Why is my tree dropping leaves in the summer?
Here it is the first week of August in Sioux Falls and we are praying for rain. The weather men keep trying to give us hope that it might rain, but it’s not. So far in 2016 the spring was wet and cool. May was really wet with a lot of good rain to soak up the soil. That cool and wet weather lent the way to a lot of foliar fungal infections to a wide variety of trees and shrubs. Since then (early June) we have been abnormally dry with little rain in Sioux Falls and areas south west of the city. We have also had a lot of very HOT spells. All of this is leading to a stress on trees that is starting to show up now in the form of some trees dropping yellow leaves.
For birch, hackberry, boxelder, locust, buckeye, and some other species of trees in dry periods during the growing season they will drop interior leaves (usually yellow) to help conserve water. It is a sign of slight stress so effective watering during these dry periods will help keep the trees healthy long term, but it will likely not stop the dropping of the yellow leaves in the short term.
For your other trees like apple, maple, aspen, and pears where the leaves have brown spots on the leaves and they are dropping leaves, that is typically a sign of a fungal infection of the leaves. These infections are usually harmless in a once in a while type of way, but if they happen bad enough in successive years, they can start affecting overall tree health. The treatment protocols for foliar fungal infections is preventative only. Once the damage is apparent in the spring or mid summer, it is too late to anything about it. If you have trees with this issue constantly, you will need to have them sprayed in the early spring when the new growth is emerging at designated intervals to protect the new growth. Timing of those sprays is the most critical portion of controlling fungal infections.
If you have questions with your trees and need information on what is attacking them or if they are sick or healthy, contact me today for a consultation so you can have the best information relating to your trees so you can make the best informed decision with caring for your trees.
Sam Kezar, ISA Board Certified Master Arborist (MW 4503B)