Spiky balls growing on oak tree

sim0n · December 09, 2013, 11:46:13 AM

Hi

I'm from Slovenia, at the top of the Adriatic sea, between Italy and Croatia. I've just joined this forum because I've been wondering about growths on a couple of oak trees around our house. It only seems to be present on two or three free-standing oaks in the vicinity of the house and its not on the huge oaks in our acre of forest.

You can judge from the photo below. They're fuzzy spikey balls about the size of a small lemon, amongst the leaves at the ends of branches. You can easily remove them. They don't really change colour through the seasons, always being the same slightly pinkish hue. The trees it's on have been looking a little weak lately but I'd appropriate that to two consecutive very very dry years.

I've googled for all kinds of oak parasites and diseases and lichens and couldn't find anything that matched. The closest thing going by description is ball moss but the colours and structure don't match. I checked the rest of the genus Tillandsia as well and didn't find anything. Should I be worried about them?

mesquite buckeye · December 09, 2013, 11:57:31 AM

I've never seen this one, but could it be a gall of some kind? We get galls that look kind of like this on other plant species caused by midges. That might be a place to start looking. ;D

sim0n · December 09, 2013, 12:32:08 PM

Here are two more photos of one that I brought inside and ripped apart. It was actually attacted onto the twig where a bud should be, and rather strongly by that so I may retract my earlier observation that they're easily removable.

I've been googling for photos of galls and more than anything, I am freaked out but all the strange growths plants can have.

But I think I've something that may be it: https://en.wikipedia.org/wiki/Diplolepis_rosae , but I'm still not sure because mine are on an oak tree, and we have some wild rose hip bushes which aren't affected at all.

mesquite buckeye · December 09, 2013, 04:29:00 PM

Most of the gall bugs have a fairly narrow host range. It does look a lot like the rose gall. It could be a related species.

Also, you can cut open the gall and look for the bug in the middle, which could also be helpful. ;D

Galls are weird.

SwampDonkey · December 09, 2013, 07:46:04 PM

I'd say a gall. But depending on what type of bud, the midge or wasp or whatever insect hits, the shape of the gall can be different. For instance that could have been a bud containing male pollen flowers. A regular bud might look like a spiky ball. And the insect may be particular as to what bud type it hits. We have a spruce gall that hits regular buds on branch tips, but they look cone like. The position in the canopy is not high enough to be in seed cone buds. Spruce gall midge is the bug in this example. This is a way for the insect to make a kind of nest and all she had to do is inject the bud and let the tree grow the nest for her. Why not make the host do all the work. Sounds like some visiting relatives. :D

WDH · December 09, 2013, 09:21:07 PM

I also suspect that it is insect related, most likely some sort of gall. The good news if that is true is that they are relatively harmless.

thecfarm · December 09, 2013, 09:39:28 PM

That is odd.
Thought you might want to see how mine grow.

An old thread about it.
https://forestryforum.com/board/index.php/topic,65593.msg979675.html#msg979675

sim0n · December 10, 2013, 11:59:05 AM

I dissected a couple of more and found white larva in some of them. As well as a bunch of small spiders.

It just occurred to me that one year there were a lot of brown golfball-like galls on these same group of oaks. Possibly related or a different insect?

In any case I'm glad to know they're harmless