Cottony Tufts on Holly and Other Broad Leaf Evergreens
This week I found cottony camellia scale ovisacs on hollies in my yard and on campus. Cottony camellia scale, Pulvinaria floccifera, is related to other cottony scales such as cottony maple leaf scale, Pulvinaria acericola, and cottony maple scale, Pulvinaria innumerabilis. Cottony camellia scale seems most common on hollies but is also a pest of euonymus, camellias, and other broad leaf evergreens. The adults lay eggs on the undersides of leaves in late spring and early summer. The ones I found have probably been present for a week or two (sorry I can’t look at every plant everyday) though no crawlers were present. Crawlers hatch and find a feeding site on the underside of the leaf and settled down to feed on phloem throughout the summer. In spring adults continue feeding then produce ovisacs that contain several hundred eggs.
Cottony camellia scale produce a lot of honeydew that causes holly leaves, particularly inner leaves, to get covered in black sooty mold. Control of these scales could include systemic neonicotinoids such as imidacloprid, dinotefuran, thiamethoxam, or acetamiprid. Consider the product labels when selecting these (or any) insecticide. Neonicotinoids and most other insecticides cannot be applied when plants are blooming. Hollies are finishing blooming now but when scale ovisacs first showed up they were in full bloom. Depending on the level of infestation and the tolerance for some scales horticultural oil could be used to maintain scales at low levels. Just be sure to cover the bottom of leaves and inner leaves.