Mealybugs are perhaps best known as pests of indoor plants. But occasionally mealybugs strike outdoors flowers and shrubs. The striped mealybug, Ferrisia virgata Cockerell, is one such pest that has been showing up in Texas gardens this summer.
Mealybugs are pests that feed on plant sap. Most are white in color, from a white wax produced by special glands on the tops and sides of their bodies. The patterns, form and length of the waxy filaments on mealybug bodies help us identify the different species of mealybugs. The striped mealybug is identified by two dark rows of punctures on the top (dorsum) of the insect, two long waxy tails on the end of the body, and fine needle-like rods extending out from the body, like a bad haircut.
While feeding, all mealybugs produce a sugary excrement that drops on leaves and stems and makes plants appear sticky. Once a leaf or stem is coated with this sticky secretion, known as honeydew, it eventually turns black as a result of black sooty mold growing on the sugary coating. The same type of excrement is produced by aphids, scales, and other sap-feeding insects.
Look for striped mealybugs on the stems, under leaves, on flower buds and in the leaf axils of infested plants. Because of their behavior of settling the protected crevices of plants, and their waxy coverings, don’t be surprised if you find these bugs difficult to control with insecticides.
Soaps and oil sprays may provide some control, especially if applied before an infestation becomes heavy. But good coverage is essential, as soaps and horticultural oil sprays only kill insects that are sprayed directly. Also, expect to need to spray several times. If certain parts of the plants are more heavily infested, pruning these stems prior to spraying may be helpful. Systemic insecticides like imidacloprid or dinotefuran are very effective on most sap feeding insects when applied as a drench to the soil. These products would be my first choice against a tough mealybug infestation.