Ficus Eye-Spot Midge Introduced in Southern California

This exotic pest (Horidiplosis ficifolii) from Southeast Asia was inadvertently introduced into southern California in about 2014. The gall midge (family Cecidomyiidae) mines and galls foliage of Indian laurel fig (Ficus microcarpa).

Identification

Elliptical to irregularly shaped blisters or swellings in fig leaves, each up to about 1/5 inch long, are caused by the gall midge larvae feeding in leaf tissue. The green swellings later turn brown and sunken.

If you place damaged leaves with green swellings in a clear plastic bag, within a few days the orange larvae will emerge if the leaves contained ficus eye-spot midge. Cutting open a green swelling before it darkens can reveal a maggotlike larva inside. Young larvae are translucent and less than 1/25 inch long. As they feed, larvae turn green then bright orange and grow up to 1/12 inch long. After a mature larva exits its mine to pupate, a tiny, circular hole is left in each brown, sunken blotch.

Adults are delicate, orangish, slender flies with long antennae and legs. They are about 1/12 inch long without any markings on the wings.

Life cycle

Gall midges develop through four life stages: egg, larva, pupa, and adult. Adult females lay eggs on young leaves of Indian laurel fig. The hatching larvae chew into the leaf and feed inside, causing a greenish gall or swelling to develop where each larva feeds individually. Mature larvae exit their gall and drop to pupate in organic litter and topsoil.

Egg to development of the adult (1 generation) is completed in about 1 month when temperatures average 68ºF. There are multiple generations per year.

Damage

Larvae mine and create galls on the foliage of Indian laurel fig. Weeping fig, Ficus benjamina, is not infested even when growing near heavily infested Indian laurel fig.

Larval feeding causes formation of blisterlike swellings (galls) in leaves. Galls are elliptical to irregularly shaped and up to 1/5 inch in diameter. When a larva exits its gall to pupate, the swelling collapses and turns into a brown, sunken blotch that could be mistaken for a bacterial or fungal leaf spot disease. Heavily infested leaves may drop prematurely. Although unsightly, this aesthetic damage apparently does not threaten plant health or survival.

Solutions

No specific management is known except to remove and dispose of infested leaves before the larvae emerge. If you find a suspected infestation of ficus eye-spot midge where this pest is not known to occur, please report this to the local county agricultural commissioner or UC ANR Cooperative Extension office. For more information and photographs see New Invasive Pest, the Ficus Eye-spot Midge, Horidiplosis ficifolii in California and New Pests of Landscape Ficus in California (PDF).

Adapted from the publications above and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).