White cotton like mold on weeping crab #772753 - Ask Extension


White cotton like mold on weeping crab #772753

Asked September 22, 2021, 6:30 PM EDT

I noticed my mature weeping crab was looking sick. It has a white cotton like mold covering the branches. This past spring, much of the inner branches were dead and there hasn't been a typical amount of growth this year. What is on it and how to I save it? Thank you so much for your help!

Ottawa County Michigan

Expert Response

Hello Jeremy

The pictures aren’t clear enough to tell if this is an aphid insect, a mealybug or a scale insect. All may affect apple and crabapple species but, each insect might need different treatment.

There are a couple ways to get a diagnosis, and with that you will know how and when to control the insects.

Email the MSU Diagnostic Lab at pestid@msu.edu

Submit clear pictures of:

  1. the whole tree including the trunk and the entire canopy,
  2. along with close up pictures you have here.
  3. Try again to get an even closer clear picture of the white substance- carefully brush away the fuzz to see if any insects or “bumps” are visible below the fuzz. If you have a macro lens for your camera, or can hold a magnifier over the camera lens, this might help. Go for a clear picture farther back, rather than a blurry shot.

They will give you an opinion along with treatments, if they can diagnose the tree. They may request a branch sample or a sample of the “fuzz”.

Another way to get a diagnosis is hire a certified arborist, a professional who has taken training in care, diseases, pests and passed certification tests. He/she will come on site and give a complete diagnosis and a plant care plan. Find certified arborists by zip code here—-


See these references for pictures of the type of insects that have these white fuzzy appearances




Laura Sheffer Replied September 22, 2021, 9:46 PM EDT

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