For the past couple weeks, the UGA Cherokee County Extension Office has been inundated with questions on the oaks in our area. Leaves appear to have multiple gray-brown spots that in some cases cover the entire leaf. This is not a disease. This damage from the solitary oak miner-a tiny caterpillar, which affects mostly white oak species. While the damage looks severe it largely an aesthetic problem with minimal health consequence to the tree. No treatment is needed.

The leaf miner can infest burr oak, eastern black oak, and red oak, but prefer white oaks This species of leaf miner can have multiple generations per year and over winters in leaf litter. Leaf disposal and destruction is effective in reducing their numbers but would need to happen across the immediate area to have an impact.

According to a NC State University Fact Sheet, “Solitary oak leaf miners, Cameraria hamadryadella, are tiny caterpillars that feed between the outer layers of oak leaves. They are small, flat, taper toward the rear and are shaped somewhat like the rattles of a rattle snake. Mature larvae are about 1/4 inch long. As solitary oak leaf miners feed, they form irregular, blotch-like mines. As their name implies, only one leaf miner occurs in each mine. Mature leaf miners spin a flimsy, white, oval cocoon within the leaf and pupate within it. Solitary oak leaf miner pupae are slender, brown, and taper toward each end.

Pupae wriggle to the surface of the mine and new adults emerge that are pale, silvery moths with bronze blotches on the wings. These moths are so small they are termed “microlepidoptera.” This insect overwinters as diapausing larvae in fallen leaves. A new generation of tiny moths emerges during the spring. After mating, females cement eggs one at a time to the upper surface of leaves.

In addition to the oak leaf miner there are other insects that will cause leaf deformities on oak leaves. The UGA Extension Center for Urban Agriculture website writes that “oak leaf galls are abnormal vegetative growths on trees that result from the feeding and egg laying activities of various insects and mites. Chemical secretions from the adults while laying eggs as well as the saliva from the feeding larvae cause the plant to react abnormally.”

“The more common gall producers on trees are aphids, beetles, jumping plant lice, midges, mites and wasps. Each species causes a swelling of plant tissue that is characteristic on specific plant parts such as the stem, twig, leaf or petiole. Most often the gall is more readily identified than the gall producer. It is convenient to identify galls and their producers simply by noting where the gall is located and also the shape of the gall. Table 2 on page 43 of the Forest Health Guide for Georgia from the Georgia Forestry Commission lists some of the more common trees that are frequently attacked by gall producers along with a description and location of the gall.

Generally, galls are not life threatening to trees. Oftentimes the most drastic effects are premature leaf fall and dieback of several smaller branches. On small trees, galls should be pruned and destroyed. Leaf and twig litter that is on the ground around the base of the tree should be raked and disposed of. A few of the common species are shown in the images included here.

Joshua Fuder, Agriculture and Natural Resources Agent, UGA Cherokee County Extension office. If you have any questions, call 770-721-7830 or visit my blog @ blog.extension.uga.edu/cherokee. For upcoming seminars, follow us on Facebook at www.facebook.com/ cherokeemastergardeners or on our website at cherokeemastergardeners.com.

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