After dealing with some significant thinning of several greens the past two summers caused by etiolation, we got through 2012 with minimal turf damage. How? Well, it certainly was not because of a lack of weather-related stress on the turf, as July tied or broke several heat records.
Basically, the symptoms of etiolation in turf are thin, pale and elongated plants, similar to what you’d see in white asparagus. Eventually, the weakened turf can collapse and die. On putting greens, samples exhibiting these symptoms also tend to have high bacteria counts, which can clog the plant’s "blood stream." This is where the debate among members of the scientific community occurs: Is the bacteria a cause of the etiolation and subsequent wilt, or merely a secondary pathogen, that is taking advantage of an already weakened plant?
Whether the bacteria is a cause or effect, is not important from our perspective. Regardless of the actual cause, preventing, controlling, and managing etiolation has become the goal. With that in mind, over the past two years we’ve worked at developing a set of best management practices in dealing with etiolation in the greens by researching countless articles, attending seminars, discussing the issue with other course managers, consultants and scientists from around the country, and even offered the use of our practice green for a USGA funded study.
One plant pathologist believes there is a connection between the occurrence of etiolation and turf fertility. While we have always kept the greens fairly lean, his recommendation was to cut back on the amount of Nitrogen applied even further. This seems to have been a key.
However, this method is not without some risk. Because a putting green is built largely out of sand, which has little nutrient holding capacity, as we entered the summer, it was like sending a marathon runner off to race without having a good carbohydrate supply to use for energy--essentially, the turf got the equivalent of an occasional sports drink to make it through the summer. To put this into perspective, your home lawn would typically receive 1 lb. of Nitrogen /1,000 square feet per application of fertilizer. While applying that much Nitrogen to a putting green in-season would never be a wise idea, we are now applying a miniscule rate of 0.03 lb./1,000 square feet.
In addition to this lean fertility program, we also stayed very aggressive with our mowing and rolling regimen throughout the summer. Raising the height of cut is a well documented way of decreasing plant stress, but we chose not to do that. And, from June 6 through August 13, the greens were mowed a minimum of once (and often twice) per day, every day. The idea behind these decisions was that etiolation is much like a plant growing out of control. If we didn’t mow every day, there was a high likelihood that we would "scalp" the turf when we resumed mowing.
When you step back and look at some of the practices, they are counterintuitive to maintaining a healthy green, and so go against some of the rules of thumb of how to decrease plant stress. For example, mowing is a stress on the turf. And yet, in this case, if we chose not to mow, an even greater physical injury to the plant would occur. So how do you stop etiolation? In our case, the answer seems to be, by not managing the turf in a conventional manner.
|In this picture from 2011, patches of etiolated Bentgrass can be seen in the collar.|