GOLF COURSE: Update on Poa annua

Members will have noticed our couch fairways, tees and surrounds are infested with more Poa annua than usual this year. Poa annua (or Wintergrass as it is commonly known) is that clump forming grass that typically appears when we get autumn rain and temperatures fall from the summer heat, with this year’s cool damp spring being ideal for it’s survival.

Typically an annual grass, it is highly invasive with each plant able to produce in excess of 2000 seeds, and is extremely adaptable due to its tolerance of low mowing heights (survives in greens) and a variety of soil types and conditions.

Sounds like a good grass? Unfortunately, it has a natural habit to die off in summer due to a lack of heat and drought tolerance, and is very susceptible to fungal diseases and insect pests, and is therefore very unreliable and expensive to manage as a turf species in our climate.

The control of Poa annua has been a focus for turf managers for decades, but in the past 5-10 years it has been increasingly difficult to remove from couch surfaces in particular, not just here, but throughout the southern part of Australia, and indeed overseas.

There are a number of reasons for this, including:

• Expectations of playing surface quality throughout the year means that couch surfaces are irrigated and fertilised for more of the year than was the case 20 – 30 years ago, supporting the growth of Poa annua for longer
• Age of turf surfaces meaning a larger seed bank has accumulated over time
• Older products that were effective no longer being permitted for use on turf for regulatory reasons (generally good reasons)
• New products are very selective in the grass species they target, but there is a very limited number of them available (and importantly the chemistry they contain)
• Some individual plants are genetically more tolerant to these limited chemistries, and the high rate of reproduction of Poa annua means that its own breeding results in individual plants that are able to survive these new product applications and continue to reproduce.
  • Some species of Poa are now classed as perennials

Why do we need to control it in the first place? Apart from looking unsightly and at times compromising playability, if left uncontrolled it con dominate playing surfaces to the detriment of the desirable couch grass and then become a serious and costly management problem, particularly throughout summer.

The extent of the issue was highlighted at a recent forum in Melbourne that was attended by Golf Course Superintendents, independent researchers, and product development company representatives to discuss the extent of the issue and develop a strategy to get better control.

While anecdotally we suspect we may have a chemical resistance issue around the country, scientific studies are needed to determine this, so a number of clubs (including Glenelg) have provided plant material for analysis to determine if this in fact the case, and this work is underway at the moment.

This research is critical as it will allow the industry to establish the extent of the problem and work collectively on a strategy to manage it. In Australia, the turf industry is extremely reliant on very few dedicated local researchers (pathology, entomology) or overseas information due to a lack of funding for such positions, so the challenge will be how to take the next step.

In the meantime, members can be assured we are doing all that we can to manage the issue, and remain committed to provide the best possible playing surfaces in a sustainable manner.

Daryl Sellar
Course Superintendent