Bug eggs on Oak leaves
Location: Southeastern Iowa
August 16, 2010 2:35 pm
The attached photos show a multitude of bug eggs on the leaves of the oak tree in my backyard.
I cannot identify what bug these eggs are associated with. I would like to know if there is any danger to the tree’s health or to my home from these bugs.
Hi Jay D,
This is not an egg. It is a Gall. A Gall is a growth on a plant caused by an wasp, midge, mite, or occasionally another type of insect. According to BugGuide: “There are more than 2,000 gall-producing insects in the United States; 1,500 are either gall gnats or gall wasps.” The insect produces an enzyme that causes the plant tissue to grow in a deformed manner, and this growth serves as food for the developing gall larvae. It is generally believed that the Gall does not harm the plant. We believe your Gall is a Gall Wasp in the family Cynipidae, but we could not find a conclusive match on BugGuide. There is one image of an unidentified Gall Wasp Gall on BugGuide that looks similar to your Gall. BugGuide gives this advice for Gall identification: “Gall insects (and mites) are usually highly specific about what kind of plants they use, and even what part of the plant. To maximize your chances of getting a gall identified, record the plant species (include photos of the leaves, flowers, fruits, etc. if you’re not sure), and if it’s a leaf gall, note the position on the leaf (if it’s not obvious from the photo): upper side or underside; midrib, side vein, or somewhere else. Also note whether or not the gall is detachable, the size of the gall, and anything else distinctive about it that may not be clear in the photo. With oaks in particular, which are hosts for hundreds of kinds of galls, every little detail can help to narrow down the options.” An interesting side note is that Alfred Kinsey who shot to notoriety in the mid twentieth century with his ground breaking studies on human sexuality began his professional career as an entomologist who specialized in the study of Gall Wasps. He approached his studies on human sexuality with the same rigor that he used in collection over 1 million specimens of Gall Wasps.