COTTONYCUSHION SCALE
COMMON NAME: Cottonycushion scale
SCIENTIFIC NAME: Icerya purchasi (Order: Homoptera)
DESCRIPTION: ADULTS - The female is about 1/4 inch (5 mm) long, yellow, red, or brown in color, but covered with a dense white waxy "shell". She appears rather "dome-like" and does not move about. The male is smaller, less than 1/16th of an inch and looks rather like a tiny, skinny fly with two wings and two tufts of hair on the posterior end. EGGS - The bright red eggs are carried under the ridged, wax-like shell of the female. NYMPHS - The nymphs are bright red with black or brown legs and long antennae. You will generally find "colonies" of these scales with many stationary adult females and mobile nymphs all together.
LIFE CYCLE: The egg mass (containing from 500-1,000 eggs!) hatches in warm weather and releases the nymphs. They feed on the plant juices in foliage and twigs and eventually become covered with the cottony wax which helps protect them from the weather and predators. Males spin cocoons, then transform into winged adults who do not feed, but whose only function in life is finding a mate. Mated females lay eggs which later hatch into a new generation of males and females. Unmated females may also lay eggs, but these will only produce more females. There may be many generations per year.
HOST PLANTS: Apples, apricots, citrus, peppers, potatoes, pines, landscape trees and shrubs and walnuts.
TIME OF YEAR: Just about any time in Southern Arizona if we have a warm winter.
WHAT TO LOOK FOR: "Lumps" on the stems of your plants. Sometimes found on the plain bark but more often at the junction of stems and twigs.
PROBLEMS AND DAMAGE: A few won't do much damage, but populations can build up quickly and heavy feeding can cause discolored leaves, leaf drop, reduced growth and vigor, and stunted plants. These insects secrete a "honeydew" that can attract ants and also support a growth of sooty mold that can further damage the plant.
CULTURAL CONTROLS: If appropriate for your plant species, use a dormant oil to smother overwintering insects and eggs.
COMPANION PLANTING AND REPELLENTS: None noted.
TRAP PLANTS: NA
MECHANICAL CONTROLS: If you just find a few, scrape them off with your fingernail or use a brush of some sort. A forceful spray of water from the hose will dislodge many of the pests and a spray of soapy water will dissolve the waxy outer covering and kill both adults and the less-protected nymphs. The addition of 1 tablespoon of rubbing alcohol to the soap and water mixture will greatly improve its effectiveness. If you have just a few pests or they are located on an indoor plant, you can just use alcohol on a cotton-tipped swab and literally "wipe away" the problem.
NATURAL CONTROLS: Ladybird beetles (Ladybugs) are a natural scale control.
BIOLOGICAL INSECTICIDES: An insecticidal soap (such as Safer's, etc.) is effective against this pest and can be made even more so with the addition Of a little rubbing alcohol if your plant species can tolerate it.
CHEMICAL CONTROLS: Please consult the Agricultural Extension Agent or a Master Gardener volunteer for current recommendations (Tel. 458-8278 ext 2141 in Sierra Vista or 384-3594 in Willcox). Whatever you use, FOLLOW LABEL DIRECTIONS EXACTLY and take the necessary precautions to protect yourself, other humans, non-target animals, and the environment.