SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/484138
50 SportsTurf | April 2015 www.sportsturfonline.com Q&A with Pamela Sherratt W e have had serious issues with- Poa annua at our rec. sports playing fields. I feel our main contributors are (1) sand-based fields that receive a ton of play in the fall (soccer/flag football); (2) geese eating and disposing their waste full ofPoa seeds; and (3) lack of a solid plan. The first two I can't do much about, but I was hoping you would be able to help with #3. I'm open to any and all suggestions. Poa annua (annual bluegrass) is a winter annual that germinates in the fall, so when athletic fields are heavily used in the fall it is able to germinate in the disturbed soil and quickly gets a foothold. Given that there are anywhere from 150-450 viable Poa annua seeds per sq.ft. in the soil seedbank, it's not surprising that as soon as there is a divot, Poa colonizes it. The biology of Poa is actually quite fascinating. It is a formidable opponent because it is able to adapt to the local climate and thrive where desirable grasses cannot. It is one of the five most widely distributed plants on earth, found on all continents, and it produces copious amounts of seed each year. Most significantly, it is so geneti- cally diverse that many different types of the plant can exist on the field at the same time. Some biotypes are true annuals and some are perennial in nature. On low-maintenance athletic fields the Poa is usually the annual type, but as the cultural intensity of a field is increased the annual type takes on a perennial nature. The perennial type is classified asPoa annua var. reptans. Perennials are characterized by a more stoloniferous growth habit, produce more tillers and shoots, have a deeper root system, and produce fewer seed heads when compared to annuals. The conversion from annual to perennial type is influenced most strongly by mowing stress and research has shown that as long as the mowing stress is present, thePoa will tend to exhibit the peren- nial traits, but once mowing is stopped the Poa would revert to an annual. In essence, it can be whatever it wants to be! There are some field managers, particu- larly in mild climates, that manage Poa rather than spending time and resources trying to eliminate it, but it is largely considered a pest on athletic fields. Since it is a winter annual it typically dies out during summer stress, so it is of no use to field managers preparing fields for summer play. Like a typical annual, it puts all of its energy into seed production so it also has low tillering (density) and shallow roots. Further, it has a light green color, is tolerant of neither heat nor cold, is susceptible to several diseases, and produces an uneven playing surface. The uneven playing surface trait is directly related to its genetic diversity and varying growth characteristics among the Poa plants. Since Poa can adapt to a form that is best suited to the current management conditions, a multi-faceted approach to controlling it is needed. Relying on herbi- cides alone is not the answer, since Poa is conducive to the development of herbicide resistance (according to the Weed Science Society of America there are 27 cases of herbicide resistance in Poa). Cultural man- agement strategies that limit water and fertilizer in the hope of killing it through stress can be somewhat successful but can also have a detrimental effect on the more desirable grasses if taken to the extreme. Some of the tried and tested approaches have included: (1) aggressive overseeding with desirable grasses; this is most successful if quick-germinating species like peren- nial ryegrass are used. (2) hand-picking; (3) avoiding soil disturbance (e.g. coring) during peak germination in the fall; (4) maintaining a healthy mowing height for the preferred grass, since Poa will gain the competitive edge if the mowing height is too low; and (5) doing all that is necessary to grow healthy turf, such as relieving soil compaction and reducing shade. Another option that may open up in the near future involves turf breeding. There has been some advancement in research with athletic grasses like Kentucky bluegrass that show resistance to the active ingredient glyphosate. In practice, glyphosate herbi- cide could be applied to the bluegrass to selectively remove Poa and other susceptible weeds. To date, this grass is not on the mar- ket but the research is encouraging. Make a poa plan Questions? Send them to 202 Kottman Hall, 2001 Coffey Road, Columbus, OH 43210 or sherratt.1@osu.edu Editor's note: This is the debut "Q&A" column for Pamela Sherratt, sports turf specialist at Ohio State, where she teaches sports turf and plant science classes, does applied research, and has some Extension duties. Pamela is originally from England, where she left school at age 16 to pursue an apprentice- ship in horticulture and turf. She was an instructor in sports turf management at Myerscough College before coming to the US for her master's degree at OSU. She has served on the board for STMA and the Ohio chapter of STMA, and was honored with the William H. Daniel Founder's Award in 2003, as well as the OSTMA Founder's Award in 2002 and 2011. Continued on page 49