Disease and Pest Management
Anthracnose, dollar spot, Pythium foliar blight, brown patch, summer patch, microdochium patch and gray snow mold can have a significant deleterious impact on Poa annua putting greens. Depending on the location, these diseases may not all be a concern, but if Poa annua is being maintained, a preventative disease management program must be put in place to control diseases that are likely to occur because an outbreak can be devastating.
A successful disease management strategy for Poa annua greens will need to incorporate appropriately timed cultural practices and preventative fungicide applications. Online resources, like NC State’s TurfFiles and the publication Chemical Control of Turfgrass Diseases 2020, can make it much easier to choose the appropriate active ingredients, to properly time applications, and minimize the risk of developing fungal resistance.
For those managing Poa annua putting greens in locations where microdochium patch pressure is high, research conducted at Oregon State University can be used to develop an effective control program using fungicides (Macdonald, 2014). Additionally, research has been performed to evaluate alternative methods for reducing the number of plant protectant applications to control this disease (Mattox, 2020).
Evaluate which plant protectants you plan to apply to determine if a certain class can be used to control multiple diseases. For example, a properly timed application of a Qol product when disease pressure is high for both anthracnose basal rot and brown patch can result in control of both diseases. Incorporating this type of thought process before each application makes for more efficient management and better environmental stewardship.
Similar to disease control, a preventative strategy is often employed to control insect pests. Putting greens should typically be included with grub control programs in the spring. In locations where annual bluegrass weevil (ABW) can be found, additional control strategies have to be put in place. Damage from the ABW is not often an issue on putting greens but collars can be hard hit.
Control programs targeting ABW should focus on both the adults and larvae. Multiple applications can be necessary when pressure is high from these pests. Scouting must begin in the spring and continue throughout the season since multiple generations will occur.
A nutrient analysis should be conducted every year on each putting green to guide fertilizer applications. There is no one-size-fits-all program that can be applied to every golf course with Poa annua putting greens. Location, soil types, expectations and overall conditions must be given consideration when tailoring a fertility program to fit the needs of a golf course. The USGA article “Turfgrass Fertilization” illustrates how a successful nutrient management program can be developed.
When compared to creeping bentgrass, the amount of nitrogen applied throughout an entire season will likely be higher with Poa annua putting greens. Aiming for between 3 and 4 pounds of nitrogen per 1,000 square feet is a good starting point and then adjustments can be made from there. In locations where the turf is growing for most of the year, it would not be out of the question to be above this range.
A sound fertilizer program will also have a positive impact on reducing disease occurrence. For example, anthracnose is more severe when ultra-low rates of nitrogen are applied. This is just one way the benefits of a sound fertility program extend beyond providing nutrients for the turf.
Growth Regulation and Seedhead Suppression
The concept of using both fertilizers and plant growth regulators (PGRs) may seem counterintuitive, but each has their place in a successful agronomic program. PGRs will improve smoothness and consistency on Poa annua greens – especially later in the day – and they help the turf conserve carbohydrates and suppress seedheads when applications are properly timed.
Superintendents used to suppress seedheads by applying the PGRs mefluidide or ethephon tank-mixed with trinexapac-ethyl in spring. Mefluidide is a PGR many superintendents relied upon, but this product is no longer being produced. Recent research conducted by Dr. Sean Askew at Virginia Tech University confirms ethephon applications can be better timed to achieve improved seedhead control compared to a spring-only program. By making an application of ethephon in the late fall or early winter and then following up with tank-mix applications of ethephon and trinexapac-ethyl in spring, better seedhead suppression will result when compared to spring-only applications (Askew, 2016).
Spring applications for seedhead suppression should be timed by using growing degree days and monitoring local conditions. Good indicators to keep an eye on are seedhead emergence in the rough and on south-facing slopes, bunker faces and cart path edges. Soil temperatures typically increase faster in these areas causing seedheads to emerge earlier.
Should seedheads emerge on greens, cultural control through grooming or brushing is a sound approach to remove seedheads and improve smoothness. It is likely that the putting greens will need to be groomed or brushed multiple times to remove seedheads.
Typically, the focus of seedhead control is in the spring but golf courses in certain areas of the Pacific Northwest can experience seedhead emergence in the fall. Removing seedheads through grooming and brushing has been the go-to method for controlling seedhead emergence at this time of year. USGA-funded research is being performed at Oregon State University to determine if ethephon can be safely and effectively used at this time of year for seedhead control.
Once seedheads are controlled in the spring, the focus of PGR applications should shift to managing growth to optimize turf health and playability. Trinexapac-ethyl and prohexadine-Ca are the go-to options when it comes to managing the growth of Poa annua putting greens.
Research conducted by Dr. Bill Kreuser at the University of Nebraska has proven that using growing degree days to schedule PGR applications is the most effective strategy for keeping the turf consistently regulated (Kreuser, 2015). Remember that applying a higher rate of PGR, especially above what the label states, will not extend the duration of regulation.
Water Management and Heat Stress
For those maintaining Poa annua playing surfaces, success hinges on being able to properly manage water. The shallow root system of Poa annua places even more of an emphasis on water management because the turf is not taking up water from deep within the soil profile. The transition from dry to damaged, or dead, can be quick.
Moisture levels should be monitored daily with a moisture meter and any deficits corrected through hand watering or adjusting run times for each green so overwatering is avoided. Simply setting the same run time for all the greens will likely lead to overwatering and the development of turf health issues.