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How to Manage Pests

UC Pest Management Guidelines


Colony of brown soft scale.

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:


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


Use as above for neem oil. Also, do not use with sulfur fungicides; check label for tank mix restrictions.

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.
1 Restricted entry interval (hours)
2 Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
* Restricted use pesticide. Permit required for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

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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Statewide IPM Program, Agriculture and Natural Resources, University of California
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For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r280301211.html revised: June 13, 2005. Contact webmaster.