Golf Course Management

AUG 2018

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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66 GOLF COURSE MANAGEMENT 08.18 The RESEARCH SAYS • Herbicide resistance is quickly becoming the No. 1 agronomic problem the golf industry faces. • Poa annua management regarding herbicide resistance involves alternating and/or combining products with different modes of action. • One means of reducing herbicide loads — another component of resistance management — is to delay herbicide application into mid-fall and to combine products. courses have become so desperate for P. annua control that they are willing to apply very low rates (~¼ normal use rate) of either EPSPS, glutamine synthase or PSI inhibitors. Obvi - ously, establishing a test plot on your course under usual environmental conditions will in - dicate whether the results are acceptable. Golf greens Because of their sensitive nature, non- overseeded golf greens are in double jeopardy when it comes to acceptable P. annua control and turf safety. In addition, some products cannot legally be applied to greens, and some products just aren't very effective. Overall, the control strategy for greens is similar to that for fairways and roughs, but fewer herbicide choices are available. Basically, only two pre- emergence herbicides (dithiopyr and a combi - nation of oxadiazon and bensulide) and only two post-emergence herbicides (foramsulfu - ron and pronamide) are available on greens. erefore, turf managers should alternate be - tween the two pre-emergence products and choose one of the two post-emergence prod - ucts. e next year, these would be alternated. For example, in year 1, dithiopyr would be paired with foramsulfuron. In year 2, oxadia - zon + bensulide would be paired with pron- amide. In year 3, dithiopyr would be paired with pronamide, while in year 4, oxadiazon + bensulide would be paired with foramsulfu - ron. is avoids using a pair of products with similar modes of action in two consecutive years. Jugulam, B. Friebe and B.S. Gill. 2018. Extrachro- mosomal circular DNA-based amplification and transmission of herbicide resistance in crop weed Amaranthus palmeri. Proceedings of the National Academy of Sciences 115(13):3332-3337. 11. Lowe, D.B., G.A. Swire-Clark, L.B. McCarty, T. Whitwell and W.V. Baird. 2001. Biology and molecu - lar analysis of dinitroaniline-resistant Poa annua L. International Turfgrass Society Research Journal 9:1019-1025. 12. Lush, W.M. 1989. Adaptation and differentiation of golf course populations of annual bluegrass (Poa annua ). Weed Science 37:54-59. 13. Mao, Q., and D. R. Huff. 2012. The evolutionary origin of Poa annua L. Crop Science 52:1910-1922. 14. McElroy, J.S., M.L. Flessner, Z. Wang, F. Dane, R.H. Walker and G.R. Wehtje. 2013. A Trp574 to Leu amino acid substitution in the ALS gene of annual bluegrass (Poa annua ) is associated with resistance to ALS-inhibiting herbicides. Weed Science 61:21- 25. 15. Toler, J.E., T.G. Willis, A.G. Estes and L.B. McCarty. 2007. Postemergent annual bluegrass control in dor - mant nonoverseeded bermudagrass turf. HortScience 42:670-672. Bert McCarty (bmccrty@clemson.edu) is a professor of turfgrass science and management at Clemson University in Clemson, S.C., and Fred Yelverton is an Extension spe - cialist in turfgrass and forage and crop weed management at North Carolina State University in Raleigh, N.C. Conclusions We believe herbicide resistance is the No. 1 potential agronomic problem facing the turf - grass industry. Without proper stewardship of existing products as suggested in this article, it is not a question of if resistance is going to occur, just when. Using products with differ - ent modes of action is the best means we cur- rently have to help combat this issue. Once resistance to a particular mode of action oc - curs, that product's effectiveness is lost for the foreseeable future. Acknowledgments is article is an outreach from meeting with various company technical and research representatives who agree with the authors on the seriousness of herbicide resistance in the turfgrass industry. References and additional reading 1. Binkholder, K.M., B.S. Fresenburg, T.C. Teuton, X. Xiong and R.J. Smeda. 2011. Selection of glypho - sate-resistant annual bluegrass (Poa annua ) on a golf course. Weed Science 59(3):286-289. 2. Christians, N. 1996. A historical perspective of annual bluegrass control. Golf Course Management 64(11):49-57. 3. Cross, R.B., W.C. Bridges Jr., L.B. McCarty and J.S. McElroy. 2015. Evaluating annual bluegrass herbicide resistance evolution in golf course fairways. Weed Technology 29:488-500. 4. Cross, R.B., L.B. McCarty, N. Tharayil, J.S. McElroy, S. Chen, P.E. McCullough, B.A. Powell and W.C. Bridges Jr. 2015. A Pro106 to Ala substitution is associated with resistance to glyphosate in annual bluegrass (Poa annua ). Weed Science 63:613-622. 5. Cross, R.B., L.B. McCarty, J.S. McElroy, N. Tharayil and W.C. Bridges Jr. 2015. Comparison of enzyme and growth characteristics in ALS-inhibitor suscep - tible and resistant annual bluegrass (Poa annua ) biotypes. Weed Science 63:220-228. 6. Gressel, J., and L.A. Segel. 1990. Modelling the effectiveness of herbicide resistance and mixtures as strategies to delay or preclude resistance. Weed Technology 4:186-98. 7. Heap, I. 2016. International survey of herbicide resis - tant weeds. (www.weedscience.org) Accessed June 25, 2018. 8. Isgrigg, J., III, F.H. Yelverton, C. Brownie and L.S. Warren Jr. 2002. Dinitroaniline resistant annual blue - grass in North Carolina. Weed Science 50:86-90. 9. Kelly, S.T., G.E. Coats and D.S. Luthe. 1999. Mode of resistance of triazine-resistant annual bluegrass (Poa annua ). Weed Technology 13:747-752. 10. Koo, D., W.T. Molin, C.A. Saski, J. Jiang, K. Putta, M.

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