HEMISPHERICAL SCALE
Depending on the
host plant, the adult scale may vary in size. The scale varies from 1/8 inch
on Cycas 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.
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.
| Pesticide | (Trade Name) | Formulation and Amount |
| acephate | (*Orthene) | 9.4% emulsifiable concentrate: Outdoors only: 3 tablespoons per gallon of water |
| acephate | (Orthene) | 75% soluble powder: 2/3 pound per 100 gallons of water |
| azadirachtin | (Azatin XL, *BioNeem) & others | 3% emulsifiable concentrate: 1/2 teaspoon per gallon of water |
| cyfluthrin | (Decathlon) | 20% wettable powder: 1.9 ounces per 100 gallons of water |
| fenoxycarb | (Precision) | 25% wettable powder: 1/2 teaspoon per gall of water |
| imidacloprid | (Marathon) | 60% wettable powder: greenhouses and nurseries - apply as drench |
| *imidacloprid | (Merit) | 75% wettable powder: landscapes and interiorscapes - apply as drench |
| kinoprene | (Enstar II) | 65.1% emulsifiable concentrate: 5 to 10 ounces per 100 gallons of water |
| lambda-cyhalothrin | (Scimitar GC) | 10% water soluble packets: 2 to 4 packets per 100 gallons of water |
| *malathion | 50 to 57% emulsifiable concentrate: 2 teaspoons per gallon of water | |
| *horticultural oil | (horticultural or summer) |
98 to 99% emulsifiable concentrate: 8 teaspoons per gallon or water |
| *pyrethrins | (Pyrenone, PyGanic& others labeled for homeowners) | 6% emulsifiable concentrate: 1/8 to 1-1/2 teaspoons per gallon of water |
| *soap | (M-Pede, Olympic, Safer's) | 50.5% emulsifiable concentrate: 2 to 5 tablespoons per gallon of water |
* Suitable for home use.
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
Prepared by: James R. Baker, Extension Entomologist Emeritus; Photo from University of Minnesota.
ENT/ort-30
August 1994 (Revised) April, 1998
Web page last reviewed January, 2008 by the webperson.
