Are these 'true bugs' infesting your Wilmington home garden?

“Scale” on woody ornamentals is among the most frequently reported and diagnosed pest problems at the Cooperative Extension Plant Clinic in New Hanover County. But what exactly is this issue and how do you treat it?

Scales are plant-parasitic members of the diverse insect order Hemiptera (“true bugs”). Together with the mealybugs, they comprise the superfamily Coccoidea with over 8,400 species worldwide. The entire life of a female scale is spent on the plant she parasitizes. Upon hatching from an egg, she will live freely as a “crawler” on the host plant for a few molt cycles before sealing herself to a leaf, branch, twig, or petiole. She will secrete a coating around her body and lose the ability to move. All the while, she is sapping sugars and nutrients from the host with a stout proboscis.

Upon mating with a male, she fills the armored cavity around her with eggs, protecting them until they hatch. Male scales differ from species to species, but often they don’t resemble the female at all. In many species they are rare, free-living winged insects.

If any subdivision of scales is worth knowing, it is the armored scales, family Diaspididae. These insects secrete a particularly tough scale made of wax and cast exoskeletons from earlier molts. They include the familiar false oleander scale (Pseudaulacapsis cockerelli) of magnolias, the gloomy scale (Melanapsis tenebricosa) of maple, and the tea scale (Fiorinia theae) of camellia. These scales are impervious to most spray pesticides, and it is most effective to target the soft-bodied crawlers.

Other families of more soft-bodied scales are also important in our area. These scales may secrete sugary liquid that causes blackening of foliage due to sooty mold growth. This can be a significant aesthetic problem in heavy infestations. The ground pearls (family Margarodidae) are unusual in that they attach to hosts underground at the root. They are serious untreatable turf pests in our area.

If you find a scale infestation in your home landscape, try to select the least drastic measure first. This will limit harm to the populations of native pollinators and beneficial insects. Note that virtually all scales of economic importance in our area are non-native, having been introduced from other continents by humans. Where feasible, a few applications of horticultural oil (or insecticidal soap) combined with mechanical removal of adults will eliminate the problem. Apply the product in summer, but not when temperatures exceed 85 degrees.

Heavier infestations may stunt growth, discolor leaves, and in extreme cases be a primary cause of decline. Careful application of system insecticides such as dinotefuran may be warranted in these cases. Always follow the label when using these products. The scales may remain attached to the host after death.

Finally, remember to be vigilant of the crape myrtle bark scale (Acanthococcus lagerstroemiae). This brand-new exotic pest appears to be spreading in Wilmington because crape-myrtle trees are overrepresented in our canopy. Please visit the Plant Clinic, NC Cooperative Extension-New Hanover County Center at the Arboretum, 6206 Oleander Drive in Wilmington weekdays between 10 a.m.-4 p.m. information on how to identify and treat scales. The gardens are free and open daily 8 a.m.-5 p.m.

Miles Buddy is the Consumer Horticulture Program Assistant and can be reached at 910-798-7660 or mmbuddy@ncsu.

This article originally appeared on Wilmington StarNews: Are scale insects infesting your home garden in Wilmington, NC?