Camellias that are well maintained and nurtured are less susceptible to disease. Many problems can be prevented or corrected with correct identification of the problem.
Top photo: Leaf fungus caused by damage to the leaf and a pathogen enteres for forms the familiar rings. Remove leaves affected and treat with a fungicide.
Algae Leaf Spot
A common disorder especially in the deep south where the winters are mild and humid. It normally affects older leaves that drop and are replaced my new leaves. If severe, you can treat with a copper fungicide for prevention, but not for a cure. It is usually not life threatening to the plant, but it can be unsightly.
CAMELLIA PETAL BLIGHT
Photo Courtesy of The American Camellia Society
Caused by the fungi Ciborinia camelliae, each year in early spring, open blooms are infected with the fungi. The flower turns brown and falls to the ground where the fungi lay dormant for another season. When the weather warms these fungi rise in the air, attach to the blooms and the cycle begins again. Billions of spores can be released if there are a lot of camellias in the garden making control difficult. In the nursery however, it is much easier to control as blooms are often cleaned up before the next season blooms.
CAMELLIA CANKER AND DIEBACK
Photo Courtesy of The American Camellia Society
Caused by the fungus Glomerella cingulata, this can cause significant damage or death to camellias. It is most common in the deep south where weather is hot and humid. The disease can affect all camellias, but can be especially damaging on Camellia sasanqua and Camellia reticulata. The fungal disease enteres the plant through an open wound, which can be as simple as the opening of the bark where a leaf fell off, or a cut, scrape or tear from animals (cats) or lawn equipment. The disease quickly destroys surrounding tissue, often seen as a browning or drying in the bark. Destroying this tissue cuts off water and nutrients to the plant above the infected area. This causes this part of the plant to wither and die. With Dieback disease, leaves dry up but stay on the plant, they do not fall off. At the point of damage, the trunk or branch can be swollen or cracked which is the indicator for dieback. Prevention is usually the best bet – using a fungicide when the plant is damaged can help somewhat. Removing infected branches keeps the disease from spreading to other open wounds.
FALSE DIEBACK-CANKER DIAGNOSIS: Many growers quickly blame dieback/canker for these symptoms without fully examining the plant for other causes. For example, Twig Borers and other boring insects can cause the same results as dieback/canker where limbs or twigs are dying, but leaves hanging on. On close examination you may see small pinholes in the bark below where the damage originates. Insect damage can be controlled. You just have to recognize the type of problem so you can know how to fix it.
Cold Damage can also cause bark to split and the limbs or twigs to die. This may not show up right away and can take months for it to show up.
Leafgall of Camellia happens in the spring of each year and is thought to be caused by a fungal pathogen. It does not harm the camellia, but it can be quite unsightly. Remove any Gall and discard it to prevent spread to other camellias.
Symptoms of scab are rather varied; however, it usually appears first as a tiny, water-soaked, and often raised area on the underside of the leaf. These spots enlarge and may become corky, brown in color, and of irregular size and shape. The condition may also appear on the top of the leaf.
Scab is a physiological condition associated with excess moisture or fluctuations of moisture from too high to too low. There is no biological agent associated with this condition and chemical sprays are ineffective. It is believed that improvement of drainage and growing conditions are the best possible control
Sunburn or sunscald appears as yellowish or bronzed areas on the upper side of the leaves with severely affected areas turning brown. These brown areas nearly always are interveinal and appear in the center of the leaves as opposed to salt injury which appears at the leaf margins. It is especially seen on plants with virus variegation in the foliage or when plants are moved from shade to sunshine. Some varieties are more susceptible than others
Salt injury is characterized by browning and death of the leaf tissue beginning at the margins and progressing inward. Most often the injury will appear first on older leaves
Too high a concentration of salts in the soil or in the irrigation water or the use of heavy doses of fertilizer coupled with inadequate irrigation will cause this condition. This problem will develop rapidly in container grown plants. To prevent this condition, camellias should be planted in a medium with good drainage. An occasional heavy irrigation will help to leach away the excess salts
Camellias that are exposed to very sudden or severe freezes or cold winds can develop cold damage. If severe weather occurs, cover or protect your camellias to prevent or minimize damage. Always make sure your camellias are well hydrated before a cold snap. Wind is more damaging to plants that the actual cold.