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 Photo by: Cale Bigelow in West Lafayette |
Over the past week a relatively new turf malady has become prevalent on golf turf throughout the region. This new phenomenon has been referred to as “Mad Tiller Disease”, and “Ghost Grass” in the United Kingdom , but using more technically appropriate terminology “Etiolated Tiller Syndrome (ETS)” is what many turfgrass scientists are calling it. Check out the photo from one of our research plots at Purdue and turf agronomist Steve McDonald of Turfgrass Disease Solutions located in the Philadelphia area to see what ETS looks like.
If you are not familiar with the term “etiolation”, the American Heritage Dictionary defines the term as: “A pathological condition of plants that grow in places that provide insufficient light… It is characterized by elongated stems and pale color due to lack of chlorophyll.” Etiolation is a common physiological response of turf grown in shaded conditions. ETS seems to occur most frequently following periods (a day or so) of cloud cover, and rain. In fairways creeping bentgrass is normally unaffected but the annual bluegrass ( Poa annua ) leaves elongate very rapidly, extending 1-2 inches above the canopy. Upon closer inspection of the leaves large portions of the leaf tissue appears bleached white. Although it has been primarily confined to annual bluegrass, Dr. Karl Danneberger has noticed it on creeping bentgrass, perennial ryegrass and Kentucky bluegrass since the fall of 2005 in Ohio . The white leaf appearance is most likely due to the rapid leaf elongation which dilutes the chlorophyll in the leaf blades.
Theories abound on why this abnormal growth occurs. Suggestions include possible micronutrient deficiencies, bacterial wilt, infection by a Fusarium spp., that produces a gibberellic acid (GA)-like compound, and certain plant growth regulator programs. GA is a naturally occurring plant hormone responsible for cell elongation. At this point everything is speculation and there is no definitive reason for the ETS phenomenon.
What we do know is that plants respond to inadequate light, or shaded conditions by extending their leaves, hence why it seems to occur following cloudy periods. Overcast conditions and enhanced moisture conceivably could favor leaf infection by a fungal organism, if this fungus produces a GA-like compound, which causes the cells to expand then an abundance of GA would result in very rapid elongation. What is interesting is that many golf course managers regularly apply plant growth regulators that inhibit GA production. On a personal observation in my research plots where these products have been applied I have not noticed a great deal of difference and ETS still occurs in plots receiving GA inhibitors.
So far, ETS has been reported from West Lafayette to Connecticut and down through the Philadelphia area, basically the entire cool-humid region where bentgrass/annual bluegrass fairways are most common. At this point ETS appears very cosmetic, and more of a nuisance which disrupts the overall uniformity of the turf stand, much like another disease, yellow tuft. The symptoms are most obvious on fairways that have not been mowed and they seem to dissipate rather quickly without turf loss. As the weather changes I would suspect that ETS will fade and the undesirable plant response should fade rather quickly. I have not correlated the phenomena with any specific management practices, nor has anyone reported anything that will control it. As things progress with our understanding of this new malady we will certainly keep you posted.