Howardian Local Nature Reserve Close Window ~ Oak Apple Biorhiza pallida ~ May Oak apples are caused by chemicals injected by the larva of Biorhiza pallida which has 2 generations in its life cycle. One being sexual and the other is agamic (females who can reproduce without mating). The adult female wasp lays single eggs in developing leaf buds. The larvae feed on the gall tissue resulting from their secretions. Howardian Local Nature Reserve Back to top