How to Manage Pests
UC Pest Management Guidelines
Floriculture and Ornamental Nurseries
Strawflower (Helichrysum bracteatum)
Disease Control Outlines
In this Guideline:
|Disease (causal agent)
||Survival of pathogen and effect of environment
||Comments on control
(Plasmopara halstedii and Bremia
|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.
||Control tarweed for some distance
away if possible. Protective fungicides should be effective but few if any
are labeled for strawflower. more info *
|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
||Host range and natural spread
||Comments on control
(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 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
Top of page