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How to Manage Pests
UC Pest Management Guidelines
Turfgrass
Seed Rot and Damping Off
Pathogens: Pythium spp., Rhizoctonia spp.,
Fusarium spp.
(Reviewed 6/03,
updated 6/03)
In this Guideline:
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DESCRIPTION OF THE DISEASES
Seeds affected by seed rot are rather dry and do not germinate. Damping off may
affect seedlings at either the pre- or postemergence stage. The hypocotyl area
of seedlings is particularly susceptible. Seedlings appear water soaked, then
blacken, shrivel, and turn brown with stunted growth.
SUSCEPTIBLE TURFGRASSES
All grasses are susceptible to these diseases.
CONDITIONS FAVORING DISEASE
Seed rot and damping off can occur at a wide range of temperatures (50° to
100°F) but are more common at temperatures above 70°F. Seed rot and
damping off are favored by excessive moisture and by sowing seeds of low
viability above the recommended rates, especially during periods unfavorable
for seed germination and growth.
MANAGEMENT
Before planting a site with turfgrass, make sure the soil is adequately aerated
and there is good drainage. Sow fresh, healthy seed at recommended rates and
seasons. Do not seed cool-season turfgrass during hot weather. As the turfgrass
grows, avoid overwatering. Seeds should be treated with fungicide before they
are planted and again at first evidence of symptoms of damping off.
Treatment Decisions
Mancozeb, captan, thiram and mefenoxam are common fungicide seed treatments.
Resistance has developed to mefenoxam for Pythium in a number of
locations in the United States. Practice resistance management by alternating
the use of fungicides with a different chemistry. In cases where mefenoxam no
longer provides control, switch to a fungicide in a different chemical class.
| Common name |
Chemical class |
Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.
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| A. |
CAPTAN |
Pthalamide (multi-site) |
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| B. |
FLUDIOXINIL |
Phenylamide |
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COMMENTS: Effective against Rhizoctonia and Fusarium. |
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| C. |
MANCOZEB |
EDBC (multi-site) |
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COMMENTS: Effective against Pythium. |
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| D. |
MEFENOXAM |
Phenylamide |
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COMMENTS: Effective against Pythium; not effective
against Rhizoctonia and Fusarium. |
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UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Diseases
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda Co.
J. Hartin, UC Cooperative Extension, San Bernardino Co.
Acknowledgment for contributions to the disease section:
M. E. Grebus, Plant Pathology, UC Davis
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