Tough growing on golf courses in 2010
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
2010 began as a stressful year for many golf courses that suffered winterkill injury; the summer has not been any easier for managing turf in Michigan. Precipitation patterns since June have been sporadic with many areas receiving excessive amounts of rainfall while others may actually be in a deficit. Grand Rapids recorded 8 inches of rainfall in June, 4 inches higher than average. In June, higher than average rainfall was also reported in Detroit, Traverse City, and Gaylord. Much of this rainfall was from single events and despite the high monthly totals, there have been turfgrass areas that are actually being stressed from lack of moisture. Rainfall in July has been closer to average, but the combination of rainfall, high air temperatures, and high relative humidity have been a perfect combination for enhanced disease activity and turfgrass decline.
Irrigation systems tested
Looking back, 2009 was an extraordinary year when many golf course superintendents discussed how long they had gone before or between using their irrigation systems. Frequent rainfall and cool temperatures resulted in optimal turfgrass growing conditions. In contrast, 2010 has been less consistent and inefficiencies in irrigation systems have been revealed on many courses. Turfgrass areas that reveal poor irrigation coverage first are typically edges of fairways, banks of greens, tees and bunkers and the rough. Many of these areas are also high traffic areas that are subject to compaction. Some of these trafficked, compacted, heat-stressed areas may need to be reestablished this fall. In an effort to compensate for poor irrigation coverage and improve water management, hand-watering has become commonplace on golf course putting greens. In a time when most budgets have been shrinking, superintendents may be challenged to add hand watering to an already stressed labor budget.
Salty irrigation water
Another problem that occurs on some golf courses during dry summers is the effect of high salt content in irrigation water. The high salt content makes it difficult to prevent turf wilting. Roots take up water by a process called osmosis. Osmosis works on the principle of there being a higher salt content in the root than the soil causing the water to flow into the plant. The higher the salt content in the soil, the more difficult it becomes for the plant to take up water. If the salt concentrations become high enough in the soil solution, the water will not flow into the root. If salt content becomes really high, the water in the root will actually begin to flow out into the soil. In any event, it makes it difficult for the turfgrass plant to survive. If you’re been fortunate enough to receive adequate rainfall, the rain will flush the salt out of the root zone so the salty irrigation water has minimal effect on the turf. If your course has not been receiving rainfall to flush the salts, when turf is irrigated with high salt content irrigation water, it is important to flush the greens at least once a week to try to dilute the salt level in the soil. Golf courses should also consider switching to city water; either entirely or at least to dilute the salt content of the irrigation water. If you’re unsure about your irrigation water quality, conduct an irrigation water test so you know where you stand.
Disease and insect problems
High air temperatures combined with high relativity humidity and isolated heavy rainfall has resulted in some of the highest disease pressure we have seen on golf courses in several years. In June what started with nuisance fairy ring on fairways and greens has progressed to include anthracnose, summer patch, brown patch, Waitea patch and the sporadic case of Pythium blight. This year, because of the high temperatures, bacterial wilt has become a problem on many greens. There are two different bacterial pathogens involved – one that is attacking annual bluegrass and one that is attacking the creeping bentgrass. Unfortunately, there is no available chemical control for either of these diseases, the best that can be done is to raise the mowing height and not allow the turf to go under drought stress. As the summer progresses, other pests may become problematic. Black turfgrass Ataenius may begin to cause damage in late July and early August. These small white grubs can damage fairways, tees and greens. Japanese beetle and European chafer grubs may also cause damage later this summer. Japanese beetle grubs are likely to be a problem in irrigated turf, like golf course fairways. European chafer is a problem in unirrigated turf such as golf course rough.
Golf course microclimates with shade, poor air circulation and poor drainage are the toughest to manage disease pressure. Typically, the worst turf damage occurs on greens surrounded by trees and underbrush. Trees and underbrush restrict air movement in green complexes and result in higher temperatures and the inability of the plants to cool themselves through transpiration. The lack of air movement in these areas often leads to greater incidence of turfgrass diseases, which can also lead to turfgrass loss. Another factor that contributes to turfgrass thinning on greens, especially during warm summers such as this year, is a lack of morning sun during July and August. A lack of morning sun on creeping bentgrass greens may be particularly devastating. The reason the turf may thin due to a lack of morning sun is because the turfgrass plant only photosynthesizes when temperatures are below 85°F. Especially this summer, temperatures have normally been below 85°F in the morning, not in the afternoon. If the plants cannot photosynthesize, they run out of energy, and will eventually die. Now is the time to document greens that may be suffering due to lack of morning sun, poor air circulation and enhanced disease activity. Consider removing or thinning trees and underbrush on the east and northeast side of greens to facilitate morning light and air movement.