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How to Manage Pests

UC Pest Management Guidelines

Sparse growth of turf due to seedling damping off caused by Pythium spp., Rhizoctonia spp., Fusarium spp., and/or Helminthosporium spp.


Seed Rot and Damping Off

Pathogens: Pythium spp., Rhizoctonia spp., Fusarium spp.

(Reviewed 9/09, updated 9/09)

In this Guideline:


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.


All grasses are susceptible to these diseases.


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.


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 Example trade names Ag Use
NonAg Use
(trade name)   (hours) (hours)

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When choosing a fungicide, consider general properties as well as information relating to environmental impact.
A. CAPTAN Captan  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4) 4 days until dry
B. FLUDIOXINIL Medallion  
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12) 12 until dry
  COMMENTS: Effective against Rhizoctonia and Fusarium.
C. MANCOZEB Fore, Dithane M-45  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M3) 24 until dry
  COMMENTS: Effective against Pythium. Dithane M-45 registered for use on sod farms only.
D. MEFENOXAM Subdue Maxx, Apron  
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4) 48 Subdue Maxx: until dry
Apron: —
  COMMENTS: Effective against Pythium; not effective against Rhizoctonia and Fusarium.
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.
Indicates use is not listed on label.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda County
Acknowledgment for contributions to Diseases:
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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