ANNUAL Bluegrass…A Fitting Name, Unfortunately
By Adam Moeller, AgronomistJuly 30, 2010
Annual bluegrass turf, particularly on putting greens, is hanging on for dear life at golf courses across the Northeast Region, and at many courses it has given up. Anthracnose, summerpatch,annual bluegrass weevils, parasitic nematodes, heat and/or drought stress, wet wilt, scald, etc. are all responsible, and no doubt 2010 will be burned in the memories of many turf managers for a long time to come. June and July could be the hottest on record in some locations, and when high temperatures are combined with humid conditions and sporadic thunderstorms, turf decline can be difficult or impossible to control. Annual bluegrass turf, which has very poor stress tolerance compared to creeping bentgrass, is caving in first, but even bentgrass is failing in some situations. It feels as though the equator shifted north by a couple hundred miles this year, and our grasses are simply not equipped to deal with the added stress the weather is producing.
Just about all turfgrass diseases are exacerbated in stressful weather, and many are causing damage this year. Anthracnose and summer patch are destructive diseases of annual bluegrass putting greens and have been seen on all over the region. However, root Pythium, nematodes, and bacterial infections are causing damage, too. Even courses with sound cultural programs and excellent fungicide selection, timing, rates, and application intervals are experiencing disease breakthrough. Why? Fungicides do not kill pathogens -- they suppress them. The term fungistatic more accurately describes most materials, and the effectiveness of most fungicides can be reduced if disease pressure is high enough.
General decline from heat stress has occurred on many golf course putting greens as well. Imagine trying to run a marathon when it’s 95o F and humid without having access to water. This is essentially what has happened to many annual bluegrass putting greens. Turf plants are losing energy rapidly and are under so much stress that they can’t cool themselves fast enough. Unfortunately, a lot of grass isn’t going to finish the race. Low mowing heights, low soil oxygen caused by poorly draining greens, concentrated traffic, and poor microclimates with shade and air flow problems are the most common issues that have pushed turf into severe decline. However, even the best programs have had problems this year.
Most courses have lost grass; some are just worse off than others. Microclimates, grasses, rootzone drainage, labor and maintenance resources, and expectations are unique at every golf course, and these factors explain the level of injury. At some point the weather is going to break, but it might be awhile. Attempting to alleviate plant stress is something all turf managers in the region have already done. Reduce putting green stress by raising the height of cut, reducing mowing frequency, rolling instead of mowing, switching to solid front rollers on greens mowers, avoiding mowing wet greens, regular applications of soluble nitrogen and fungicides, periodic venting to improve rootzone gas exchange, and irrigating and syringing the turf as accurately as possible. Even with all these practices, in some instances, decline has still occurred. Closing a green also may be necessary to allow for recovery. At this point, golfers need to realize that most putting greens are just barely hanging on, and turf loss is extremely difficult to prevent in a summer like 2010.
