These spores are spread by the wind and splashing rain to the bark or buds of other camellias where they’ll lie dormant until next year and cause infection next spring. As these galls mature, several layers of the lower leaf surface will peel away revealing a white color, which is the spores of the fungus. Two common species of twig gall-producing insects are the horned oak gall wasp, Callirhytis cornigera , and the gouty oak gall wasp, C. quercuspunctata . Erineum galls are caused by several species of eriophyid mites in the genus Eriophyes. Gall midges (Cecidomyiidae) are a large group of small (usually less than 1/4 inch long), delicate flies that cause bud galls, blister galls, and galls on leaves and other plant tissues. Leaves of hackberry trees often have the hackberry nipple gall, caused by an … Most leaf galls on oak cause little or no harm to the health of a tree. However, twig or branch galls may cause injury or even death to a heavily infested tree. Galls are abnormal swellings of plant tissue, usually on leaves and stems. These are caused by a very small wasp. Most insect and mite galls are caused by chemicals produced by the egg laying and feeding activities. This gall is caused by an aphid that passes the winter in eggs laid on twigs of the plant. The maple spindle gall mite, V. aceriscrumena, causes galls to form on the upper surface of sugar maple, A. saccharum foliage. Feeding by the aphid causes the formation of conical galls on the upper side of the leaf. Each gall, produced by single aphid, later becomes filled with offspring. The abnormal growths developing in oak tissue are due to the powerful enzymes given off by the immature gall-forming insect as it grows. They grow to the size of a golf ball and have an interesting life cycle. For example, gall midges cause leaf spot galls, which are characterized by noticeable leaf discoloration (Figure 10), and vein pocket galls … The resulting larvae cause oblong blister-like galls to develop on the leaves. For example, the oak-apple gall appears as fairly large, round, apple-like growths. The chemicals cause the affected plant cells to swell. This gall on an oak leaf (Quercus) looks like an oak flake gall caused by a wasp (Hymenoptera) but dissecting the gall is the only sure way to tell what caused the gall Galls are abnormal growths that occur on leaves, twigs, or branches. The adults emerge from the gall in early summer and lay eggs on the leaves of the tree. A sunken scar marks the spot of the gall. In general, most gall wasps on oak trees don’t affect the trees' health. The gall in this tree is a Horned Oak Gall. Some may affect twigs, such as the gouty oak gall, and actually cause some dieback. The gall wasp, Andricus quercuslanigera, causes a woolly gall on the midrib of the leaves of live oak.Oaks in general have a flourishing fauna of gall wasps associated with them. Neuroterus irregularis causes an irregular gall on the leaves of post oak. If enough galls form on a leaf, the leaf may die back. Neuroterus saltarius forms tiny galls on the leaves of post oak that are dehiscent, that is, they drop off of the leaf. These eriophyid mite-caused galls … Mature aphids with wings leave the galls in late spring and early summer and fly to … Galls may drop from leaves, leaving only the damaged foliage. They may be caused by insects, mites, bacteria, fungi, or nematodes. One Extension agent … Most leaf galls on oak are not damaging. These galls are small, elongate, projecting growths that give the leaf a spiked appearance. This typically causes the leaves to appear scorched. General, most gall wasps on oak cause little or no harm to the size of a ball. 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