How to Manage Pests

UC Pest Management Guidelines

SUSCEPTIBLE TURFGRASSES
Bermudagrass is susceptible to spring dead spot.

CONDITIONS FAVORING DISEASE
The pathogen survives in debris (old thatch and roots) as fungal threads and sclerotia, which are tiny, hard, often dark, resting bodies. Spring dead spot is spread by sclerotia and infected plant parts, as well as through infested sod. Initial infections of new tissue begin in late summer or fall when air temperatures range between 70° to 75°F. When the bermudagrass goes into dormancy (daily air temperatures of 50° to 60°F or lower), the fungus continues to colonize and kill the affected tissue. Damage to the affected plants is usually only visible when the bermudagrass emerges from dormancy.

MANAGEMENT
The focus of a spring dead spot management program should be exclusion of the pathogen from new plantings and promoting strong, heathly turf and root systems that can tolerate and recover quickly from the damage caused by the fungus. Proper irrigation and fertilization are important in the management of this disease. Spring dead spot is difficult to manage with fungicides.

Cultural Control
Establish new turf plantings with clean sod from areas where spring dead spot has not been a problem. Irrigate according to evapotranspiration needs of the turfgrass. Dead grass can be raked out and replanted with new bermudagrass seed or stolons; alternately, bermudagrass can be overseeded with ryegrass in fall or winter to hide disease symptoms in spring.

Thick thatch and low mowing heights favor the development of the disease. Manage thatch and keep it less than 0.5 inches thick with regular dethatching and aerification. Provide adequate irrigation based on evapotranspiration needs to promote vigorous growth during summer months and reduce drought stress damage. Raise mowing height in late summer or early fall to reduce pre-dormancy stress.

Maintain adequate levels of potassium in the soil and apply potassium fertilizers in fall to promote winter hardiness. Use adequate nitrogen fertilization programs in spring and summer, but minimize nitrogen applications in late summer and fall. Late summer and fall applications may contribute to disease severity because the added nitrogen promotes the growth of leaves at the expense of roots and may delay the bermudagrass from entering dormancy, resulting in both a reduction in cold hardiness and carbohydrate reserves. Loss of carbohydrate reserves is detrimental to plants when they are emerging from dormancy in spring. Use ammonium-based nitrogen sources versus nitrate- or urea-based fertilizers. Maintaining a low soil pH (5.2 to 5.3) appears to reduce the severity of the disease.

Treatment Decisions
Once established, spring dead spot is a difficult disease to control with fungicides. Best results are usually seen when a combination of cultural and chemical control methods is used. Make one or two fungicide applications beginning in the late summer or early fall using enough water volume to get the fungicide into the root zone.

Common name		Chemical class
Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.
A.	AZOXYSTROBIN	QoI (strobilurins)
B.	FENARIMOL	DMI
	COMMENTS: A systemic fungicide that is very effective against spring dead spot. Apply in Sept.
C.	MYCLOBUTANIL	DMI
D.	PROPICONAZOLE	DMI

PUBLICATION

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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