BENTGRASS DEADSPOT Ophiosphaerella agrostis   F A C T S H E E T

Introduction

Bentgrass Deadspot is a fairly new disease caused by a fungus, Ophiosphaerella agrostis. The disease first appeared in Illinois in 1997. It moved quickly to other states, showing up in Maryland, Virginia, Pennsylvania, and Ohio in the early part of 1998 and in Georgia, Massachusetts, Missouri, North Carolina, South Carolina, and Texas by the end of 1998. It was reported in New Jersey in 1999. The disease appears to be more severe on newly established golf course greens under 4 years of age.

Symptoms

The disease is commonly misdiagnosed due to the similar symptoms produced by a number of other causal agents. Spots may be similar and easily confused with Dollar Spot, but Bentgrass Deadspot patches rarely coalesce. Symptoms may be similar to Copper Spot, Dollar Spot, Pink Snow Mold, Black Cutworm damage and ball mark injury.

Initial symptoms appear as small reddish spots about 1-2 cm in diameter. Spots gradually enlarge to a maximum of approximately 6 cm and have a characteristic tan center with a reddish-brown margin (Fig. 1). Open, exposed areas also appear to be affected more severely.

Figure 1: Symptoms of Bentgrass Deadspot. (provided by Dr. Peter Dernoeden, University of Maryland) Figure 2: Reproductive structures known as pseudothecia. (provided by Dr. Peter Dernoeden, University of Maryland)

As far as is known at this point, all cultivars of Bentgrass appear to be susceptible to infection by this pathogen.

Disease Cycle

The fungus invades the roots and crowns of susceptible species and affects the plants ability to transport water. Wilting occurs as a result of severe infection, especially during the heat of the summer.

Reproductive structures known as pseudothecia (Fig. 2) may be found in infected leaf tissues and in dead tissues. These structures are black, flask shaped, and embedded in the plant tissue. They release spores that cause new infections. Symptoms are more severe in hot and dry weather, but the fungus can remain active until a hard frost.

Management Strategies

There are no known resistant cultivars of Bentgrass available. Raising cutting heights when mowing may help reduce the severity of the disease. It has been documented that the closer the cutting height, the slower the recovery time. Increasing the nitrogen level may encourage faster recovery.

If needed, applications of fungicides may be applied on a 7-10 day interval. Some products containing the active ingredient thiophanate-methyl appear to successfully control the pathogen. Before purchasing, be sure the product is labelled for the intended use, and follow directions on the label. This disease is not yet known to be a problem on residential lawns.

Created, KLS, 4/01; Updated, SLJ, 1/07

This publication contains pesticide recommendations. Changes in pesticide regulations occur constantly, some materials mentioned may no longer be available, and some uses may no longer be legal. All pesticides distributed, sold, and/or applied in New York State must be registered with the New York State Department of Environmental Conservation (DEC). Questions concerning the legality and/or registration status for pesticide use in New York State should be directed to the appropriate Cornell Cooperative Extension Specialist or your regional DEC office. READ THE LABEL BEFORE APPLYING ANY PESTICIDE. __________________________________________________________________________________
The Plant Disease Diagnostic Clinic at Cornell University is located at 334 Plant Science Building, Ithaca, NY, 14853. Phone: 607-255-7850, Fax: 607-255-4471, Email: kls13@cornell.edu or slj2@cornell.edu