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How to Manage Pests

UC Pest Management Guidelines


Floriculture and Ornamental Nurseries

Shasta Daisy (Chrysanthemum maximum)

Disease Control Outlines

(Reviewed 3/09, updated 3/09)

In this Guideline:


Disease (causal agent) Symptoms Survival of pathogen and effect of environment Comments on control
Acremonium wilt
(Acremonium strictum)
Wilting, stunting, chlorosis and necrosis, often unilateral, of lower leaves. Vascular browning. Symptoms often develop with the onset of flowering. Soilborne fungus. Disease is intensified if plants are stressed by excessive soil moisture. Fungus has a wide host range, including many weeds. Plant disease‑free plants. Fumigate soil with methyl bromide‑chloropicrin combination.
Cottony rot
(Sclerotinia sclerotiorum)
Plants wilt and die. Basal stem rot. Cottony, white mycelium present in and on stems under moist conditions. Large black sclerotia form in and on stems. Fungus survives in soil as sclerotia that germinate after a cold‑dormancy period and produce airborne spores, which infect only dead or dying tissue. Direct infection from sclerotia may occur. Fungus has a wide host range. Optimum temperature for germination of fungus is 56° to 59°F and needs high soil moisture for at least 10 days. Avoid planting in infested fields or fumigate soil. Carrots, celery, and lettuce are common hosts. Treat soil with PCNB before planting. Protect plants with thiophanate‑methyl. more info *
Fasciation
(Rhodococcus fascians)
Short, swollen clumps of distorted shoots that do not elongate at the base of plants. Vigor of plant is reduced. Secondary rotting of clumps may kill plant. Bacteria survive on infected plants and debris. Bacterium has a wide host range. Spreads in water. Plant disease‑free plants. Avoid injuries to base of plant, especially when plant is wet. Control is difficult; plants may have to be discarded.
Leaf spot
(Septoria leucanthemi)
Brown, circular and irregular spots on leaves. Heavily infected leaves yellow and die. Minute black dots (pycnidia) are visible in the center of spots. Fungus survives on infected plants and debris. Spores are spread by splashing water. Pathogen needs condensed moisture to germinate and infect. Use disease‑free plants. Rotate land for 2 years. Avoid overhead irrigation and cultural operations when foliage is wet. Protect plants in rainy weather with chlorothalonil or thiophanate-methyl.
Pythium root rot
(Pythium spp.)
Plants stunted as a result of reduced root system. Small roots rotted. Soilborne pathogen. Spores spread with soil and water. Favored by excess soil moisture and poor drainage. Avoid poorly drained soils. Plant on raised beds. Reduce amount of irrigation water. Mefenoxam applied at transplanting will help get plants started. more info *
Root knot nematode
(Meloidogyne hapla)
Plants are stunted. Swellings or galls on roots. Nematodes survive in soil as eggs. Disease is usually most severe in sandy soils and in warmer climates. Preplant fumigate soil with methyl bromide‑chloropicrin or a nematicide or solarize soil.**
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Diseases
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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