Like a toxic concoction in a boiling cauldron, potential trouble is brewing in some parts of the country due to recent weather patterns.
With summer heat on the horizon and much of the country experiencing abnormally wet spring conditions, the threat of anthracnose is very real.
Caused by the fungal pathogen Colletotrichum cereale, anthracnose is a stress-induced disease found on annual bluegrass and creeping bentgrass putting greens. The pathogen overwinters in a state of dormancy waiting for the right time to emerge, which can be: through winter under wet, mild conditions; during periods of extended overcast conditions in late spring; under hot, humid summer conditions.
Annual bluegrass is especially susceptible, although it can be found in creeping bentgrass, as well. According to the University of Massachusetts, anthracnose also can be found in Kentucky bluegrass, fine-leaf fescues, perennial ryegrass and Bermudagrass
According to research published at Penn State, symptoms can vary depending on when the disease presents, but often first appears as yellowing turf in irregular patterns that range in size from an inch or two in diameter to more than a foot.
Many parts of the country are experiencing conditions that could be right to promote anthracnose. Pittsburgh, home to this year's U.S. Open has received nearly 20 inches of preciptiation through June 18, which is nearly double the historic average, according to the National Weather Service. The Washington, D.C., area has received a similar amount of precipitation this year.
As summer begins June 20, emperatures in the Mid-Atlantic region are climbing. Daily high temperatures in Pittsburgh are predicted to range from the low to mid-90s for the first full week of summer. Similarly, temperatures in Washington already have reached the low 90s and are expected to reach triple digits next week.
The pathogen may cause a foliar blight or a rot of crowns, stolons and roots, according to research at the University of Massachusetts.
Foliar blight occurs when leaf blades and sheaths become infected. Symptoms are most prominent during the summer stress period and include yellow to reddish brown discoloration of leaves and thinning of the turf as the plant leaves die from the tip down.
Root and crown infections result in a basal rot. This phase produces symptoms in yellowish-brown to reddish-brown patches that can be several feet in size. Basal rot happens when the crown becomes infected and rotting, and it is difficult to suppress or control. A high organic-matter content in the root zone of a sand-based green can hold excessive amounts of moisture and that promotes infection and further complicates control, according to research at the University of Kentucky.
Since basal rot anthracnose can be devastating, prevention of the disease is worth far more than a pound of cure.
According to Penn State, anthracnose can problematic in areas with poor drainage, compaction and persistant wetness at the surface, so any practice that solves such conditions, including aeration, redirecting traffic, reduced watering and tree management can reduce severity of the disease.
Nitrogen fertility is the most important factor in managing anthracnose in annual bluegrass putting. Light, frequent applications of nitrogen fertilizer can reduce disease severity and promote in some areas depending on severity of infection. Other practices that might help reduce the severity of anthracnose include avoiding scalping of turf, light and frequent topdressing, lightweight rolling with smooth rollers and soil testing to avoid potassium deficiencies in annual bluegrass.
Preventive fungicide applications are more effective than curative, according to Rutgers University.
- Other fungicide application tips, according to Rutgers, are:
- Avoid sequential use of any fungicide chemistry
- Tank-mix or alternate fungicides with different modes of action to enhance efficacy and reduce the potential for resistance
- Develop fungicide programs that focus on efficacy and application timing
- Use as many different fungicide chemistries with proven efficacy (QoI, DMI, Nitrile, dicarboximide).