Scale on Eastern Redbud

(Question)

Hello. I live in London, Ontario and have an approximately 14 year old Eastern Redbud that has developed scales this season. They seem very abundant on one side of the tree and I’m guessing if it goes untreated it will consume the whole tree. How and when should I treat it? Also, I’m not sure if this is related to the scale or not but the bark on the main trunk has been coming off in large pieces all summer. Is this just a normal growth symptom or is something else possibly causing it. The underlying trunk doesn’t really look unhealthy. We did a significant root pruning in the spring.
I appreciate any and all advice.

(Answer)

 

Thank you for your question about your Eastern Redbud, or Cercis canadensis. Those pesky scale insects seem to arrive overnight. The best time to treat them is in their ‘crawler’ stage, in the Spring before they settle on a spot and grow an armoured shell. A good diagnostic tool to determine when they arrive in spring and early summer is to wrap some black tape on a branch, such as electrical tape, sticky side out, which will enable you to see the juveniles and to know when to apply horticultural oil to smother them. Unfortunately the protected mature scale will not be affected unless you can scrape some of them off the branches.

The exfoliating bark is a characteristic of this tree. You mention that the underlying bark is healthy. The spring root pruning should have had no effect on the bark, but will necessitate increased watering to accommodate fewer roots.

Your ongoing good cultivation could include a 2 to 4″ (5 to 10 cm) of organic mulch, both for nutrition and to conserve moisture, but it should kept away from the tree trunk to avoid disease. The Redbud is a legume so naturally fixes nitrogen in the soil.

The following publications will examine the topics more thoroughly.

Good luck with your tree and enjoy it for many years to come.

 

https://www.torontomastergardeners.ca/askagardener/bark-damage-to-eastern-redbud/

https://www.bio.brandeis.edu/fieldbio/Edible_plants/EasternRedbud/EasternRedbud.html

https://extension.entm.purdue.edu/publications/E-29.pdf