ANTHRACNOSE

anthracnose acervuli	Characteristic	Description
	Host Grass Species	creeping bentgrass, annual bluegrass
	Month(s) with symptoms	May to September
	Stand Symptoms	irregular distribution across turf stand or patches (4 to 12 inches)
	Foliar Symptoms - Location/Shape	dieback from leaf tip, blighting of entire leaves
	Foliar Symptoms - Color	yellow, orange, tan, red
	Root/Crown Symptoms	none or roots, stolons, rhizomes, and/or crowns dark brown or black
	Fungal Signs	acervuli with setae

 

Note: Still not sure if this is the right disease? The Turfgrass Disease Identification program may be helpful. Or consult the experts at the Turf Diagnostics Lab. Check the TurfFiles glossary for definitions of unfamiliar terms.

FACTORS AFFECTING DISEASE DEVELOPMENT

Anthracnose can occur virtually year-round in North Carolina and many other parts of the country. In creeping bentgrass putting greens, anthracnose basal rot is most active during hot weather in the summer, whereas the foliar blight is most common during cool and cloudy conditions. The opposite is true on annual bluegrass, with the basal rot being most severe in cool, cloudy weather and the foliar blight more common during hot, dry weather.

Anthracnose diseases are stress-induced. Physiological stress from any source greatly encourages the development and spread of the disease. In golf course putting greens, the most common culprits are close mowing, drought stress, low fertility, excessive traffic, poor soil drainage, or excessive thatch/organic matter accumulations.

Because of its sensitivity to stress, annual bluegrass is much more susceptible to anthracnose than creeping bentgrass, but creeping bentgrass varieties vary tremendously in their susceptibility to anthracnose as well. Older varieties, such as Penncross, Pennlinks, Dominant, Dominant Plus, L-93, and Crenshaw are susceptible to anthracnose, whereas the disease is rarely observed on modern varieties such as the Penn A and G series.

CULTURAL CONTROL

Because annual bluegrass is most susceptible to anthracnose, preventing this grassy weed from encroaching into putting greens is an effective way to manage anthracnose. Conversion of putting greens to newer, resistant varieties of creeping bentgrass will eliminate the problem in most circumstances.

Avoiding or alleviating physiological stress is another effective way to manage anthracnose. Raising mowing heights prior to and during periods of disease activity have been shown to reduce anthracnose development. Recent research at Rutgers University demonstrated that anthracnose severity was greatest in annual bluegrass mowed at 0.110”, less at 0.125”, and the least disease was observed at 0.150”.  Golf course superintendents should employ growth regulators and lightweight rollers to increase putting speeds in lieu of low mowing heights. When using sidewinder-type rollers, care must be taken to prevent scuffing and abrasion at the end of each pass, as this injury may encourage anthracnose activity.

Adequate fertilization and irrigation are also essential to anthracnose management. Deficiencies of any essential plant nutrient will slow turf growth and increase anthracnose development. Tissue samples should analyzed for nutrient content on a regular basis to ensure that all nutrients are present in adequate amounts. Irrigation should be applied frequently enough to prevent severe wilt and drought stress during the day.

Regular aerification and topdressing of putting greens is essential to preventing severe anthracnose problems. As a general rule of thumb, 15% to 20% of the putting green surface area should be impacted by hollow-tine aerification annually, and 5000 lbs/1000 ft² of topdressing should be applied each year. Hollow-tine aeration should be performed during cool weather conditions when the turf is growing optimally. Solid-tining or spiking is recommended during stressful conditions to provide temporary channels for air and water movement through the soil profile. Topdressing applications during the summer should be light enough to water-in, as the wounding caused by dragging or brooming operations can spread the disease.

CHEMICAL CONTROL

Successful control of anthracnose with fungicides requires a preventative approach. Although the precise timing of infection is unknown, the anthracnose pathogen likely infects turf plants long before the symptoms appear. Where anthracnose has been a persistent problem, a preventative fungicide program should be in place throughout the growing season. In less severely affected sites, a preventative program should be implemented prior to the onset of summer stress and during extended periods of cool, cloudy weather.

The anthracnose pathogen can become resistant to certain fungicides very quickly. In a recent survey of C. cereale populations in North Carolina, all isolates were resistant to the benzimidazole fungicides, and most exhibited some level of resistance to the QoIs. Research at the University of California-Riverside has shown that DMI resistance is developing slowly in anthracnose populations as well. Golf course superintendents should tank-mix and rotate fungicide classes regularly to slow the development of resistance and reduce their reliance on a single fungicide chemistry.

© North Carolina State University. This information sheet was prepared by Lane P. Tredway, Gail G. Wilkerson, Bridget R. Lassiter, Jenifer J. Reynolds, and Gregory S. Buol. Departments of Plant Pathology and Crop Science, College of Agriculture & Life Sciences, North Carolina State University. Prepared March 23, 2009. Available on-line at www.turffiles.ncsu.edu. This publication was made possible through a grant provided by the Center for Turfgrass Environmental Research & Education (CENTERE) whose purpose is to support worthwhile projects that will benefit both the private sector and the public, and protect the environment.