With the winter months well and truly upon us, we find that wintergrass or Poa annua becomes more obvious in our putting surfaces.
This weed is probably the major issue faced by turf managers around the world, in putting surfaces, and continues to be so. It's presence can cause less than ideal ball role as its growth rate is much quicker than the desired species of bentgrass and this occurs throughout the daylight hours.
Though it is an annual grass, the conditions that it experiences in greens are so favourable that it will survive all year round and as such is always evident but more obvious through the colder wetter months.
There are limited effective controls for wintergrass in bentgrass turf and as such it is difficult to totally eliminate from putting surfaces once it gets a hold.
We currently have a programme with two separate products to help reduce its prevalence and restrict its development further.
The first is the use of a growth retardant that reduces it vertical growth and shrinks the plant to allow the desired species of bentgrass to overtake it or 'crowd it out'. The second product is a contraceptive to inhibit the wintergrass from flowering and in turn seeding which should lead to a reduction in plant numbers.
Another issue facing use with wintergrass management is the number of genotypes of wintergrass that occur. Some sites in Australia have recorded up to a dozen genotypes being evident and chemical controls may work on some and not others and over time the uncontrolled genotypes may dominate the turf sward leaving a site with a prominent infestation of uncontrollable wintergrass.
Both these programmes tend to yellow wintergrass making it more visible by eye at this time of year hence it becomes more obvious.
Unfortunately there is no 'silver bullet' for wintergrass control in bentgrass at this time but chemical manufacturers and turfgrass research organisations are constantly trying to develop improved control products.
We have this winter trialled the use of a growth retardant and fertiliser combination product on the 10th green to evaluate its benefit in our overall programme and it does seem to have some positive elements to its use at this time.
At this time however a broad management programme that involves controlled nutrient application and the use of the other products described is the best solution.
Yellow stunted wintergrass under chemical control on the 10th green site. The greener darker desirable bentgrass can be seen surrounding the wintergrass and competing with the wintergrass plants.
This photo shows the area on 10th green where wintergrass has been controlled and succumbed to chemical pressure. The healthy desirable bentgrass can be seen around the bare area and this will now creep and develop into the bare area as weather improves.
