Answer: What you describe are called oak tree galls and are made by a wasp. Generally, insecticidal control is not satisfactory because the wasps are physically protected within the galls. As a rule, the galls are unsightly but will not harm your tree. Where practical, pruning of infested twigs may help to reduce the problem on lightly-infested trees. However, pruning is impractical if large trees are heavily infested. A commercial arborist may be able to provide assistance with valuable plantings.
Q&A Library Searching Tips