They look like cotton. Is the gall specific to a tree species or to an insect? What's That Fuzzy Stuff on My Tree? Every year about this time I receive a number of calls from homeowners who have oak trees about a fuzzy ball growing on the leaf of their trees. What could they be? Several others are on the ground, blown down by wind. This thread reminded me to look it up. More noticeable when the wind blows. Q.I have fuzzy light brown cotton balls on the underside of the leaves on my oak tree. Two weeks earlier had come a question from East Bethel in Anoka County: “I have an oak tree that has fuzzy growths on the leaves. The oak tree looks perfectly healthy, and has been dropping a few occasional balls for 2 years. These larvae cause the oak tree to manufacture cells and substances that produce the gall and in turn the wasp larvae use the gall as both food and shelter. It is a fluffy mass of around 20-30 mm in diameter which, as the name suggests, resembles a ball of cotton-wool in appearance and texture. Oak galls come in many sizes, shapes and colors but are all products of the oak trees' reaction to the larvae of certain wasps known as gall wasps. Cottonwood trees are common in North America, Europe, and some parts of Asia. I see these fuzzy balls dropping from my neighbor’s oak tree this year; some are also still attached to dropped leaves. They look like cotton. Galls are irregular plant growths which are stimulated by the reaction between plant hormones and powerful growth regulating chemicals produced by some insects or mites. Hi, I have an oak tree that has fuzzy growths on the leaves. Shawn says: September 27, 2015 at 5:09 pm. Like Like. Looking at a woolly aphid colony from above, you see tiny black dots amongst the fuzzy, white, cottony substance. Upon closer examination, I see they appear to be cotton balls. Peter L. Warren Facebook Just as an oak tree's buds break open in February or March, an adult wasp would alight on a juicy, fast-growing leaf to lay eggs. Internet says : " The highly distinctive cotton-wool gall develops on the male catkins of oak trees. I live in central MD, by the way. Cottonwood trees are huge deciduous trees that have large green leaves and thick foliage. I thought they were galls but I just see a little seed like thing inside. If not, you might be surprised to see clusters of fuzzy yellow-beige balls on the underside of some of those leaves. They tear apart much like a cigarette filter and are filled with hard seeds. They appear to have been opened by either birds or squirrels that were looking for food. They look like cotton. Reply. They aren't oak galls, because I looked it up on the internet. Oak trees can produce galls — fuzzy red growths that look like cotton balls — when they’re invaded by fungi, insects or mites. Have you looked up at your live oak leaves recently? One of the common features of all types of cottonwood trees is the fluffy cotton-like strands that appear every June. Uh oh! If they are galls can you give me a little more information such as what insect, how long do the take to mature? This is the first time I have seen these here in 35 years. Saw these on my deck this morning, below an oak tree. These are leaf galls. From a distance, a woolly aphid colony can appear to be a fuzz or moldy growth on a tree branch.