What are those white spots on the magnolia leaves? They may not look like insects, but they are; scale insects. Scale are very sedentary insects, spending most of their lives beneath a protective, shell-like covering, with their mouthparts embedded in their plant host. Most species of scale are only able to crawl about for a brief period immediately after they have hatched from the egg, as “crawlers.” Once they insert their mouthparts into a plant and begin feeding, most female scales are confined to that spot for the remainder of their lives. For species that produce males, the adult males are winged.
There are two major types of scale, soft scales and armored scales. One important difference between these two groups is that soft scales produce lots of honeydew, while armored scales do not produce honeydew. False oleander scale is an armored scale. This is a non-native scale that has spread throughout the Southeastern Coastal area over the past few decades.
False oleander scale seems to have become more common in recent years, especially in the southern half of the state. The female scales are hidden beneath those flattened, pear-shaped covers. Males produce a more elongate, 3-ribbed white cover and are more often found on the undersides of leaves. These scale feed primarily on leaves, where they cause chlorotic, yellow areas. Heavy infestations can cause premature leaf drop and unthrifty plants. In addition to oleander, false oleander scale also attacks aucuba, banana shrub, palms, including sago palm, and magnolias. In Mississippi landscapes, heaviest infestations are most often seen on sago palms or magnolias. In fact this scale is also known as magnolia white scale.
Control: Magnolias and other plants often harbor low infestations of these scale with relatively little ill effects, but heavy infestations can cause plants to be unsightly and to suffer reduced growth. Soil-applied treatments of products containing the active ingredient dinotefuran (Safari and Zylam are examples—but these are only sold in commercial quantities) are some of the most effective treatments for these and other armored scale. These treatments work systemically, being absorbed by the roots and traveling up through the vascular system to leaves, where they are consumed by the scales. Plan on treating two successive years for best results. Timely sprays of horticultural oils, such as Volck Oil Spray or Year Round Spray Oil, can also be useful on smaller plants, but thorough spray coverage is required for good control.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service. The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
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