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How to Manage Pests
UC Pest Management Guidelines
Floriculture and Ornamental Nurseries
Soft Scales
Scientific names: Brown soft scale: Coccus hesperidum
Hemispherical scale: Saissetia coffeae
Black scale: Saissetia oleae
Green shield scale: Pulvinaria psidii
(Reviewed 1/04,
updated 1/04)
In this Guideline:
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DESCRIPTION OF THE PESTS
Soft scales are typically found on woody and foliage plants. The first nymphal
instar is called a crawler and has
functional legs, while the remaining instars are attached to the leaf or twig
and (with the exception of green shield scale) do not move. These scales
typically have a more conspicuous profile from the side view compared with
armored scales and produce copious honeydew. The protective covering over a
soft scale cannot be separated from its body.
Brown soft scale adults are fairly flat
in profile, range in color from yellowish green to brown, and are often spotted
or mottled to uniform brown. Hemispherical scale adults are round, hard, brown,
smooth and shiny. Black scale adults
are globular and hardened with ridges on the back that look like the letter
"H". Green shield scale, introduced into California in the early 1990s, has a
light yellow-green color as an immature. Female green shield scales produce a
mass of eggs in a cottony ovisac without mating (i.e., reproduction is
parthenogenetic and there are no males).
DAMAGE
Soft scales remove sap from plants and cause yellowing of leaves and overall
plant decline. Green shield scale ovisacs and the honeydew excreted by all the
soft scales disfigure plants. Honeydew allows the growth of black
sooty mold fungi and attracts ants,
which may then carry scales to uninfested plants.
BIOLOGICAL CONTROL
The black scale parasite, Metaphycus helvolus, has also been used for
control of the closely related hemispherical scale. The mealybug destroyer,
Cryptolaemus montrouzieri, is known to be an effective predator of green
shield scale. Green shield scale,
however, is a CDFA "B" rated quarantine pest, so plant material must be
entirely free of the scale to be shipped.
CULTURAL CONTROL
Exclusion of windblown crawlers can be accomplished by covering openings to the
greenhouse with fine mesh screens. Prune out and discard heavily infested plant
parts. Control ants.
MONITORING and WHEN TO TREAT
Visual inspection of plants will help locate infestations and may permit
localized treatments of hot spots. The presence of ants climbing on the plant
can also indicate a problem with scales.
Treatment is generally warranted when scales are present. Optimum treatment
timing is when crawlers are active; however, this can be difficult when there
are overlapping, multiple generations. Multiple applications are
generally necessary.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide.
Before using a pesticide for the first time or on a new crop or cultivar, treat
a few plants and check for phytotoxicity.
| Class |
|
Pesticide (commercial name) |
Manufacturer |
R.E.I.1 |
Comments |
| insect growth regulator |
A. |
pyriproxyfen
(Distance) |
Valent |
12 |
Do not apply more than 2 times per cropping cycle or per 6
months. Do not apply through any type of irrigation system. |
|---|
| B. |
s-kinoprene
(Enstar II) |
Wellmark |
4 |
Apply prebloom. Also labeled for low volume use. Do not apply
through any type of irrigation system. |
|---|
| neonicotinoid |
A. |
imidacloprid
(Marathon 1G)
(Marathon II) |
Olympic |
12 |
Not to be used more than once every 16 weeks. Alternate with
insecticides that have a different mode of action to prevent development of
resistance to neonicotinoids. Do not apply to soils that are water logged or
saturated. Do not apply to bedding plants intended to be used as food
crops. |
|---|
| B. |
imidacloprid
(Marathon 60WP) |
Olympic |
12 |
As above. Apply only as a drench. |
|---|
| oil2 |
A. |
clarified hydrophobic extract of neem oil
(Triact 70) |
Certis |
4 |
Do not spray plants under stress. Target pest must be
completely covered with spray. Check label for list of plants that can be
treated. May cause injury to flowers. Do not use through any type of irrigation
system. |
|---|
| B. |
horticultural oil
Ultra-Fine Oil
SafTSide
JMS Stylet Oil |
Whitmire MicroGen
Brandt
JMS Farms |
4
4
4
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Use as above for neem oil. Also, do not use with sulfur fungicides; check label for tank mix restrictions.
|
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| organochlorine |
A. |
endosulfan*
(Endosulfan 3EC) |
Gowan |
24 |
Do not apply to ‘Bonnaton Deluxe,' ‘Fred Shoesmith,'
or ‘White Knight' chrysanthemums. Check local water/runoff restrictions.
Do not use through any type of irrigation system or apply more than 3 lb a.i./
acre/season. |
|---|
| organophosphate |
A. |
acephate
(Address) |
Dow |
24 |
Do not use through any type of irrigation system. |
|---|
| B. |
acephate
(Orthene T,
T&O Spray) 75WP |
Valent |
24 |
A number of chrysanthemum varieties have exhibited phytotoxic
reactions. In greenhouses only labeled for use on anthurium, cacti, carnation,
rose, orchids, some foliage plants, young poinsettia, and some varieties of
chrysanthemum. Can stunt new growth in roses. Do not use through any type of
irrigation system. |
|---|
| C. |
acephate
(PT 1300 Orthene TR) |
Whitmire MicroGen |
24 |
An aerosol for greenhouse use only. |
|---|
| D. |
chlorpyrifos*
(PT DuraGuard ME) |
Whitmire
MicroGen |
12 |
|
|---|
| E. |
malathion
(various) |
various |
12 |
Not for greenhouse use. |
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UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Insects and Mites
K. L. Robb, UC Cooperative Extension, San Diego Co.
H. S. Costa, Entomology, UC Riverside
J. A. Bethke, Entomology, UC Riverside
M. P. Parrella, Entomology, UC Davis
Acknowledgment for contributions to the insects and mites section:
R. S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT
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