Hi Mark,

I'm sorry to hear about your crabapple!

From what I can see in the photos, it looks like your tree has powdery mildew, a fungus that grows on the surface of leaves and twigs but that is not systemic in the tree (ie, it's not spreading within the tree, it is being splashed or blown from place to place).

Fireblight symptoms do not include white fuzz; you would see distorted leaves and twigs turning black.

For powdery  mildew, you can prune out the infected portions and help slow the spread of the fungus.  Some chemical options are available, including potassium bicarbonate, neem oil, and fungicides labeled for powdery mildew.  Chemicals will help prevent additional infections and may kill existing infections, but the distortions of growth won't recover.  For long-term control, try to improve air circulation around the tree and be sure to clean up fallen leaves; the fungus overwinters there.  

I hope this is helpful!

Cordially,

John

Hi John, Thanks for your response it was very helpful. My heart sank when I thought it was fire blight. I have attached another photo of the same tree. I have Nuthatch birds nesting in a dead limb. In reading about fire blight, an article mentioned a sappy liquid may be present. If you look closely at the entrance to the nest you’ll see what I’m talking about. Is this a concern? 

Hi Mark,

Fire blight relies on living tissue; it will not infect dead wood.  If that limb is dead, then there's no risk of disease and I suspect that the fluid is bird-related, at least indirectly.  The opening in the wood may provide an avenue for decay organisms to enter and rot the branch and the center of the tree, but the trade-off of wildlife habitat may be worth it to you!

When fire blight infections are new, the tissue that is infected may appear to be wet (or "water-soaked"), but you won't actually see fluid dripping from the tree.  The base of the leaves of figure 1 in this fact sheet give an idea of what this can look like: https://extension.colostate.edu/docs/pubs/garden/02907.pdf

I hope this helps!

Cordially,

John

John, Once again thank you for your quick response and information you provided.