Though Aceria hibisci can feed on a wide variety of hibiscus plants, it seems to demonstrate a preference for the Chinese red hibiscus (Hibiscus rosasinensis L.)
By Damon Adamson.
Often going unnoticed until the telltale bump-like clusters form on hibiscus leaves, the Hibiscus Leaf-Crumbling Mite or Aceria hibisci, is small enough to escape most human visibility. The unsightly growth or galls are the results of feeding Aceria hibisci, otherwise known in Hawai’i as the Hibiscus Erineum Mite or just the Hibiscus Mite.
First identified in Hawai’i in 1989 on the island of Oahu. Now the microscopic mite can be found on most of the Hawaiian islands and other Pacific areas, like Fiji, the Cook Islands, New South Wales, Australia in 1992, and Brazil.
The adult Hibiscus Erineum mite is very small—invisible to the unaided eye. The mite is soft-bodied and wormlike, with two body regions: the gnathosoma (mouthparts), and the idiosoma (remainder of the body). Hibiscus Erineum mites are unique among mites because they have only two pairs of legs, compared with the four pairs of other mite species. Aceria hibisci are about 0.2 mm long and are voracious vascular plant feeders.
Interestingly, though Aceria hibisci can feed on a wide variety of hibiscus plants, it seems to demonstrate a preference for the Chinese red hibiscus (Hibiscus rosasinensis L.). Infrequently the mite has been seen feeding on plants of the same family, but are generally limited to the Hibiscus family.
Their feeding is directly responsible for the unattractive, often-clustered and gnarled-looking, puckered bumps that affect leaves, buds and flowers, small limbs and twigs, but especially new vegetative growth (Photo 1). Often, other mites and plant insects can been seen within and surrounding the gall damaged areas. These may or may not be pests. There exists many mites and other bugs that can feed on the Aceria hibisci. A rule of thumb suggests that if you see quick-darting very small insects, they are potentially predatory and are seeking other pests.
Biological control consists of a broadened understanding of microscopic pests and predators. Predatory mites within the family of Phytoseiidae have been identified as having an association with the galls and it appears that when they are present, there is lessened galling over time. Chemical control methods are present, however when miticides are applied, it not only targets the Hibiscus Erineum Mite, but the helpful predatory types as well.
Damon Adamson (senior, horticulture) received a bachelor of arts in history from UH West O‘ahu. He is retired U.S. Army, born in San Diego, CA.