There are several pest problems that are associated with camellias, but few can affect the appearance of the plants as quickly as spider mites. These tiny pests are not actually insects, but are closely related to spiders and ticks. They congregate on the underside of the foliage and do their damage by sucking the cell content of the leaves. Spider mites are especially destructive during hot weather and periods of drought, but they can do much damage at just about any time during milder weather.
These pest are difficult to see with the naked eye and appear as a dust on the underside of the leaves. The top side of the foliage shows visible damage appearing like the leaves have been lightly dusted with a bronze of silver spray paint. If left untreated, the entire foliage can turn a very unsightly color very quickly.
The best chemical control that we have found is to thoroughly spray the entire plant with horticultural oil when you begin to see damage occurring. Extra attention should be made to do a thorough job of spraying under the foliage where the mites are living. The horticultural oil acts as a sufficient to kill the mites, and it is much safer on the applicator and the environment than using harsh chemicals. You may need to make more than one treatment to control this problem. You can spray with a pump up sprayer, but we prefer to use a hose end sprayer that has a greater water pressure resulting in better coverage of the horticultural oil.
Once you can get the immediate problem under control, we would recommend a regular spraying program to keep spider mites from causing damage to your plants. When using any chemical, always read the label and carefully follow all the instructions.