How to Manage Pests
UC Pest Management Guidelines
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.
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.
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.
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.
UC IPM Pest Management Guidelines: Turfgrass
A. Downer, UC Cooperative Extension, Ventura 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