NC State Extension Publications

Description and Biology

Skip to Description and Biology

The privet rust mite, Aculus ligustri, is a microscopic mite with teeny-weeny, scissor-like mouthparts that it uses to puncture the epidermis of the leaves of ligustrum to feed. As privet bud mites feed, they inject their saliva possibly to help lubricate the mouthparts or possibly to predigest the tissue they are feeding on. Privet rust mites become active shortly after the leaves begin to develop in spring. The mites multiply rapidly on the leaves and green stems. Hot weather has a deleterious effect on the mite population perhaps because it favors the development of a parasitic fungus, Hirsutella thompsonii. Predaceous mites and insects are also more abundant in hot weather. Consequently in hot, humid weather, privet rust mite populations may drop to almost undetectable levels. During the warm summer period, these mites survive as aestivating females under old bud scales at the base of the current season's growth. With the advent of cool fall weather, the mite population begins to build up again. The typical life cycle of eriophyid mites includes an egg, two nymphal instars, and an adult stage. These mites can develop from eggs to adults in one week under favorable conditions. They can be distributed to other privets by wind, insects, and birds.

Rust mites are microscopic, cigar-shaped, and have four legs.

Rust mites are microscopic, cigar-shaped, and have four legs.

Privet rust mites cause distorted leaves and eventual defoliatio

Privet rust mites cause distorted leaves and eventual defoliation.

Privet rust mites on a distorted Chinese privet leaf.

Privet rust mites on a distorted Chinese privet leaf.

Privet rust mites on Chinese privet stem.

Privet rust mites on Chinese privet stem.

Privet rust mite on a privet bud perhaps seeking an aestivation

Privet rust mite on a privet bud perhaps seeking an aestivation site.

An eriophyid mite infected with Hirsutella thompsonii fungus.

An eriophyid mite infected with Hirsutella thompsonii fungus.

Host Plants

Skip to Host Plants

Eriophyid mites tend to be very limited in the plants they can infest. Privet rust mite infests Chinese and other privets. Their saliva has powerful enzymes that act as plant growth regulators on young leaves, causing leaves to become distorted as they enlarge. On older leaves, the damage is apparent as minute pale flecks or stipples, which, when abundant, give the overall shrub a grayish cast. Heavy populations of privet bud mites may cause premature defoliation.

Residential Recommendation

Skip to Residential Recommendation

Fortunately, privet rust mites are susceptible to the pesticides Sevin and Orthene. Sevin is readily available and not particularly toxic to humans and pets.

References

Skip to References

For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: Nov. 5, 2013
Revised: Oct. 11, 2019

N.C. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status.