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Are Etiolated Tillers A Visual Nuisance or Something Else?
October 1, 2008 By: Mike Fidanza, Jeff Gregos, Dan Brickley TurfGrass TrendsUpon close inspection, several organisms have been isolated from affected turfgrass: Fusarium sp., Rhizoctonia sp., bacteria (unknown sp.), Ascocyta sp., Leptosphaerulina sp., Dreschslera sp., and Pythium sp. The role these organisms play on ETS is not clear. Recently reported in New Zealand, the appearance of etiolated leaf blades in turfgrass was called "mad tiller disease" (Stewart). Fungi isolated from affected tillers of ryegrass in New Zealand included Fusarium culmorum, Fusarium crookwellense and Rhizoctonia solani (Stewart). Although these fungi cause foliar, crown and root diseases in plants, many Fusarium fungi also produce plant growth hormones called gibberellins (Agrios, Ioos). Japanese farmers will occasionally find an elongated rice plant, which they call bakanae or "foolish seedling" disease, where the extended tiller becomes yellowish and necrotic and then dies. In rice, this disease is caused by the fungus Fusarium moniliforme, which also is known to produce gibberellins (Desjardins, Sun). At this time, it is unknown if ETS is related to "foolish seedling" disease of turf.
What exactly is the cause of ETS in turfgrass? Several hypotheses are being investigated. The appearance of etiolated leaf blades is most likely due to excessive amounts of gibberellins perhaps accumulating in meristematic plant tissue. This over-production of gibberellins could be the plant's defensive reaction to colonization of xylem tissue by bacterial or fungal species that might or might not be pathogenic to the turfgrass plant. Some bacterial and fungal organisms that potentially are primary or secondary invaders of turfgrass are known to produce gibberellins themselves, which can indirectly contribute to the elongation of the newest leaf blade (Taiz). The relationship of turfgrass maintenance practices and ETS is also being investigated. Should this condition be labeled a plant disease, or is this some plant physiological disorder?
Research is needed to answer these questions.
What can be done to control ETS or mad tiller symptoms in turf? Even though the exact cause of ETS is not decisively known at this time, fungicides and plant growth regulators commonly applied to fairway turf in summer maintenance programs have been evaluated in field studies in 2004, 2005 and 2006. The objective was to evaluate any potential association with ETS and plant protection products, including fungicides and PGRs.
Note: Fungicides and PGRs are not labeled for the management or control of etiolated tillers in turfgrass. The field studies were conducted on a perennial ryegrass fairway with a history of ETS at Lebanon County Club. In 2004 and 2006, the actual number of etiolated tillers were counted per plot. In 2005, an estimate of the percent plot area affected with etiolated tillers was visually determined due to the severe amount of etiolation.
 Microscopic view of elongated cells from an etiolated perennial ryegrass leaf blade. (Photo by Jeff Gregos) |
Overall, a noticeable reduction in the visual appearance of ETS was observed in plots treated with fungicides that contain an active ingredient of a demethylation inhibitor. A reduction in ETS was also observed in plots treated with the PGR products, which were only included in that 2005 field study. Most all other fungicides tested had no effect or influence on the incidence of ETS in those perennial ryegrass field studies.
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Although a few plant protection products show promise for helping to manage ETS, the cost of using those products could be a challenge to golf course superintendents. Therefore, more field testing and plant physiology-based greenhouse and laboratory research is warranted to fully understand ETS in turfgrass. For now, the cautious use of PGRs with frequent mowing helps to minimize the visual appearance of ETS, especially those elongated leaf blades.
Mike Fidanza, Ph.D., is a turfgrass specialist at Penn State University. He can be reached at maf100@psu.edu .
Jeff Gregos is principal in GEC Turfgrass Consulting in Moon Township, Pa. He can be reached at jeff@gecturf.com .
Dan Brickley is superintendent at the Lebanon Country Club and can be reached at djb301@yahoo.com.
REFERENCES
1. Agrios, G.N. 1978. Plant Pathology. 2nd ed. Academic Press, Orlando, FL.
2. Desjardins, A.E., H.K. Manandhar, R.D. Platter, G.G. Manandhar, S.M. Poling, and C.M. Maragos. 2000. Fusarium species from Nepalese rice and production of mycotoxins and gibberellic acid by selected species. Applied and Environmental Microbiology 66:1020-1025.
3. Ioos, R., A. belhadj, M. Menez, and A. Faure. 2005. The effects of fungicides on Fusarium spp. and Microdochium nivale and their associated trichothecene mycotoxins in French naturally-infested cereal grains. Crop Protection 24:894-902.
4. McMahon, M.J., A.M. Kofranek, and V.E. Rubatzky. 2002. Hartmann's Plant Science: Growth, Development, and Utilization of Cultivated Plants. 3rd ed. Prentice Hall, Upper Saddle River, NJ.
5. Salisbury, F.B. and C.W. Ross. 1985. Plant Physiology. 3rd ed. Wadsworth Publishing Company, Belmont, CA.
6. Stewart, A. 2002. Mad tiller disease: a common but only recently named condition in turf. New Zealand Turf Management Journal. 17(8):25-26.
7. Sun, S.K. and W.C. Snyder. 1981. The bakanae disease of the rice plant. p. 104-113. In: P.E. Nelson, T.A. Toussoun, and R.J. Cook (ed.) Fusarium: diseases, biology, and taxonomy. The Pennsylvania State University Press, University Park, PA.
8. Taiz, L. and E. Zeiger. 1991. Plant Physiology. Benjamin/Cummings Publishing Company, Redwood City, CA.
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