Hawthorne gall

[Zac]

This is my first year spraying crabs and hawthornes. I have noticed that many hawthornes seem to have a gall on the end of the twigs. Is this caused by the fungal rust?

 

[Tree Wizard]

Pictures would be nice to know for sure, but you are probably seeing the effects of cedar-quince rust.

 

[Urban Forester]

The 'galls' on hawthorn twigs are more than likely one of the Globosum fungi (Gymnosporangium Rust diseases) There are 3 distinct fungi that attack hawthorns. If the galls are on the twigs it's most likely G. Clavipes (Quince Rust) The alternate host for the maturing fungi is junipers and they are within 1/4 mile of the tree. Chemical control of Quince Rust is very difficult as the infection period can be long.