How to Manage Pests
UC Pest Management Guidelines
Latania scale: Hemiberlesia lataniae
California red scale: Aonidiella aurantii
Dictyospermum scale: Chrysomphalus dictyospermi
Greedy scale: Hemiberlesia rapax
In this Guideline:
Armored scales are rarely a problem on avocados in California.
Armored scales (family
Diaspididae) have a flattened, slightly convex cover that at maturity is about
0.06 inch (3 mm) in diameter. This platelike cover usually can be removed to
reveal the actual scale body underneath. Armored scale covers typically have a
different colored, slight protuberance (exuviae or "nipple") and concentric
rings, which form as each nymphal stage enlarges its cover. Females develop roundish covers. For species with males, their covers are elongate in late
Latania and greedy scale
can reliably be distinguished only by an expert. Their covers are gray, tan, or
white. Dictyospermum scale has a yellowish brown cover that is somewhat darker
than the similar-looking, orange to reddish California red scale cover.
California red scale and latania scale occur throughout the plant, with
relatively even distribution among fruit, leaves, and wood. Dictyospermum scale
infests mostly fruit and leaves. Greedy scale is usually limited to twigs and
Latania scale and
greedy scale females lay eggs beneath their cover, from which crawlers hatch. California red
scale and dictyospermum scale give live birth to young crawlers. Greedy scale and
latania scale reproduce without males, at least in California. Both California
red scale and dictyospermum scale produce males,
which as immatures develop under elongate covers.
Scales in avocado are usually under good biological control. Latania
scale occasionally damages avocado. High latania scale populations on bark can
kill twigs, especially on young trees. Unlike many plant-sucking insects,
armored scales do not secrete any noticeable liquid. Economic damage is from
scale covers on the fruit skin, which appear as tiny dimples or light-colored
spots. Feeding may also cause small discolored spots in the skin. Internal
fruit quality is not impaired, but infested or spotted fruit may be culled.
California red scale is a rare problem, and only on avocado near citrus.
Dictyospermum scale and greedy scale occur in avocado only at innocuous
Biological control is the primary scale control method. Conserve
natural enemies by controlling ants, minimizing dust, and avoiding application
of broad-spectrum, persistent insecticides. If certain areas of a grove have
high armored scale populations, determine whether encrusted fruit can be
selectively harvested and sent to a packing house that uses brushes or
pressure-washing equipment that can remove scale covers from fruit. In the
infrequent event that direct control may be justified, oil spray has little
long-term adverse impact on natural enemies. Time any scale treatments to occur
soon after most scale crawlers have emerged.
insects and parasitic wasps control most scales. Armored scale parasites
include species of tiny Aphytis and
Aphelinidae), and Comperiella and Signiphora (family
Encyrtidae). Most scale predators feed on both armored and soft scales and
often on other pests. Predators include brown and green lacewings,
pirate bugs, predaceous mites such as Cheletomimus
berlesei and Hemisarcoptes malus, and sixspotted thrips.
include the spotless lady beetle (Cycloneda sanguinea), steelblue lady beetle (Halmus
chalybeus), and twicestabbed lady
beetle (Chilocorus orbus =C.
stigma). As adults,
these lady beetles are about 0.16 to 0.2 inch (4–5 mm) long. Spotless
lady beetle has a black and white head and thorax and orangish wing covers
without markings. Steelblue lady beetle is metallic bluish. Twicestabbed lady
beetle is shiny black with two large orangish spots on its wing covers. Its
larvae are black to brownish with a yellowish transverse band and are covered
with branched spines.
control and some oil sprays are acceptable for use on an organically certified
Monitoring and Treatment Decisions
In the rare
situation where treatment is warranted, spray oil after the end of maximum
crawler emergence. To time an application, monitor scale crawlers by trapping
them with transparent tape that is sticky on both sides. Wrap tape traps
tightly to encircle each of several twigs near female scales. Replace traps
weekly when crawlers are expected. Preserve traps sandwiched between clear
plastic and light blue paper, and label papers with the trap date and location.
Visually compare crawler abundance in traps among monitoring dates. Treat when
it is obvious that more crawlers per trap were caught during previous weeks and
catches have definitely declined. If persistent populations of California red
scale are present, consider releasing a small number (perhaps 10,000) of Aphytis
melinus near the scale infested trees after purchasing them from an
||Amount to use
choosing a pesticide, consider information relating to the impact on natural enemies and
and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
||NARROW RANGE OIL#
OF ACTION: Contact including smothering and barrier effects.
||COMMENTS: Requires good coverage to be effective.
Oil does kill some beneficial wasps and suppresses beneficial mite
populations, however the residue does not persist and parasitic wasps can
emerge from parasitized scale or be commercially released soon after
treatment. Check with certifier to determine which products are organically acceptable.
||About 10,000 per infested site
For release against California red scale only. Make a single release, or
several smaller release at about 2 week intervals, totaling approximately
10,000 parasites per infested site. Time release so that the parasites can
attack unmated female scales. Visually monitor scales and release parasites
when a significant proportion of the scale population is at or approaching
the virgin female stage. Alternatively, monitor using pheromone-baited sticky
traps and release parasites at or just before a male flight, which is approximately 800 degree-days after the peak of the previous generation male scales.
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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