Early yellowing and leaf drop on Mature Cherry tree
Why are the leaves on my mature sour cherry tree dropping in August? Love this tree and want to save if possible. There is no powdery mildew, or noticeable insects. Leaves are just turning yellow and dropping off. Noticed a lot of fruit trees in the area also yellowing and dropping their leaves early.
Rock County Wisconsin
Early yellowing of tree leaves is usually an indication of problems.
Possible causes are: 1) Overwatering can cause yellowing. This could be due to a variety of reasons, but one example is that cherry trees planted in lawns tend to get too much water. If this is your problem, stop watering the lawn near the tree. Remove the grass over the root area of your cherry tree, and replace it with 2 to 4 inches of mulch. Don't pile the mulch up against trunk bark, where it will cause rot and create new problems. Then water the tree every three weeks, allowing it to dry out considerably between waterings. 2) Iron chlorosis causes yellowing of leaves due an iron deficiency. Yellowing due to low iron starts at the edges of the leaf, moving to the center. Veins tend to remain green throughout this process and make it easy to identify this cause. However, iron chlorosis is difficult to treat and simply adding iron to the soil doesn't really help. Good cultural practices like aerating soil, amending clay soil with peat and organic compost and reducing springtime watering are often more effective. 3) Diseases or insects - a) Bacterial spot of cherry is a fungal disease caused by the bacterium Xanthomonas pruni that causes extensive foliar damage. The disease favors heavy rain, wind and wet weather conditions for infection and spread. Symptoms of bacterial spot consist of water-soaked leaf spots with a brown to black color, leaf yellowing, numerous small holes on leaf surfaces and leaf drop. Infection can spread to the cherry fruit, causing dark brown spots and a sunken appearance. b) Cherry tree leaf spot, caused by the fungus Blumeriella jappi, is a disease of cherry foliage and fruit. The fungus favors wet, humid conditions for infection and temperatures between 60 to 68 degrees F. Small purple to brown leaf spots, leaf yellowing, leaf drop and small holes where leaf spots initially formed identify cherry leaf spot on foliage.
Here is a link with some photos and descriptions of the most common diseases:
I hope this is helpful. Please contact AaE again if you have further questions.