Galls

These festive ornaments are actually leaf galls! Galls are unusual plant growths that are caused by certain insects, mites, fungi, bacteria or viruses. These fallen leaves of Texas live oak (𝘘𝘶𝘦𝘳𝘤𝘶𝘴 𝘧𝘶𝘴𝘪𝘧𝘰𝘳𝘮𝘪𝘴) have galls caused by two different types of wasp (gall wasps don’t sting people). The fluffy balls are caused by the woolly gall wasp (𝘈𝘯𝘥𝘳𝘪𝘤𝘶𝘴 𝘲𝘶𝘦𝘳𝘤𝘶𝘴𝘭𝘢𝘯𝘪𝘨𝘦𝘳𝘢), which tends to settle along the midrib of the leaf. The colorful beads are caused by another gall wasp, probably a 𝘉𝘦𝘭𝘰𝘯𝘰𝘤𝘯𝘦𝘮𝘢 species. The larvae of these wasps secrete chemicals that increase plant growth hormones, which triggers the plant to produce galls. The larvae then live and feed in the gall tissue. Galls are a pretty normal part of being a tree, and a healthy oak tree can easily host a fair few gall tenants without lasting harm. Most people think galls are freaky but I think many of them are pretty cool!