By Tilly3006
Lancashire,
United Kingdom 
what is this on my willow tree?
Hi, i have 2 kilmarnock willows which i adore. They are both suffering from rust, which i know they can be prone too. But on the underside of the leaves i have noticed white/cream ball type growths which are raised, as seen in the photos. Is this part of the rust, or do i need to be concerned? thanks
19 Jun, 2011
Answers
Sorry Bamboo, its a Gall Wasp.
But still doesn't really cause the tree any harm.
19 Jun, 2011
thanks both of you. Should i pick the leaves off that are infected?
19 Jun, 2011
No need really. If its just a few you could.
19 Jun, 2011
Well, gall mites, gall wasp, still a gall, lol! I didn't check which particular beastie might cause it, to be honest...
20 Jun, 2011
Caused by gall mites - provided the infestation isn't extremely heavy, no harm to the plant results from these. Unrelated to the rust condition.
19 Jun, 2011