I have two large hollys on the south side of the house. They are infested with something. The interior of the shrubs black leaves and on the leaves are the egg casings pictured. What is it and how do I treat it without harming birds, bees or butterflies? Thank you
Carroll County Maryland
This looks like cottony camellia scale, a sucking insect on the leaf undersides. These are eggs masses. Crawlers will hatch from the eggs. Here is more about them https://extension.umd.edu/hgic/topics/cottony-camellia-scale-shrubs
Since these are large trees spraying may be difficult or impractical. You may want to hire a landscape professional to apply a treatment for you. A landscape professional would have access to other types of (stronger) insecticide products and equipment to treat large trees more effectively, for example, imidicloprid or dinotefuron.
The insecticides can be applied later in the season as the plants may be flowering now. No controls are recommended now.
If the infestation is heavy, A "dormant oil" to manage overwintering scale in the dormant season (when leaves have fallen from deciduous trees) can be applied. Thorough coverage of all plant surfaces, including undersides of the leaves, is important for effectiveness.