Soft Scales
Black Scale Saissetia oleae
Hemispherical Scale Saissetia hemisphaerica
Soft Brown Scale Coccus hesperidum
Nigra Scale Parasaisetia nigra
Description
The Black Scale is dark brown or black, oval, and convex. It is easily recognized by a raised H-shaped on its dorsal (upper surface) and somewhat roughened appearance.
Figure 1. Brown Soft
Scale on Citrus
Hemispherical Scales appear smooth, strongly convex, shiny, brown, and roughly circular in outline. Immature stages (crawlers) are white and have the typical "H" shaped pattern typical of the above mentioned black scale.
The Soft Brown Scale is oval and more flattened than either the black or hemispherical scales: It is a pale brown, dirty white or grayish mottled with dark brown on the back. The shell is pliable. An additional species, the long or elongate soft scale is similar in appearance, but more elongate.
Figure 2. Brown Soft
Scale on Staghorn Fern
The Nigra Scale varies in size, shape and color depending on its host. It may appear slim and elongate when found on thin stems or petioles or oval when on leaf blades. Its outer shell is hard and shiny black or dark brown. Adult male scales are usually rare, tiny, and either winged or wingless. They only live long enough mate with the females and then die.
Life History
Scales are similar in habit to mealybugs in that they feed on plant sap. They are usually found on the undersides of the leaves and stems, but may be found on the upper leaf surface on some hosts. Generally older and younger leaves may be attacked, but scales on stems usually prefer the new succulent growth. Out-of-doors scales only produce 1 - 2 generations per year, but under greenhouse conditions they may have 3 - 6 generations per year often with overlapping between successive generations. Generally,' the female scale will lay as many as 2,000 eggs beneath her outer shell. With the soft brown scale, only 1 or 2 live young are born at a time over a period of several months. Young crawlers, similar to mealybugs, emerge after several days or weeks and migrate over the host plant looking for a feeding site. Soft brown and hemispherical scale crawlers are sluggish and only move a short distance from the female. Scale crawlers progress through 3 growth stages before changing into adults. Scale crawlers are usually paler in color and flatter than the adult female. Following egg laying, the female dies. Most scale species prefer humid and warm conditions with shade. Extremes in temperature appear to be detrimental. A scale generation occurs about every 2 months under greenhouse conditions.
| SCALE SPECIES | HOSTS |
|---|---|
| Black Scale | Weeping Fig, Citrus, Banana, Olive |
| Hemispherical Scale | Ferns, Schefflera, Asparagus Fern, non-woody evergreens |
| Soft Brown Scale | Schefflera, Weeping Fig, Ferns, Citrus |
| Nigra Scale | Weeping Fig, Citrus, Ivy, Holly |
Damage
Feeding by soft scales is similar to mealybugs resulting in a distorting, stunting, and yellowing of the foliage. Honeydew is also produced allowing for sooty mold development.
Nonchemical Control
Pruning out of heavily infested plant parts, use of predators, such as the green lacewing, and parasitic wasps can be effective.
Chemical Control
Insecticidal sprays for control of crawlers may be applied.