It is most commonly found on silver maple trees. The small, white, popcorn-like objects are likely cottony maple scale. There are small, white objects resembling kernels of popcorn on the branches of my silver maple tree. In most cases, controlling tar spot with a fungicide is not practical or feasible. The severity of tar spot can be reduced by raking and removing infected leaves from around the base of the maple tree in fall. Fortunately, tar spot does not cause serious harm to maple trees. Several fungi in the genus Rhytisma cause tar spot. Tar spot is a common leaf spot on maples in the United States. There are black spots on my maple leaves. Preventive insecticide treatments are seldom warranted. Galls cannot be “cured” once they have formed. While galls may be unsightly, they do not cause serious harm to healthy, well-established trees. Other galls that are commonly seen on maple leaves include the maple bladder gall (small, globular, wart-like, red or black growths on upper leaf surfaces), gouty vein gall (thickened, green or red, pouch-like swellings along leaf veins on lower leaf surfaces), and velvet or erineum galls (green to red, velvet-like patches on the undersides of leaves). Adult mites leave the foliage in the fall and move to overwintering sites. Mite activity continues until mid-summer when it starts to decline. Only new leaves are capable of producing galls. Reproduction is prolific and as the new mites mature, they leave the gall and move to other newly emerging leaves to repeat the process. The gall encloses the mite, which continues to feed and lay numerous eggs within the gall. The leaf responds to the small irritation by rapidly producing extra cells that form the abnormal growth at the feeding site. In early spring, the adults move to developing, unfolding leaves and begin feeding. Adult mites spend the winter under the bark and other protective places on the trees. Maple spindle galls are caused by extremely small mites that are only 1/125-inch long. The galls are somewhat thicker in the middle than at the ends, hence the common name of spindle gall. They are as thick as the lead in a pencil. Maple spindle galls are yellowish green and about 1/5-inch long. The hair-like gall on the maple leaves is probably the maple spindle gall. Galls are abnormal growths of plant tissue induced to form by mites, insects or other small organisms. The leaves on my maple tree have erect, spike-like growths on their upper leaf surfaces. Horticulturists from Iowa State University Extension and Outreach answer questions about galls, fungi and scale that may appear on maples. AMES, Iowa – As homeowners enjoy the shade from their maple trees, they may notice something strange on the leaves or branches.
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