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What are the funny little balls growing on your live oak tree? Or the fuzzy little asps on the underside of your oak tree’s leaves? And are they dangerous?

They’re insect galls, which look bad but are relatively harmless. They’re produced when a beneficial wasp lays eggs, and the tree, in a defensive move, creates the wood or fuzz around them.

In some parts of the world, other insects like mites create galls, but in this neck of the woods, it’s almost always wasps on hardwood trees like oaks, elms and cypress trees.

While they may be unsightly, they will never kill a tree. And in most cases, insect galls usually cycle off the tree in less than a year. They’re most commonly seen on smaller stems and on the undersides of leaves, but they may also show up on flowers, fruits, trunks and roots.

If you want to prevent them, you have to spray the tree with a residual insecticide every 30 days, usually from early May through early July. This will deter wasps from laying eggs.

The ultimate control, however, is a healthy tree — the weaker the wood, the easier it is for wasps to lay eggs.