How to Manage Pests
UC Pest Management Guidelines
Floriculture and Ornamental Nurseries
Camellia (Camellia spp.)
Disease Control Outlines
In this Guideline:
|Disease (causal agent)
||Survival of pathogen and effect of environment
||Comments on control
|Wilting and dying of branches.
Leaves darken and often remain attached. Branch is girdled by fungus that enters through injuries, including leaf scars.
||Found in warmer areas of
California. Favored by wet, warm conditions, weakened plants, and injuries.
Fungus spores (conidia) are spread by splashing water. Fungus has a wide host range.
||Prune diseased tissues and protect wounds with a fungicide such as captan. Avoid overwatering.
||Flowers have dry rot with accented
veins. Only petal tissues are infected. First symptoms are small tan or brown
necrotic spots in the center of the flower that enlarge and move rapidly to
the base of flower. Rotted flowers are heavy and easily fall to ground. The
fungus continues to develop, forming sclerotia in the calyxes of infected flowers.
||Sclerotia survive on or in soil
and germinate for several years producing fruiting bodies (apothecia) that discharge spores (ascospores) forcibly into the air.
||Where practical, pick up all
blossoms because fallen blossoms either may be infected or may become
infected while on the ground. Prevent sclerotia from germinating by spraying
ground with PCNB annually. Thiophanate-methyl will protect petals from
infection but sprays must be applied frequently as new flowers open. Mulches 4 inches or more deep will help prevent apothecia from reaching the surface.
||Necrotic, brown spots. Rot does
not move to the base of the flower as rapidly as the flower blight fungus. Woolly gray fungus spores form on decayed blossoms under high humidity.
||Favored by cool wet weather. Spores are airborne. Fungus survives on and in old flowers.
||Avoid overhead irrigation. Clean
up plant debris, especially floral tissues. Protect flowers with a fungicide
effective against Botrytis such as fenhexamid. more info *
|Sudden Oak Death1(Phytophthora
||Leaf lesions that vary in size
from 0.2 inches to covering nearly half the leaf. Lesions primarily at leaf
tip or edge; can be surrounded by diffuse margins or thick black zone line.
Infected leaves drop prematurely and lower part of plant can defoliate. Symptoms may be confused with leaf scorch in areas of high heat/sun.
||Spore structures commonly form on
leaf surfaces of susceptible leaves and twigs following prolonged wetting.
They are moved in contaminated soil, from plant to plant via windblown rain, or by direct contact of infected leaves.
||Monitor incoming stock and areas
surrounding the nursery for symptoms, follow good cultural and sanitation
practices, and use preventive treatments before environmental conditions favor development of the pathogen.*
|Phytophthora root rot
||Plants stunted and low in vigor.
Foliage yellows, plant wilts and dies. Roots rotted. When plants collapse,
the stem is girdled at or below the soil line. Phythopthora cinnamoni is often involved but other species also infect camellias.
||Phytophthora spp. survive in soil as resting spores. They are
common in stream and ditch water. Infective spores (zoospores) swim very
short distances in soil water. Disease is favored by poor drainage, long wet periods, and standing water.
||Heat or chemically treat
propagation and growing media. Drench plants on a preventative basis with
mefenoxam. more info *
|Camellias are also
susceptible to several viruses and viroids such as color
break virus and golden ring spot complex.*
|* For additional information, see section on Key Diseases.
|1 Popular camellia cultivars where P. ramorum was isolated from nursery stock on two or more
occasions: C. japonica 'Bob
Hope',C. japonica 'Mrs.
Charles Cobb', C. japonica 'Daikagura' Var. C. japonica 'Debutante', C. japonica''Elegans Splendor', C. japonica 'Glen 40', C. japonica 'Kumasaka', C. japonica 'Kramer's Supreme', C. japonica 'Mathotiana Supreme', C. japonica 'Nuccio's Gem', C. japonica 'Nuccio's Pearl', C. japonica 'Silver Waves', C. japonica 'Shiro Chan', C. japonica 'Tom Knudsen', C. oleifera 'Winter's Fire', C. sasanqua 'Apple Blossom', C. sasanqua 'Cleopatra', C. sasanqua 'Hana Jiman', C. sasanqua 'Jean May', C. sasanqua 'Kanjiro', C. sasanqua 'Setsugekka', C. sasanqua 'Yuletide'
UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
S. T. Koike, UC Cooperative Extension Monterey County
C. A. Wilen, UC IPM Program, UC Cooperative Extension San Diego County
Acknowledgment for contributions to Diseases:
R. D. Raabe, (emeritus) Environmental Science, Policy, and Management (ESPM), UC Berkeley
A. H. McCain, (emeritus) Environmental Science, Policy, and Management (ESPM), UC Berkeley
M. E. Grebus, Plant Pathology, UC Riverside
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