What is on my salvia?
The messy, cottony mass is caused by a piercing/sucking insect called a mealybug. One of the more common groups of scale insects attacking ornamental plants. There are about 275 species of mealybugs known to occur in the continental United States making it difficult to identify exactly which one is causing this problem. Because of the difficulty, I sent the photo to the University of Florida and an entomology specialist identified it as a mealybug.
Damage to the plants is caused by mealybugs piercing into the plant tissue and feeding on the vascular fluid of the plant. While the insect is feeding, it can also inject toxins or plant pathogens into host plants potentially causing serious diseases. In addition, mealybugs secrete a waste product called “honeydew”, which is a sweet liquid. This liquid drops on the leaves, coating them with a shiny, sticky film. Mold from the surrounding air attaches to the surface of the honeydew creating a black substance called sooty mold. I am often asked how to control the sooty mold and I remind clients to manage the insects and the mold will disappear.
There are other symptoms of mealybug feeding – premature leaf drop, die-back, and potentially killing the plant if left unmanaged. Another interesting thing to watch for – mealybugs and other piercing-sucking insects will be protected and guarded by ants who feed on the honeydew.
While managing the mealybugs it is also important to manage the ants. An adult female mealybug many lay up to 600 eggs – no wonder they create such a mess. An exception is the long-tailed mealybug which bears its young live. Most mealybugs will take about one to two weeks to go from egg to crawler. Crawlers can move to another site on the plant. The crawler stage is the best time to manage mealybugs with insecticidal soap. Once the crawler finds a suitable site to feed, it anchors itself and does not move.
Males are winged and only live a short time and their purpose is to find a mate. Females do the feeding and damage on plants. Avoid using broad spectrum insecticides like malathion or carbaryl (these are the active ingredients in the pesticide) as these can kill our important pollinators. Please minimize use of high nitrogen and overhead irrigation as these practices tend to contribute to insect and disease issues.