Plant Disease Management Handbook

Cause Alternaria cucumerina is a fungus that overwinters on partly decayed melon plant refuse. It also may live in soil for short periods of time. The fungus is spread in infested soil or refuse, by wind and irrigation water, and also is transmitted by seed. Weak and senescent plants are more susceptible to infection.

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Rapeseed = Canola (Brassica napus and B. rapa = B. campestris)

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Hemp (Cannabis sativa)

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Greenhouse Plants, Ornamental - Gray Mold

Image related to Candytuft (Iberis spp.)-Botrytis Blight

Botrytis has started to sporulate on the lower necrotic flower.

Jay W. Pscheidt, 2014.

Cause Both a genetic variegation and a viral infection can produce this effect. Neither seems detrimental to the plant; some propagators even desire them. There are 3, maybe 4, different viruses that have been associated with this symptom and have been provisionally named camellia ring-spot associated virus 1 through 4. (Former names may include camellia leaf yellow mottle virus or camellia infectious variegation virus). These virus particles are flexuous and filamentous.

The viral variegation produces irregular color breaks on flowers and leaves may show white or yellow blotches.

Jay W. Pscheidt, 2020.

Note the white color break on flowers and chlorosis (yellowing) of the leaves.

Photo by Jay W. Pscheidt, 1995.

Slide labeled likely Camellia yellow leaf mottle.

Oregon State University Plant Clinic image, 2010.

Cause Leaves facing the south and southwest are most likely to show sunburn. New leaves exposed to high radiation following periods of cool, cloudy weather are at high risk for injury. Newly transplanted bushes may also be of increased risk of developing sunburn. Cold clear winter weather can also be conducive to sunscald.

Symptoms Necrotic lesions on sun-exposed Camellia leaves. Brown necrotic areas may have grayish centers and/or with yellowish borders.

Lower leaves burned when exposed to strong , late afternoon sun. Newer leaves that developed later are fine.

Jay W. Pscheidt, 2010.

Cause Saprophytic fungi that live on the excrement of cottony camellia scale and soft brown scale, common camellia insect pests. The fungus Atichia glomerulosa (sexual Seuratia millardetii) called false sooty mold has been found in Washington. This fungus lacks hyphae, is not parasitic and does not seem to be associated with scale insects.