Description: Scale insects are commonly mistaken for something other than an insect. They are small, immobile and are covered in a waxy coating. Further complicating matters is the fact that there are over 150 different types of scale. Many are common on our Carolina landscapes and cause serious problems when they appear. They get their name from the fish scale-like covering they surround themselves with for protection. Most scales range in size from 1/8 to 3/16th of an inch in length. Wax scale is commonly found on hemlocks, laurels, and holly.
Symptoms: Scale insects feed on the sap in leaves and stems of ornamental plants. Their mouthparts are six to eight times longer than their body. Once they pierce the plant and begin to feed, the plant starts to lose vigor. Symptoms include yellowing stunted growth and premature leaf drop. Scales reduce the vitality of plants, making them susceptible to other pests and diseases that can often be fatal. Another result of sap feeding insects is sooty mold. Because they consume large amounts of plant sap, they excrete a lot of ‘honeydew’. Once on the leaf, this sticky substance grows a black mold that can interfere with photosynthesis and further weaken the plant.
Action: Adult scales, because of their waxy coating, are not easily controlled by insecticides. With proper timing, insecticides can be used in the crawler stage, before they produce the waxy coat. Smothering scale with horticultural oil is another control method. Don’t over fertilize. Scale is attracted to new growth, brought on by heavy doses of nitrogen. Sooty mold can be washed off with some effort. Horticultural oil applications can help loosen it and make it easier to wash away.
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