If I’m Sneezing, It Must Be Spring!
By David A. Oatis, director, Northeast Region
May 12, 2011
|Off color bentgrass at this time of year is usually due to cool temperatures and mechanical injury.|
|Adjacent annual bluegrass may be unaffected. Newly established AB usually seeds prolifically and will likely be more susceptible to stress and disease later in the season.|
It is always interesting to watch the growth and development of putting green turf in the spring. Initially, bentgrass outgrows annual bluegrass (AB) and turf managers everywhere are hopeful that bentgrass populations have increased. Typically, a few weeks later, hopes are dashed as the growth rate of annual bluegrass suddenly outpaces the bentgrass, giving rise to the concern that the “annual bluegrass is taking over!” This is where many courses are now. When temperatures rise a bit more and stay consistently warmer, this appearance will dissipate and the next phase will kick in: the “June swoon” of annual bluegrass. Once AB’s energy is expended in producing a seed head, the plants turn yellow and their growth rate slows dramatically. For turf managers with lots of AB, this also can cause concern. So what is the point of all this? Most golfers look at putting greens and think of them in a “singular” sense. However, each green is comprised of millions of individual plants, most falling into 2-3 species: annual bluegrass, creeping bentgrass, and perhaps velvet bentgrass. Note also that there are thousands of different biotypes of each species present, and the growth rates of these grasses vary. So if you are wondering why the greens are not smooth as glass, these are the reasons.
• Bentgrass throughout the middle and southern part of the Northeast Region now is showing the effects of cool nights and mechanical injury. Plenty of bentgrass is off color, has a bronze cast, and may be experiencing some thinning. AB right next to the bentgrass looks perfectly healthy. Many misdiagnose this as leaf spot, and while a disease may be involved, it usually is nothing more than the weather. When warmer temperatures arrive, the growth rate of the bentgrass will take off, and the discoloration will dissipate.
• There are plenty of AB seedheads throughout the region this year, especially at courses that did not treat preventively for seedhead formation due to injury suffered last summer or this last winter. Seedhead production is particularly heavy in areas that sustained damage. Keep in mind that the prolific seedhead production in the damaged areas is a sign that newer, weaker AB has become established. These weaker biotypes will be more susceptible to stress and disease later this summer. If your course has a lot of AB seeding in the damaged areas, more conservative management may be in order this year. In time, the weaker annual bluegrass biotypes will be replaced with better ones, and later with more bentgrass. However, for the first year or two after damage, they will be a bit more susceptible to turf loss.