Issue 3, May 20, 2019

Maple Leaf Blister

Maple leaf blister commonly infects silver and red maples as well as their hybrids. Outbreaks usually occur during springs with extended cool, wet weather. This disease is closely related to peach leaf curl, plum pockets, and oak leaf blister, all of which are caused by fungal pathogens belonging to the genus Taphrina. This group of pathogens infects leaves early in their development, often at the time of bud-break.  As the leaves mature, they become resistant to the fungus, so there is effectively one infection cycle per year. The fungal pathogen causes abnormal cell division and enlargement, which can cause infected leaves to have a blistered, crinkled appearance.  The blisters are initially green but quickly transition a brownish-black color.  Anthracnose infections are also likely, given this spring’s predominately cool, wet weather. One way to distinguish a Taphrina infection from an anthracnose infection is that Taphrina usually does not cross leaf veins or infect the leaf petiole. 

Maple Leaf Blister

Maple Leaf Blister (University of Illinois Plant Clinic)

Leaf blister diseases generally do not warrant control. Any injury caused by these diseases is mostly aesthetic, and not will harm the long-term health of the tree.  Leaf blisters may cause some defoliation, but a new flush of leaves emerges will in warmer and drier weather. Several fungicides are labeled to control Taphrina diseases, but their use is generally limited to fruit orchards. Additionally, fungicides are preventive and won’t have any effect on current infections.

Travis Cleveland

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