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How to Manage Pests

UC Pest Management Guidelines

Floriculture and Ornamental Nurseries

Strawflower (Helichrysum bracteatum)

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
Downy mildew
(Plasmopara halstedii and Bremia lactucae)
Two distinct downy mildews infect strawflower, though symptoms are similar for both diseases: yellow foliage with downy white sporulation on the undersurface. Leaves roll downward. Tissues sometimes are killed Disease is favored by cool (59°F), wet weather. Spores (sporangia) are airborne. Chilean tarweed (Madia sativa) and other members of the family Compositae are hosts of P. halstedii. Control tarweed for some distance away if possible. Protective fungicides should be effective but few if any are labeled for strawflower. more info *
Verticillium wilt
(Verticillium dahliae)
Wilting and yellowing of lower leaves on one side of plant. Vascular discoloration. Favored by cool spring. Symptoms develop rapidly in hot weather at flowering. Fungus survives in soil for long periods as microsclerotia. Many plants are infected including weeds, crop plants, and ornamentals. Avoid fields that are known to be infested. Soil fumigation with methyl bromide-chloropicrin combination is effective. more info *
Virus or viruslike disease Symptoms Host range and natural spread Comments on control
Aster yellows
(Aster yellows phytoplasma)
Plants stunted and yellow. Frequently one‑sided. Flowers may be green. Aster yellows phytoplasma is spread by leafhoppers. A wide variety of plants including weeds are susceptible. Control weeds in and around planting. Leafhopper control may help.
* For additional information, see section on Key Diseases.



[UC Peer Reviewed]

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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