Management Update Archive

Signs and symptoms of anthracnose have been observed on putting greens in southern New England this June. Anthracnose is caused by Colletotrichum cereale and is considered to be an indicator of turf stress.

The fungus survives as a saprophyte in plant debris or as a pathogen in infected tissue. Under the proper environmental conditions, it produces abundant spores that are spread by splashing rain, equipment, and foot traffic. Optimal conditions for infection are at least 12 hours of leaf wetness and temperatures above 59°F. There is a latent period of approximately 7-10 days between infection and symptom development. Disease develops in turf growing under low fertility, temperature stress, drought, or any other factors that cause turf stress.

C. cereale commonly causes a foliar blight but may cause basal rot if the fungus infects the crowns and/or stolons. The basal rot form of the disease is most common in the cool, wet weather of spring, while foliar blight is more often seen in periods of summer stress. Symptoms typically appear as diffuse areas of yellow or orange discoloration and turf thinning. Leaf blades die from the tip down. The disease is most severe in areas of poor drainage, heavy traffic, and soil compaction.

Annual bluegrass is most commonly affected, but some strains of C. cereale will cause disease on bentgrass. Anthracnose can become a chronic problem on greens and can be difficult to control. It is a disease of low-cut, highly managed turf and is not normally an issue on lawns.

Cultural Management:

• Increase mowing height. An increase of as little as 0.020 inch can have a significant impact on disease severity. Green speed can be maintained by rolling 3-4 times per week. Use walk behind mowers if possible.
• Irrigate greens as needed to avoid drought stress. Alleviate any other sources of stress to encourage turf recovery. Divert traffic from affected areas and avoid grooming practices such as double-cutting and brushing until turf recovers.
• Spring topdressing (4-8 cubic ft/ 1000 ft² biweekly) can be very effective if summer topdressing is minimal. Light topdressing (1 cubic ft/ 1000 ft² biweekly) throughout the summer has also been associated with an overall improvement in anthracnose control in mid to late summer.
• If seeding new greens, consider bentgrass cultivars with moderate resistance to anthracnose and avoid the most susceptible cultivars (Providence, Pennlinks II, Penncross, Seaside II, and Brighton). Turf cultivars with superior resistance to summer stress may be less susceptible to foliar anthracnose.
• Nitrogen fertility can influence anthracnose severity. Nitrogen application in spring is generally more effective than in fall for anthracnose control. Nitrogen applied at rates of 1-2lbs/1000 ft² in early spring reduces disease severity, particularly on greens with a history of anthracnose. With higher rates, slow-release N should be included. Potassium nitrate is generally the most effective form for anthracnose management; avoid ammonium sulfate. In late spring and throughout the summer, nitrogen should be applied to greens biweekly at a rate of 0.1-0.2 lbs./1000ft² to encourage the growth and spread of healthy turfgrass.
• Ensure adequate potassium levels: inadequate potassium nutrition predisposes turf to anthracnose.
• Maintain a soil pH of 6 or above.
• Implementation of good cultural practices will decrease disease severity and often improves fungicide efficacy.

Chemical Management: Preventive spray programs are more effective than curative programs. Tank mixing or use of combination products is recommended. A protectant mixed with a systemic fungicide is perhaps the most common recommendation. QoI and DMI fungicides may have some curative activity, but there is a high risk of resistance development with these products. Many strains of C. cereale are resistant to QoIs and benzimidazoles. SDHI fungicides carry a moderate to high risk of resistance development. Proper rotation of FRAC groups is crucial for the prevention of resistance development. For basal rot anthracnose, water in lightly (< 0.1”) and let dry.

For more information on specific fungicides, please see the following:

• Chemical Control of Turfgrass Diseases
• Anthracnose in Turf
• UMass Extension Professional Turf IPM Guide

Always read and follow the label. Ensure that products are registered for turf in your state before using.

Submitted by: Dr. Angela Madeiras, Extension Educator and Diagnostician, UMass Extension Plant Diagnostic Lab