would be moderately susceptible,” Henn said.

Officials say the fungus that causes blueberry leaf rust only survives on living plant tissue and therefore often does not survive Mississippi winters. Rust fungi have complicated life cycles, producing up to five types of spores on two different hosts.

Rebecca Melanson, Extension plant pathologist, said blueberry growers should inspect their fields for symptoms of blueberry leaf rust.

“Early symptoms on the upper leaf surface begin as yellow, chlorotic spots that enlarge into circles,” Melanson said. “As chlorotic spots age, the centers become reddish brown and the chlorotic zone shrinks to a narrow line surrounding the dark center. On the underside of the leaves, the area below the yellow spots will swell into a pustule that will eventually burst. The burst pustule releases visible orange-brown spores. In late fall and winter, black structures may be visible.

Overall, infected blueberry leaves may have a light green, chlorotic, or reddish appearance. In advanced infections, leaf edges may have brown, dead edges that may curl before falling to the ground.

Melanson said if blueberry leaf rust is detected or has been found in nearby areas, growers should include fungicides effective for blueberry leaf rust in their late-season and post-harvest spray program to fight against disease.

Blueberry leaf rust fungicides are listed in the Southeast Regional Integrated Blueberry Management Guide 2024, as well as in the MyIPM Fruit & Nut tool.