Cottony cushion scale is a very common insect pest of many garden plants, including citrus trees, Nandina, Pittosporum and rose. Its cottony white egg sac and heavy honeydew production make it easy to spot in plants. This must be a good year for the insect, because many gardeners are spotting it and wondering what is and how to deal with it.

The female cottony cushion scale is bright orange, red, yellow or brown, but what most people notice is the elongated, ridged, white cottony egg sac that is attached to its body. The sac contains up to 800 eggs, and may become two or three times as long as the body, resulting in an overall length of almost 1/2 inch. The eggs hatch in a few days in summer, but take up to 2 months to hatch in winter. The immature scales or "crawlers" are red with dark legs and antennae, and you can usually see them wandering around the scale colony. Cottony cushion scale usually has three generations a year, and unlike other scales, it can move around throughout its life.

Like other scales, cottony cushion scale weakens its host by sucking sap from the leaves, twigs, branches and trunk. A heavy infestation can result in defoliation and dieback of twigs and small branches. Gardeners may not notice the scale until leaves begin to drop, exposing the scale colony on the inner branches of the tree or shrub. Like certain other scales, cottony cushion scale excrete honeydew, which is usually accompanied by sooty mold and ants.

Cottony cushion scale is often controlled by two introduced natural enemies. The most famous is the vedalia beetle, a lady beetle which was introduced from Australia in the 1890s and saved California's young citrus industry from destruction by the scale. If you find cottony cushion scale colonies, look for the black and red vedalia beetles near the scale egg sacs. The other natural enemy is a parasitic fly which deposits its eggs inside the scale body; the eggs hatch into larvae, which feed within the scale.

You can help control cottony cushion scale by controlling ants. Apply a band of sticky material such as Tanglefoot or Stickem to the trunks of trees and shrubs. Or, use baits such as diazinon granules. For the most effective control, treat in late winter or spring when the ant populations are low.

If the scale colony has grown to the point of causing your plant to decline, you will want to take more direct action. You can control the scale by spraying with a narrow-range oil during the dormant season, or spray the foliage when the small reddish scale crawlers are active. You can also control the scale with insecticides such as carbaryl (Sevin) or diazinon, but remember that these will also kill any natural enemies that are present.