The past two months have been relatively wet and cool to warm. This prolonged period of overcast conditions, high humidity, and light to moderate rainfall is perfect for some of our foliar disease issues. “April flowers bring May Leaf spots” doesn’t have the right ring to it, but we are seeing quite a bit of leaf curl and leaf blister. These are two disease issues caused by Taphrina spp. fungi. Like the common names of their diseases, the symptoms caused by a Taphrina infection include leaf deformation.
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- Figure 1: Peach trees showing symptoms of peach leaf curl caused by Taphrina
In the case of Peach, the leaves turn light yellow, bright pink, or red where tissue puckers and twists leading to curled leaves. In oak, leaves develop localized blisters that are light green early in the season and are easy to miss since the color is not very different from healthy tissue. However, the blisters will turn brown later in the season which makes them more noticeable. Maples also get a disease caused by Taphrina, but it does not cause as much distortion as it does on oak or peach. Severe maple leaf blister can lead to leaves becoming slightly contorted, but the primary symptom is brown necrotic lesions.
Figure 2: Oak leaf blister symptoms ranging from light green early infections, changing to yellow and then becoming necrotic as the season progresses.
With cool wet weather over an extended period of time, we have been seeing more foliar disease issues than in the last few years. Since disease problems can take time to develop, Taphrina is likely just the harbinger for some other disease issues we may see in early summer if moderate conditions continue. If the weather dries out as it heats up, it will halt many of these foliar problems in their tracks.
Figure 3: Symptoms of leaf blister on maple trees.
