oak apple

plant tissue swelling

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July 1, 2026

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An oak apple is a large, round gall that forms on oak leaves and twigs. These galls are plant tissue swellings caused by the larvae of gall wasps.12

Gall wasps (family Cynipidae) are small insects that stimulate the growth of galls on plants. Many species of gall wasps attack oak trees. The oak apple gall, specifically, is produced by gall wasps like Amphibolips confluenta or Biorhiza pallida. These galls can be quite large, with some reaching 1 to 2 inches in diameter and potentially containing numerous larvae. The larvae feed on the plant tissue within the gall as they grow and develop.21

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gall wasp
Major species
The so-called oak apple, a round, spongy, fruitlike object about 2.5 to 5 cm (1 to 2 inches) in diameter, is caused by the larvae of the gall wasp Biorhiza pallida. About 30 such larvae may develop in a single “apple,” or gall.
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The so-called oak apple, a round, spongy, fruitlike object about 2.5 to 5 cm (1 to 2 inches) in diameter, is caused by the larvae of the gall wasp Biorhiza pallida. About 30 such larvae may develop in a single “apple,” or gall.
Read More