# Tree Leaf Warts **URL:** \ **Category:** Factual Questions\ **Created:** [June 12, 2003, 10:49pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465 "2003-06-12T22:49:27Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [June 12, 2003, 10:49pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/1 "2003-06-12T22:49:27Z")
On my walk today, I noticed that the leaves and smaller branches of many of the trees around have little nodules all over them, about a quarter inch wide. They’re randomly scattered and don’t look like a natural feature of the tree. I’m guessing that it’s either caused by a virus or some kind of parasitic insect larva, although since this is New Jersey I can’t rule out tree-cancer from all the pollution. Anyone know what these might be? ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [June 12, 2003, 10:52pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/2 "2003-06-12T22:52:40Z")
They’re insect eggs. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [June 12, 2003, 11:02pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/3 "2003-06-12T23:02:52Z")
The lumps themselves aren’t insect eggs, as they’re woody material grown out of the tree, unless you mean that an insect embeds an egg in the tree and the tree grows a lump around it in response. That would make sense. Anyone know what kind of insects around here are responsible? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 12, 2003, 11:06pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/4 "2003-06-12T23:06:36Z")
Probably gall wasps of some kind. What kind of trees are they on? ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [June 12, 2003, 11:14pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/5 "2003-06-12T23:14:27Z")
Actually Mangetout, I remebr doing a biology project at school about this and IIRC (it was few years ago) the gall wasps are parasites of the actual eggs in the leaves. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 12, 2003, 11:24pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/6 "2003-06-12T23:24:28Z")
Hmmm, are you sure that is _generally_ the case? - I know many wasps are parasitic of (other)insect larvae/eggs (particularly some Chalcid wasps, IIRC), but many species parasitise plants directly, I believe… From [here](http://www.everythingabout.net/articles/biology/animals/arthropods/insects/wasps/gall_wasp/) > [@](#): > > Most species of gall wasps attack specific tissues of the host plant, forming galls, a type of defense response, on roots, stems, twigs, leaves, buds, or flowers. Salivary secretions from the wasp larva stimulate the plant to produce the gall, so the insect actually modifies the plant’s normal response to injury, resulting in food and shelter for the larva. Many leaf galls are red and white and resemble miniature stars, sea urchins, cones, cups, or saucers ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [June 12, 2003, 11:26pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/7 "2003-06-12T23:26:27Z")
> [@](#): > > \*Originally posted by Mangetout \* > \*\*What kind of trees are they on? \*\* Not sure. Possibly some kind of small maple, I’ll take a closer look tomorrow. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [June 12, 2003, 11:28pm UTC](https://boards.straightdope.com/t/tree-leaf-warts/181465/8 "2003-06-12T23:28:38Z")
Yes, you’re right then Mangetut, I was thinking of different sort of wasp and a different sort of tree parasite.