Q.Japanese Cherry Tree Early Discoloration Of Leaves
We have had hot weather around 85F for about 10 days and I would set my lawn sprinkler to water the lawn and the cherry tree for about 45 minutes every other day. Sometimes I’d water at night so evaporation would be less. Now,in cooler weather and smoke from distant fires, I’m noticing purple-brown patches on the leaves. Some leaves on individual branches have died. I don’t think I’ve overwatered, since we had a wet April and May and the tree was fine. These leaves are still soft, not brittle, but they’ll eventually die. I don’t think I’ve underwatered either. I’ve had the tree for five or six years and I’ve never seen this. Please see attached photos.
Certified GKH Gardening Expert
85 is, particularly, ideal for these trees. Watering every other day will be excessive, on its own. Watering at night when the temperatures are ideal for living organisms, including pathogens, will be the ideal breeding ground for those pathogens.
Damage from wet weather can takes weeks, to a couple of months to show up. Usually, incubation happens during the warmer months, if there is enough moisture, and will enter reproduction phase, just as it begins to cool off.
Your description of care will indicate that the tree has contracted a blight from overly wet conditions, as well as being an ideal breeding ground for these pathogens. There are several that can appear in this fashion, but this resembles Verticillium Wilt, or Fire Blight. Both can exhibit similar symptoms. Here are some articles that will help:
https://www.gardeningknowhow.com/plant-problems/disease/verticillium-wilt-treatment.htm
https://www.gardeningknowhow.com/plant-problems/disease/fire-blight-remedies-and-symptoms.htm
Your local extension service can pin down the exact pest with microscopy. This article will help you to find the closest to you:
