my oak tree is losing branches where the attach to larger branches - Ask Extension
What should I use to stop my oak tree from losing branches in the spring and summer. The branches are usually small and break off from a larger bran...
Knowledgebase
my oak tree is losing branches where the attach to larger branches #367144
Asked October 01, 2016, 3:52 PM EDT
What should I use to stop my oak tree from losing branches in the spring and summer. The branches are usually small and break off from a larger branch at the base. It appears that there is some insect activity right at the base of the leaf branch--sorry I don't know more of the proper lingo--but, let's say we have a branch with 5 to 12 leaves on it--the whole branch breaks off right at the place where it joins the larger branch. It does not seem to be threatening the tree's health, this year. Last year, it did appear to be widespread and I sprayed it with a heavy oil. Unfortunately, I was not careful enough and got pretty sick. I now understand the safety precautions attached to the heavy oil--and will follow them more carefully. IS the heavy oil the right treatment for this seemingly insect driven loss of branches? I am relatively certain the tree is a Red Oak--the leaf has 9 sharp pointed ends.
Denver CountyColorado
Expert Response
From this photo, It is difficult to determine what the insect might be that is infesting the tree. However, if you could bring a branch and leaf specimen as well as photos of the tree, into the DBG Library, Garden Help Line or to the local CSU Extension Center located at 888 East Illiff, Denver, an insect identification can be made using a microscope. Without proper insect identification, it is difficult to say that a "heavy oil" is the appropriate treatment for this oak tree.
This occurs in the spring when new branches start emerging, or when very small branch begin to grow. Obviously, there is nothing I can do at this time. My effort was to provide you with a leaf that would identify the tree--not the insect. I came across an article that stated that an insect laid eggs in the joint of a newly formed branch and that as the insect hatched, it caused the branch to break cleanly off at the source--it described it perfectly. However, I did not mark it--thought maybe you folks would have some idea. For some reason, the phrase "leafwig" sticks in my mind.....There is nothing I can do at this time, does not appear that you are familiar with any insect that would lay eggs in a branch joint--so, thank you for your effort.
Oaks are loosely divided into 'red oaks' with pointy lobes and 'white oaks' with rounded lobes. The one in the photo is from the red oak group, and, if it's here in Denver, it is most likely Red Oak (Quercus rubra).
The twig dieback you've experienced is mostly likely caused by a scale insect called Kermes Scale. The overwintering stage is concentrated around the buds. Next year the insect will feed on the new shoot growth. They will continue to feed for several months, becoming full-grown in June or July. After mating, the females lay eggs which by late summer are about the size of a marble. The eggs hatch in September and October and the 'crawlers' move to their over-wintering spots, and the whole cycle starts again.
Yes, you can control scale using horticultural oil (like All Seasons® or Fertilome Dormant Oil Spray) applied in the fall during the crawler stage and/or in the dormant season during the over-wintering stage. Crawlers also may be controlled with various pyrethroid insecticides and imidacloprid (Bayer® Tree & Shrub Insect Control).
