Thursday, April 2, 2015

Promoting Bentgrass over Annual Bluegrass (Poa annua)

Promoting Bentgrass

In my previous post I mentioned promoting Creeping Bentgrass over Poa annua and why it is important to Metamora. With golfer expectations of faster green speeds, Poa annua putting surfaces are becoming more and more expensive to maintain. Poa annua requires more inputs than bentgrass. It requires more labor, more water, more fertilizer and more pesticides.

To promote bentgrass, we must manage for bentgrass. We keep the bentgrass healthy while keeping the Poa annua under as much stress as possible. When Poa annua is under stress it is prone to more diseases. When those diseases infect it, we keep a very close eye on it and will treat for those diseases when absolutely necessary.

How do we manage for bentgrass?

We do not use a lot of granular fertilizers which benefits Poa annua, and use more foliar applied fertilizers. We also try and keep all the surfaces firm, this is achieved by drying them out as much as possible by watering deep and infrequently. Poa annua has a shallow root system and we try and deprive it of water at the surface and in the upper root zone when possible. Another important practice that we do is not disrupt the surfaces in the spring and early fall. Poa annua is very opportunistic and is most aggressive in spring and fall. We also use a plant growth regulator that is not as friendly to Poa annua. Plant growth regulators do exactly what they say, they regulate plant growth. This allows us to mow less and roll more a practice that benefits bentgrass. We also topdress very lightly once a week, this also puts less stress on bentgrass. You can read more about that under the cultural practice label.

Winter weather

When harsh winters are predicted some courses go to great lengths to keep their Poa annua greens healthy. Covering greens is practiced to protect Poa annua from subzero temperatures and desiccation. Some courses are even removing snow off their greens all winter long to keep ice from forming. This requires more off season labor and more equipment. All of these practices are understandable when maintaining Poa annua putting surfaces. Bentgrass however is much more tolerant to winter weather. In fact, no extra care needs to be taken to prevent winter damage to bentgrass at least in Michigan. Bentgrass can tolerate temperatures well below zero. Bentgrass can survive under ice cover from 90 days and possibly all the way up to 120 days. Poa annua can become compromised at 30 days under ice and plant death often occurs between 45 and 60 days under ice. Last winter golf courses in South Eastern Michigan experienced this and some even this winter. Fortunately, this winter wasn't nearly as bad as last winter, but still bad enough to damage or kill Poa annua.

Like I stated in previous posts, Metamora has a lot of bentgrass in the playing surfaces and that is why it is promoted. Last winter, some of the Poa annua got damaged, but we were able to get more bentgrass into those areas. Below is a picture of #17 green last spring, this spring and a close-up of an area that was killed last year to demonstrate how much more bentgrass is in that green now.

Spring of 2014
This spring
The lighter green is Poa annua

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