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The leaves of our sweet cherry tree have yellowed and our falling off at an alarming rate. This started two weeks ago and in another week ALL the leaves will have dropped except for a few on the tips of new growth (i.e. water spouts). This happened last year to two of our other sweet cherry trees. They did NOT come back this spring. Dead! The trees are 25 years old and pruned yearly. I've been fairly diligent about spraying (dormant oil, fruit fly, and borer) for the six years I've owned the house. At times they have shown signs of borer (or other insect) damage since there has been gumming spots on the trees. When I bought the house I removed the grass around the trees (not quite to the drip line,but a about four feet from the trunk. The trees get water from the lawn sprinklers, but I regularly (every 2-3 weeks) let a hose run water around the tree and soak in for a couple hours. When I fertilize the garden (commercial IFA garden chemical fertilizer)I toss a couple handfuls at the base of each tree. So some fertilizer about twice a year. The soil around the house is mixed. I would guess that most of it is moderate clay. We live on the edge of the bench not far from the mouth of Hobble Creek Canyon. If I had just walked into the yard, I would guess that the trees were getting too much water (yellowing leaves) instead of not enough water (dry crisping leaves). But I really don't water the trees that much and not at all in the last couple weeks when this yellow & leaf drop started. My only other clue is some leaves have brown spots. About the time we bought the house, a neighbor had a cherry tree drop most of its leaves and they were told (USU ext?) that it was a fungus; they sprayed and saved the tree. They've moved so I can't ask them specifics. I don't remember if the leaves had yellowed and then dropped. Too long ago. Help?

Answer(s)

A

There are several reasons why a cherry tree might drop its leaves.  I suggest that you check your watering first.  Trees do best with a deep soak once every one to two weeks. Because   your trees are in your lawn they are probably getting too much water.  Overwatering can cause yellowing and leaf drop as well as poor growth in general.

Since you say that you have seen gumming spots on the trees, it is possible that you do have a problem with borers.  Once crown borers are in the tree there is not much you can do except try to maintain good vigor and hope that the tree will not be badly damaged.  Your tree should be sprayed for borers at the beginning of July and again at the beginning of August.  Make sure you get thorough coverage on the trunk from the lower branches down onto the soil line.

There is a fungal disease of stone fruits called coryneum blight.  It can cause small holes in the leaves and can also infect the twigs and damage the bark.  This may be the fungal disease that your neighbors treated for.  One of the diagnosticians can check for this if you bring in some sample twigs from the tree.  We charge one dollar to do a diagnosis.

It would be good to take a few minutes and also check your trees for mites.  A heavy infestation of mights can also cause leaf drop.

Please call us at 801-851-8462 if you have more questions.

Posted on 6 Aug 2008

Pat Fugal
Horticulture Assistant, Master Gardner, Utah County

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