Plant Health Problems
Diseases caused by Physiological/Environmental Factors:
Bud drop, physiological.
Buds drop prematurely before opening or newly expanding buds and flower petals develop brown edges. This condition is common and associated with many factors including overwatering, insufficient light, high temperatures, and overfertilization.
Bud drop can be minimized by careful attention to cultural care and uniform watering.
Chlorosis, overwatering, nutrient deficiency.
Leaves develop a yellow or chlorotic appearance. This can be due to root damage from overwatering or from nutrient deficiencies in the potting medium.
This problem can be minimized by careful attention to cultural care.
Soluble salt injury, excessive fertilization and soluble salt accumulations.
Camellias are particularly sensitive to high soluble salt levels in potting media. Root injury caused by excessive levels of fertilizer in the potting mix results in a general decline or collapse of the plant. Symptoms are similar to those caused by root rot so soil analyses for soluble salt levels are often necessary for correct diagnosis. An indication of high soluble salts is the presence of white, crystalline deposits on the rim or outer surface of the pot or on the surface of the potting mix.
Soluble salts can sometimes be leached from the potting mix by running a stream of water through the pot for approximately 20 minutes. However, when salt levels are excessive, the plant can be repotted into fresh, sterile potting mix and a clean pot. It is also important to avoid excessive use of fertilizer, especially during periods of slow growth.
Camellia scale, Lepidosaphes camelliae.
This yellowish brown scale with white margins, a distinct groove and nearly parallel sides, infests many different plants in the greenhouse, including camellia. Malathion, horticultural oil or insecticidal soap, which are among the compounds registered for control of this pest in Connecticut, sprayed to control scale crawlers have been effective. Consult the labels for dosage rates and safety precautions.
Fuller rose beetle, Asynonychus godmani.
Roses and many other plants in greenhouses as well as outdoors are sometimes injured by Fuller rose beetle which feeds on the leaves at night and rests in the leaves or in protected places during the day. This is a brown weevil marked with patches of gray scales on fused wing covers. Only females exist. It varies in length from 1/4" to 3/8" (7-9 mm). The eggs are laid under the edges of bark near the ground or directly on the ground and can be found throughout the season. The white legless grubs live in the soil and chew upon the roots of various plants. At maturity, they measure about 1/2" (10-12 mm). This weevil overwinters as a pupa near the soil surface or as an adult in a protected spot. Adults do the most damage. Control treatments are rarely needed. When the infestation is light, handpicking the insects is a possibility.
Mealybugs, Planococcus citri.
White cottony masses appear on leaf surfaces, in leaf axils and sheaths. These insects damage plants by sucking plant sap. Among the compounds registered for control of this pest in Connecticut are insecticidal soap, ultrafine horticultural oil or resmethrin. These products are most effective against crawlers. Because of overlapping life stages in a home environment, multiple applications will be needed to control this pest. Spray needs to contact the insect. Consult the labels for dosage rates and safety precautions. On plants used as annuals outdoors, insecticidal soap, ultra-fine horticultural oil as well as malathion, which are among the compounds registered for use against this pest in Connecticut, can be used to control this insect if needed. Imidacloprid, applied as a systemic to be taken up by the roots, will also provide season-long control. Consult the label for dosage rates and safety precautions. The mealybug destroyer ladybeetle, Cryptolaemus montrouzieri, is quite effective against citrus mealybug, but is ineffective against longtailed mealybugs. Their long tail filaments and the lack of cottony ovisacs readily distinguish longtailed mealybugs, Pseudococcus longispinus.
Soft scale, Coccus hesperidum.
This soft scale is very thin, oval, and semi-transparent. It infests many different greenhouse plants including camellias. Any control sprays may need to be repeated if only the crawler stage is controlled. The remedy is to spray with insecticidal soap or malathion, which are among the compounds registered for control of this pest in Connecticut, repeating as necessary. Do not use malathion indoors. Imidacloprid is very effective as a systemic that is taken up by the roots. Consult the labels for dosage rates and safety precautions.