How to Manage Pests
UC Pest Management Guidelines
Scientific name: Eotetranychus sexmaculatus
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.
Sixspotted mite is controlled primarily by predatory
mites (family Phytoseiidae). These phytoseiids include Amblyseius(=Typhlodromalus) limonicus and Galendromus helveolus. Euseius hibisci, a shiny pear-shaped predator, is important in part
because it can maintain and increase its populations on avocado pollen when
pest mites are scarce. Typhlodromus rickeri also preys on sixspotted mite around Santa Barbara
County. The spider mite destroyer lady beetle (Stethorus picipes) and sixspotted thrips (Scolothrips
sexmaculatus) are other important natural enemies.
Encourage predators by oiling or paving main orchard
roads to control road dust. Drive slowly when it is necessary to use dirt
roads. Consider using a water truck or trailer to wet dirt roads, especially
before travel during summer months when heat convection currents carry dust
well up into the tree canopies. Individual backyard trees can be hosed down in
early to mid-summer to remove dust and enhance biological controls.
Organically Acceptable Methods
Biological and cultural controls and sulfur and
certain oil sprays are acceptable for use on an organically certified crop.
Monitoring and Treatment Decisions
Look for sixspotted mite when monitoring persea mite (see MONITORING PERSEA AND SIXSPOTTED
MITES). Be sure to
distinguish the mite species present. When specifically monitoring for
sixspotted mite, select trees in dusty and more humid locations of groves. Use
a hand lens to examine along the midrib and lateral veins on the underside of
interior canopy leaves. Look for brown to purplish discoloring, mite webbing,
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.
||Amount to use
|When choosing a pesticide, consider
information relating to the impact on natural
enemies and honey bees
and environmental impact.
||NARROW RANGE OIL#
||MODE OF ACTION: Contact including smothering and barrier effects.
Requires good coverage to be effective. Check with certifier to determine which products are organically acceptable.
||MODE OF ACTION: Unknown. An inorganic miticide.
||COMMENTS: Do not
treat with sulfur when temperatures exceed 90°F to avoid leaf damage. Sulfur
sprays are often not effective in coastal areas where temperatures do not promote fuming action.
UC IPM Pest Management Guidelines: Avocado
UC ANR Publication 3436
B. A. Faber, UC Cooperative Extension, Santa Barbara/Ventura counties
J. G. Morse, Entomology, UC Riverside
M. S. Hoddle, Entomology, UC Riverside
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
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