Green shield scale—Pulvinaria psidii
This soft scale (family Coccidae) infests mostly broadleaves of subtropical and tropical origin. Hosts include anthurium, aralia, begonia, camellia, croton, ficus, hibiscus, gardenia, pittosporum, plumeria, Schefflera, Schinus, and Syzygium.
The scale is ovoid and brown, green, or yellowish. The body of mature females is slightly convex and 1/8 to 1/6 inch long. The adult female secretes a wide, cottony egg sac beneath her body that erupts around the margins. This differs from most soft scale species in California, where eggs remain hidden underneath the females' body. Males are not known in this species.
Green shield scale develops through three life stages: egg, nymph, and adult. After hatching from an egg, nymphs remain relatively mobile and can move to infest and feed on different portions of the plant or adjoining plants that are touching. There is one generation per year.
Green shield scale sucks phloem sap from leaves and thin-barked shoots. When abundant it produces copious honeydew on which blackish sooty mold grows. Mature females cover plants with flocculent white egg sacs. Long after the scales have died; this white wax can remain on plant surfaces, reducing plant aesthetic quality.
The mealybug destroyer is an important predator of green shield scale. Parasitic wasps also help control this pest if natural enemies are conserved (preserved). To increase the effectiveness of natural enemies, control ants, minimize dustiness (e.g., periodically hose off shrubs), and avoid the application of broad-spectrum, persistent insecticides. See Protecting Natural Enemies and Pollinators for more information.
When direct control is warranted after employing natural enemy conservation practices, infested terminals can be thoroughly sprayed with horticultural oil during the dormant season or when monitoring indicates that crawlers are active in the spring. See Pest Notes: Scales for more management recommendations, including the section "Monitoring" that discusses how to effectively time oil application.
Adapted from Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).
Adult female green shield scales and their cottony egg sacs.
Mature female green shield scale and egg mass.
First and second instar green shield scales.
Persistent wax of old egg masses of green shield scale.