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Question from Deborah, Clearfield, UT (received 5/26/20) -
We have three green vase zelkova trees in our backyard that we planted over 12 years ago. All of the trees have been doing well, but recently one tree has leaves that are changing color- they are no longer a nice green color but a light/pale yellow- almost translucent. Not all of the leaves on the tree have changed, just a few branches worth. Any thoughts on what we need to do to help our tree? Thanks!
Answer from Gabrielle Harden, USU Forestry Extension Educator (sent 5/27/20) -
Deborah,
At first glance, my mind goes to iron chlorosis. This is common in our region as our soils have a higher pH and therefore lack iron. However, then I saw the picture of the white spots found on the branch. That appears to be European Elm Scale. The zelkova is part of the Ulmaceae family, same as the elms. Have you started noticing any honeydew on surfaces below the tree such as patio furniture or a parked car?
Scale feeds on the sap found in twigs and leaves. Scale can cause leaf yellowing and early leaf drop. If possible, get in for a closer look to determine how bad the infestation is. Heavy infestations can cause branch dieback. Treatment is possible with horticultural oils or insecticides.
Here are a couple of links that will be useful for you -
It is important to reduce stress on the tree. This means providing adequate water (trees need to be deeply watered - drip lines and sprinklers typically can not provide deep enough watering).
I hope this helps.