How to Manage Pests
UC Pest Management Guidelines
Avocado Brown Mite
Scientific name: Oligonychus punicae
(Reviewed 1/07, updated 1/07, pesticides updated 5/15)
In this Guideline:
Spider mites (family Tetranychidae) and predatory mites (Phytoseiidae) are tiny 8-legged arthropods. Persea mite is a key pest of California-grown avocados. Avocado brown mite and sixspotted mite are sporadic pests. Several beneficial mites are important predators of pest mites and certain insects. Natural enemies and certain management strategies vary among pest mites. Identify the pest and natural enemy species in your grove and learn their biology so you can manage these pests appropriately as needed. For details about sampling techniques, see MONITORING PERSEA AND SIXSPOTTED MITES.
Avocado brown mite (family Tetranychidae) is dark brown, oval, and tiny (about 0.01 inch or 0.3 mm long). Its tiny amber-colored eggs have a short projecting stalk. At low populations most eggs are laid singly along the midrib. Eggs are increasingly found throughout the upper leaf surface as populations increase. In summer there may be two complete generations per month. Temperatures of 90° to 95°F or higher usually kill these mites and their eggs, as does the first cold weather in fall or early winter.
Avocado brown mite is a sporadic pest, mostly in coastal growing areas. Bronzing of leaves, mite cast skins, and partial defoliation of some trees by avocado brown mite is most noticeable from about July to September. Severe infestations tend to occur in border row trees along dirt roads, where road dust is detrimental to mite predators. Ash deposited on leaves from wildfires reportedly also causes brown mite outbreaks.
Avocado brown mite feeds almost entirely on upper leaf surfaces. It causes no significant damage when population densities are low to moderate (about 10 to 20 adult females per leaf). If the spider mite destroyer lady beetle (Stethorus picipes) is present and reproducing well at this time, brown mite does not become a problem. Damage occurs if avocado brown mite averages about 50 to 70 adult females per leaf (about 100-200 motile stages, adults and nymphs combined). At these higher densities mites also colonize the lower leaf surface and sometimes fruit, and partial defoliation can occur. These higher populations cause leaf bronzing along the midrib, then along smaller veins, and finally the entire leaf turns brown.
Natural enemies and temperature (hot or cold weather) usually maintain this mite at innocuous levels. Maintain good biological control by conserving natural enemies. Control dust and avoid applying broad-spectrum pesticides for any pests. When treating any pests, including avocado brown mite during late summer or fall, spot treat individual trees where possible.
Organically Acceptable Methods
Monitoring and Treatment Decisions
UC IPM Pest Management Guidelines:
B. A. Faber, UC Cooperative Extension, Santa Barbara/Ventura counties
Acknowledgment for contributions to Invertebrates:P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
M. Blua, Entomology, UC Riverside
P. Oevering, UC Cooperative Extension, Ventura County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
T. Roberts, Integrated Consulting Entomology, Ventura, CA
B. B. Westerdahl, Nematology, UC Davis