What Causes This Leaf To Have This Strange Protrusions On The Bottom.

Question

I found this leaf in my yard. And I am worried about my grape vine.

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Answer 1

Those are insect galls. You can prevent them with insecticides. Here is an article that will help:

https://www.gardeningknowhow.com/plant-problems/environmental/treating-leaf-gall-on-plants.htm