Ficus gall wasp—Josephiella microcarpae
This tiny wasp (family Agaonidae) infests only Indian laurel fig, Ficus microcarpa.
Presence of this pest is recognized by the spherical swellings or warty blisters that develop on the lower and upper surfaces of Indian laurel fig. Each gall is about 1/20 to 2/3 inch in diameter. Except for the adult, all life stages occur only within host tissue.
Adults are 1/10 inch long, dark brown wasps with pale brown or orange antennae and legs and clear wings. The pale, legless larvae that feed in galls grow up to about 1/10 inch long.
Note several other insects also cause galls on ficus. These inadvertently introduced pests and their host plants are native to Southeast Asia.
Cuban laurel thrips, Gynaikothrips ficorum, and weeping fig thrips, G. uzeli. These look-alike thrips cause leaves of Indian laurel fig and weeping fig, respectively, to fold along the midvein and form a permanent gall. Gynaikothrips also cause dark brown, reddish, or purplish scarring on galled foliage, unlike the leaf swellings of ficus gall wasp that mostly remain green.
Ficus eye-spot midge. Horidiplosis ficifolii causes elliptical to irregularly shaped blisters or swellings in leaves of Indian laurel fig. Each swelling is up to about 1/5 inch long. The swellings later turn brown and sunken with a tiny hole where the mature midge larva emerged. Weeping fig is not infested by this gall midge even when growing near heavily infested Indian laurel fig.
Ficus leaf-rolling psyllid. Trioza brevigenae is an aphidlike insect that causes Indian laurel fig leaves to become tightly rolled lengthwise into narrow, pencil-like cylinders about 1/6 inch in diameter. These cylinders may harbor various nymphal stages of the psyllid. Infested leaves become dry and brittle but remain uniformly green.
Gall wasps develop through four life stages: egg, larva, pupa, and adult. The adult female lays eggs in leaf tissue of Indian laurel fig. The hatching larvae feed and grow inside the leaf, causing a swelling. After pupating, when adults emerge they leave tiny holes in galls on the underside of leaves.
Larvae feed inside young terminals, causing expanding leaves to develop spherical swellings. Infested leaves may curl, turn yellow, and drop prematurely. Because young leaves are especially susceptible to galling, damage can be most extensive on the new growth stimulated by recent pruning, such as on frequently pruned Indian laurel fig used as topiary plants.
Although infestations are aesthetically undesirable, tree health and survival appear not to be threatened by the leaf galls. No control action is necessary to protect plant health and survival.
Avoid this damage by planting other Ficus species. Alternatives include creeping fig (F. pumila), Moreton Bay fig (F. macrophylla), and rubber plant (F. elastica).
Pruning, bagging, and disposing of young infested leaves helps reduce local gall wasp populations, but pruning can stimulate excess succulent new growth that attracts the egg laying female wasps. Promptly raking and disposing of fallen leaves may help reduce subsequent infestations by removing some pupae before the wasps emerge as adults.
Where damage is intolerable, applying a systemic insecticide (e.g., acephate, dinotefuran, imidacloprid) can help to reduce future damage. Because these broad-spectrum, persistent insecticides move into pollen and nectar on which adult natural enemies and pollinating insects feed, if used apply them shortly after the end of flowering to reduce subsequent galling.
For more information see A New Species of Josephiella (Hymenoptera: Agaonidae) Forming Leaf Galls on Ficus microcarpa L. (Moraceae) (PDF).
Adapted from the publication above and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).