These abnormal growths are called galls. The insect that causes galls in pecans is phylloxera, which are tiny, soft-bodied insects closely related to aphids. The two most important insect species attacking pecans are the pecan leaf phylloxera and pecan phylloxera. The pecan phylloxera is the most-damaging species because it attacks the shoots and nuts. The pecan leaf phylloxera forms galls on the leaves only. Phylloxera survive the winter as eggs in bark crevices. In the spring, the tiny nymphs emerge during budbreak and feed on new growth. A substance is secreted while feeding that stimulates plant tissue to develop abnormally, thus creating galls. Young phylloxera are enclosed in the galls and feed inside them until the galls crack open and the adults emerge to lay eggs. Galls on leaves are not usually harmful, although heavy infestations may cause some defoliation of trees. Phylloxera cannot fly far and infestations move slowly from tree to tree. If treatment is warranted, mark the trees with gall infestations for treatment the following spring. Insecticides for phylloxera must be applied after egg hatch in the spring but before nymphs are protected in galls. Specific insecticides should be chosen in consultation with your local Cooperative Extension Office.

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