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Introduction to Camellia Deseases.
This is a very personal view based on a limited experience of camellia culture. Professional writers with more experience are invited to correct me.Most disorders of camellia plants are of physiologic nature and can be cured or reduced by changing cultural conditions. There are few exceptions where great care and chemical treatment is necessary. The exceptions are, to my limited knowledge, petal blight and weevil attack, but there might be others, and don't hesitate to tell me.
Camellias in pots are more subject of attacks compared to those in open ground, and young plants are more indangered than established ones. Scale insects and, on young shoots, aphids may become a problem. Very close inspection of the plants is necessary on a regular basis, and proper counteraction with cleaning solution (below) is in most cases sufficient to control a possible infection.
Amateur growers should avoid the use of toxic chemicals, instead use soap, water and denaturated ethyl alcohol ( the type used in spirit lamps ). The following cleaning solution is quite useful: 1 part alcohol, 3 parts water and about 2-3 tablespoons of liquid soap of any kind as detergent. The solution is harmless to the plant even if sprayed in completely, but aphids don't like it, and scales are reduced. Further, you can wipe off the scales quite easily with a sponge, thereby cleaning the leaves from sooty molds. Also plastics and greenhouse parts can be cleaned by this general solution. Scale insects can also be wiped of by a cotton stick dipped into pure alcohol, there is no damage to leaves and stems. Only if the pest is not controlled by these actions, use insecticides.
Do not use fungicides. In most cases, where fungus infection is supposed, the proper action is to repot, since very likely the reason is inproper soil condition, or cultural mistreatment. Camellias have a long dormancy period of about three quarters of the year, they do not immediately indicate mistreatment like dry roots or other damage, and six to nine months later twigs dye back or leaves wilt. With this delay, the original cause is forgotten and not related to the disorder, and fungus is suspected. Yellow leaves result most oftenly from a soil with too large water retention and over watering. Since watering habit can be controlled only after years of experience, change the soil to insure better draining. The best advice in any unclear camellia disorder is to repot.
Commercial growers cannot give their plants this intensive care, and they depend on insecticides and fungicides, but they have the proper equipment and knowledge to use them adequately.
P.S. We try to establish a diagnostic guide for camellia deseases and disorders. Be patient, this takes time. --K.P.
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