Wax scales (insects) have become a serious problem in some parts of Georgetown and perhaps other sections of the city and also in Alexandria. They may be in many gardens without the owners being aware of them.
Mrs. J.D. Beam, president of the Georgetown Garden Club, appeals to all residents to join in an effort to get rid of them. "Wax scale is spreading from garden to garden and each resident should check his garden and spray at the proper time if necessary," she says.
The scale looks like a drop of white or dirty-gray wax, about one-fourth inch in diameter. It is attached along the stems, never on the leaves. A severe infestation may kill the plant in about three years. The waxy covering protects it from sprays. It feeds by sucking juice from the plant. Chinese and Japanese holly, pyracantha and euonymus are among the favorite food plants but almost all kinds may be attacked.
Each female (all of those that over winter are females) is capable of laying up to 2,000 eggs in the spring. The mother then dies, the egg-laying process kills her. Her body with the waxy coating protects the eggs.
The eggs start hatching about June 12 in Washington, a day earlier in Alexandria and Arlington, a day or two later in Silver Spring and Takoma Park.
Young scales are about the size of a speck of pepper and pink in color. They have legs and crawl around the first two days after hatching. Then they settle down for the remainder of their life.
It is during this crawler stage that the insects are spread to adjacent plants by the wind or birds or whatever. They are capable of crawling about 50 feet. It is also the time when they are easy to destroy. They do not have the waxy protective covering.
If you have wax scale on plants in your garden (look carefully to see if you do), start checking them with a magnifying glass about June 10 and daily until crawlers are observed. Then spray with Spectracide or Malathion. Tests have shown Spectracide to be more effective. Make three applications, two weeks apart. Directions on the label should be read and followed closely. These sprays should not be harmful to birds.
Spray early to keep the crawlers from getting to your neighbor's plants.
With heavily infested shrubs, it may be a good idea to cut off badly encrusted stems before the eggs hatch and destroy them. Don't throw them on the trash heap because the eggs will hatch there and insects spread to nearby plants.
The crawlers show visible white waxy secretions by the third day after hatching. As time goes on, the waxy covering develops to a point where it protects the insect from spray injury.
It used to be thought that the northern limit of wax scale was well below the Mason-Dixon line. Now no one knows how much winter cold it can endure and survive. Twenty years ago it has become serious in southeast Virginia, the Richmond area, Alexandria, Fairfax, Arlington, District of Columbia, Baltimore, and on the eastern shore of Maryland and Virginia.
The earliest records of established infestations were 1957 from Williamsburg for Virginia and 1959 from Annapolis for Maryland.
It had been hoped that a severe winter might greatly reduce the number. Some have been killed by cold weather but not really enough to make any difference.
The females have four growth stages. The reddish-brown crawlers (stage 1) show visible wax secretions by the third day, which is the beginning of stage 2.
Stage 2 is called the "cameo" stage because of the conspicuous paired tufts of dry white wax on the margins, and the prominent dorsal patch of white wax on the reddish-brown body. Stage 2 lasts about 37 days. Occasionally males found with the females in the cameo stage in 1967 and 1969 were white and slightly more elongate than the females.
Stage 3 is called the "duncecap" stage because of the increased secretion of soft wax from the marginal glands and the prominent conical accumulation of soft wax which blends into a continuous covering over the scale body.
Stage 4, is the female adult, starting about Sept. 1 to about Oct. 1.
Studies on the control of wax scale were initiated at the Beltsville (Md.) Research Center in 1966 under the direction of Dr. Floyd F. Smith. (
Three different methods of treatment were tested, using different kinds of insecticides, at different stages of growth of the insect. Most of the insecticides tested were far too dangerous to be handled by other than skilled applicators. They will not be named here.
Smith succeeded in getting 99.1 percent control with Cygon and 97.8 with Diazinson (sold as Spectracide), by spraying within 30 days after hatching. A summer oil (such as Volck Supreme) with ethion gave a 100 percent kill at the same time. Malathion gave only about 90 percent control.