If you have an oak tree in your home landscape, you might have spotted small, unsightly brown balls hanging like fruit or growing into a branch. These little balls, called oak galls, are a common occurrence caused when the tree reacts to non-stinging wasps laying their eggs on its leaves, branches, twigs or flowers. These insects inject a hormone into the plant tissue, causing it to grow abnormally and enclose the developing wasp larvae. Galls usually don't cause lasting harm, but heavy infestations can be fatal. Fortunately, you can get rid of oak galls in a few simple steps.
1Identify oak galls on your trees. These growths typically emerge at bud break in the early spring. A developing gall typically looks like either a big seedpod or a small, tumor-like growth on the leaves, branches or stems.
2Look for symptoms of gall. Affected oak tree leaves often appear scorched, blackened or curled and fall prematurely. Horned and gouty oak galls sometimes create solid masses that might girdle entire branches.
3Prune out gall-infected branches and twigs with a small saw or pruning shears. Burn or step on the galls promptly to kill the developing larvae. Place gall remains in a tightly sealed baggie or trash bag and discard immediately.
4Prevent the spread of this oak tree disease by promptly raking up fallen leaves and twigs. Gall-producing insects often overwinter in the debris.
5Reduce the gall-producing insect population by hanging bird feeders from your oak trees. Your feathered friends are natural predators of the various gall wasps.
6Spray an application of carbaryl when the buds break in the spring. This stops the adult females from laying eggs and helps reduce leaf gall formation. Follow the instructions on the product's label.