Small cottony masses with long, waxy filaments extending from one end is a symptom of the Long-tailed Mealybug, Pseudococcus longispinus, which is a sucking insect that colonizes on the least accessible parts of plants. Since it is hard to see, systemic insecticides are preferred, but thorough treatment with a contact insecticide may provide control. Infested plants will have honeydew and sooty mold (black coating) on the leaves. Terminal leaves may become yellow and distorted, and dieback may occur. Infested plants are usually growing in sheltered locations, such as against south facing walls. The mealybugs may be found on lower leaf surfaces and stems. Adult mealybugs are about 1/8 inch long, and covered with white wax. The body margin is ringed with white wax filaments, with the last pair over 1/2 the length of the body. Immature mealybugs have short wax filaments. This mealybug feeds on pyracantha, holly, yew, and rhododendron. There are two to three generations a year, and the immatures over-winter on the bark. Inspect plants for beneficial predators such as ladybird beetles. Some immature ladybird beetles may resemble the mealybugs, but move faster. Check carefully before spraying with an insecticide. A horticultural oil may be sprayed on dormant plants to reduce the over-wintering population. A 2% summer rate of horticultural oil will reduce the numbers of mealybugs during the growing season if the coverage is thorough. If mealybugs are densely packed on leaves, spray with a systemic insecticide. If the mealybug problem persists, ant control may be necessary. Ants feed on the honeydew secreted by the mealybugs and protect them from parasites and predators.

Hope this helps.

Thanks Rhodyman. I found the info quite useful and will address it with the horticulture oil you cited.