Ornamental masthead

HEMISPHERICAL SCALE

Steven D. Frank, Extension Entomologist

CAUTION: This information was developed for North Carolina and may not apply to other areas.

General Information

HEMISPHERICAL SCALE, Saissetia coffeae (Walker), Coccidae, HOMOPTERA

scale imageDepending on the host plant, the adult scale may vary in size. The scale varies from 1/8 inch on Cycads to as small as 1/16 inch on asparagus fern. Relatively hemispherical, brown, smooth, and shiny, the scales may resemble a miniature army helmet. Young females may have a pattern of ridges in the form of the letter "H" on the dorsal surface.
The oblong, pinkish-beige eggs are very small and are protected by the mother's body in a mass of hundreds. The flat, pinkish beige crawler is about 1/32 inch long with two red eye spots. The antennae and legs are short and spindly. There are two setae protruding from the rear. Nymphs are semitransparent, light yellow or pink, and flat (young) to humped (older). They are so closely attached to the host plant that the legs and antennae are concealed. Two pale lines start at the margin on each side and fade in intensity toward the middle. Nymphs and young adults may exhibit the characteristic "H" pattern of the black scale group.

Biology

From its probable origin in South America, the hemispherical scale insect is now found in greenhouses and interiorscapes throughout the United States. The hemispherical scale insect has a wide range of hosts including bamboo, camellia, chrysanthemum, crape myrtle, croton, ferns, figs, gardenia, honeysuckle, lily, orchids, and zamia. The secretion of honeydew and subsequent formation of sooty mold detracts from the beauty and commercial value of the plant. Feeding stunts the plant and causes it to lose its leaves.

The hemispherical scale insect is a tropical insect that has become a common greenhouse pest. In warmer temperate areas, the scale can live outside. Unlike many other scales, the hemispherical scale secretes little wax. However, the scales do produce much honeydew that allows sooty mold to grow. Males are unknown and reproduction is by parthenogenesis. Each female may deposit up to 1000 eggs. After laying the eggs, the female dies and her body shrinks to form a cup or helmet over the eggs. Development for the egg stage and the three nymphal instars requires at least 40 days and may take as long as 105 days. There may be several generations each year in the greenhouse, with all stages being present at any one time. The nymphs do not move much once they have begun to feed. The hemispherical scale insect has a low rate of parasitism indoors, and it often becomes a serious pest.

Control

Like other scale insects, hemispherical scale can be difficult to control because the body of the mother protects the eggs and young nymphs. This is especially true if trying to manage them with contact insecticides such as pyrethroids.  Systemic insecticides will provide more reliable control because they make the plant toxic to feed on rather than having to contact the insect directly. The following pesticide formulations should control hemispherical soft scales if applied to infested plants thoroughly. A second application may be necessary later in the season.  Systemics such as dinotefuran and imidacloprid can be applied as a foliar spray or drench.   Others such as acetamiprid can only be used as a foliar spray.  Thus, efficacy relies on reading the label and using each product properly.  Never set an ornamental plant out in the sun to treat it; pesticide injury may result. Keep treated plants in the shade or treat during the cooler parts of the day so the foliage will dry before the plant is exposed to direct sunlight.

Table 1. Insecticides labeled for use on ornamental plants to manage soft scale in greenhouses (G), nurseries (N), and landscapes (L).
* Suitable for home use.

Active ingredient

Trade name

Labeled location

Activity

 Signal word

 IRAC
MOA
group

Compatible with
beneficials

acetamiprid

TriStar

G, N, L

Translaminar Systemic

Caution

4A

Yes

buprofezin

Talus

G, N

Contact

Caution

16

Yes

dinotefuran

Safari

G, N, L, I

Systemic

Caution

4A

Yes

horticultural oil

*many

G, N, L, I

Contact

Warning

-

Yes

imidacloprid

Marathon II

G, N, I

Systemic

Caution

4A

Yes

imidacloprid

*Merit

G, N, I

Systemic

Caution

4A

Yes

insecticidal soap

*many

G, N, L, I

Contact

Warning

-

Yes

pyriproxyfen

Distance

G, N, L

Translaminar

Caution

7C

Yes

thiamethoxam

Flagship 25 WG

G, N

Translaminar Systemic

Caution

4A

Yes

 

hemispherical scale

Hemispherical scale on rabbit foot fern.

More information on management of soft and armored scale available in Insect Note 156 and Note 157.


Other Resources

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.

© 2001 NC Cooperative Extension Service

Originally Prepared by: James R. Baker, Extension Entomologist Emeritus; Photo from University of Minnesota. and S. Frank.

ENT/ort-30
August 1994 (Revised) April, 1998. Revised Aug. 2010 by S. Frank.

Web page last reviewed January, 2011 by the webperson.