Issue 4, June 1, 2020
Maple Leaf Blister
Outbreaks of maple leaf blister were previously considered to be uncommon, occurring only during springs with extended cool, wet weather. However, those conditions have become more prevalent in recent years. As a result, we see outbreaks of maple leaf blister on a more frequent basis.
Maple leaf blister infects silver and red maples as well as their hybrids. 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. Mature leaves are resistant to the fungus, so there is effectively one infection cycle per year. The fungal pathogen causes abnormal cell division and enlargement, which results in a blistered, crinkled appearance to infected leaves. Maple leaf blister lesions are initially green but quickly transition a brownish-black color. From my observations, the blisters seem to collapse as they transition in color, and quickly lose their raised appearance.
Maples leaf blister can easily be confused with anthracnose infections. Both diseases can occur on the sample tree and leaf, adding complications to the diagnosis. The best way to distinguish the two diseases is with a microscope. However, the majority of us don’t have access to one. I’ve come across a couple of suggestions to help distinguish the two diseases. 1) Maple leaf blister lesions have a somewhat rounded shape, compared to irregular and angular anthracnose lesions. 2) Maple leaf blister lesions usually do not cross leaf veins or infect the leaf petiole.
Maple Leaf Blister
Maple Leaf Blister (University of Illinois Plant Clinic)
The injury caused by maple leaf blister is mostly aesthetic, and not will harm the long-term health of the tree. The disease may cause some defoliation, but a new flush of leaves will emerge in warmer and drier weather. Leaf blister diseases generally do not warrant control. Several fungicides are labeled to control Taphrina diseases, but their use is usually limited to fruit orchards. Additionally, fungicides are preventive and won’t have any effect on current infections.
Author:
Travis Cleveland