How to Manage Pests
UC Pest Management Guidelines
Scientific name: Eotetranychus sexmaculatus
(Reviewed 1/07, updated 8/08, 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.
The oval adults are about 0.01 inch (0.3 mm) long. Their body is lemon yellow, often with about six dark blotches on the abdomen, although some individuals have no distinct spots. Females lay tiny, globular, pale greenish yellow to translucent or pearly white eggs, which have a slender projecting stalk. About 25 to 40 eggs are laid over 10 to 20 days. Eggs hatch in 5 days to 3 weeks, depending on temperature. In summer, mites reach maturity in 8 to 12 days. Populations are heaviest in spring and early summer.
Sixspotted mite is an occasional pest, mostly near the coast in foggy areas of San Luis Obispo and Santa Barbara counties. It generally is under good control in the interior growing areas (Riverside and San Diego counties) because of predators and warm weather. Sixspotted mite can become a problem anywhere if trees are drought-stressed or pesticides used to control other pests disrupt mite biological control.
Sixspotted mite feeds only on the lower avocado leaf surface. It causes irregular brown to purplish discoloring, mostly along the midrib and larger veins. Sixspotted mite produces webbing, but not the dense roundish silk patches formed by persea mite.
Enhance biological control by conserving natural enemies. Minimize dust. Avoid applying non-selective pesticides that are toxic to predaceous insects and beneficial mites that control plant-feeding mites and other pest insects. Limit any needed applications to spots where pests are most abundant.
Organically Acceptable Methods
Monitoring and Treatment Decisions
Sixspotted spider mite can severely stress trees at relatively low densities by causing premature leaf drop. However, populations rarely exceed an average of 2 to 3 mites per leaf. At this low abundance sixspotted mite is not damaging, does not warrant treatment, and is easily overlooked.
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