Question
Recently I have noticed black spots on one of my camellia bushes in front of my house.  Comparing it to the bush on the other side of the porch the leaves have a yellow hue and there are black spots on the leaves.  What can this be and how can I treat it.  I planted it a couple of years ago and up to now it has been healthy. This is the first year it has flowers and want to save it.  Thanks for any tips.

Answer
Sounds like tea scale. These can be controlled in the spring using an insecticide.
The most common insect pests of camellia are scales. Scale insects feed on plants by piercing plant tissue and sucking sap. Scales do not look like typical insects. They are small, immobile and have no visible legs. They vary in appearance depending on species and sex. Some look like small fish scales attached to the plant. As a result of their unusual appearance, populations can reach damaging levels before they are noticed.

On camellia, scales usually attach to leaves but some species also attach to stems. Their feeding weakens the plant. With a heavy infestation, symptoms include yellowing of the upper leaf surface, fewer and smaller blossoms, leaf drop, twig dieback and sometimes death.

Tea scale is the most serious scale insect on camellia. It attaches to the underside of leaves. Tea scale has an oblong shape with a ridge down the center parallel to the sides. It is a small scale with the female about 1/20 inch. The male is about two-thirds the size of the female. The females vary in color from dark brown or gray to nearly black. Males are white. The female lays 10 to 16 eggs, which remain protected under her body until they hatch. In one to three weeks, bright yellow immature forms called crawlers hatch from the eggs. A typical symptom of tea scale infestation is yellow splotches on the upper surface of leaves. With a large infestation, the undersides of the leaves are covered by a cottony mass.

Controls: With a light infestation, scales can be scraped off the plant and discarded. If only a few leaves are infested, hand picking and destruction of infested leaves is very effective. The best time to spray with a refined horticultural oil (Bonide All Season Spray Oil, Ferti-lome Scalecide, Green Light Horticultural Oil Spray, or Ortho Volck Oil Spray) is in spring, after the plants have finished blooming and the danger of cold weather has passed.  This will kill many adults, crawlers and eggs by smothering them. Spray two applications, 10 days apart. Spray when temperature are between 40 and 85 degrees.

Most insecticides are effective only against the crawlers. In addition, using an insecticide against scales can result in the deaths of naturally occurring enemies of scales. As such, insecticides should be avoided unless the camellia is very valuable.

Monitor the crawler emergence with sticky cards, tape wrapped around a branch, or by putting an infested shoot or leaf into a baggie and watching for crawler movement. Crawler activity often coincides with the flush of new plant growth in the spring. However, some scale species may have overlapping generations with an extended crawler emergence period, such as along the coast.

Insecticides labeled for homeowner use against tea scale crawlers include acephate (Ortho Japanese Beetle Killer), malathion (Ferti-lome Mal-A-Cide, or Hi-Yield Malathion Insect Spray), cyfluthrin (Bayer Advanced Garden Power Force Multi-Insect Killer), and carbaryl (Sevin 50WP or Ferti-lome Carbaryl Spray). As with all pesticides, read and follow all label instructions and precautions.