How to Manage Pests

UC Pest Management Guidelines

Turfgrass

Seed Rot and Damping Off

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

(Reviewed 9/09, updated 9/09, pesticides updated 12/16)

In this Guideline:


DESCRIPTION OF THE DISEASE

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 oflocations 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 Amount to use Ag Use
REI‡
NonAg Use
PHI‡
(Example trade name)   (hours) (days)

UPDATED: 12/16
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide's properties, efficacy, application timing, and information relating to resistance management, honey bees (PDF), and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. CAPTAN
  (Captan 4L or 50 WP) Label rates See label Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
 
B. FLUDIOXINIL
  (Medallion) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)
  COMMENTS: Effective against Rhizoctonia and Fusarium.
 
C. MANCOZEB
  (Fore 80WP, Dithane M-45) Label rates 24 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)
  COMMENTS: Effective against Pythium. Dithane M-45 registered for use on sod farms only.
 
D. MEFENOXAM
  (Apron XL) Label Rates 48
  MODE-OF-ACTION GROUP NAME (NUMBER1): Phenylamide (4)
  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. 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 (REI) 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.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T

Diseases

A. Downer, UC Cooperative Extension, Ventura County
M. A. Harivandi, UC Cooperative Extension, Alameda County

Acknowledgment for contributions to Diseases:
F. Wong, Plant Pathology, UC Riverside
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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