The Fourth of July is a major milestone for turf managers every year. The second wave of adult annual bluegrass weevils usually emerges right around July 4, and they were true to form this year. Adult weevils have been observed on many golf courses for the past few weeks so, depending on where your course is located, the next round of annual bluegrass weevil damage will likely begin in the next two to four weeks. Most areas of the region have only experienced hot weather in short bursts, so stress levels on turf have been high but not excessive. Disease pressure has been high in some areas, but for many areas it has only been moderate… so far. However, this is likely to change as the Fourth of July also signals the start of the most stressful 50-day period of the season. Summer patch and anthracnose are beginning to appear in different areas, and this is a sure sign that stress levels are increasing.
Many courses are still in the process of opening their greens for play following last winter’s catastrophic injury. One positive for courses that sustained winter injury is that many now have considerably more bentgrass in their greens than they did in the past. However, cutting heights are still elevated at many courses that suffered significant winter injury; therefore, playability will not reach the levels attained in recent, past seasons. Keeping cutting heights elevated for the season will help immature, new bentgrass survive. For courses that have significantly higher bentgrass populations, management programs should now be adjusted to promote and sustain healthy bentgrass through the summer.
If your course falls into this category, consider the following:
- Tree work will be needed around many of the greens that now have higher bentgrass populations. The environment that sustained a bent/poa turf may not have enough light for bentgrass to be competitive. Bentgrass has a high light requirement and light penetration must be maximized at all times of year for it to have a fighting chance against annual bluegrass.
- Rethink your cultivation program. Remember that annual bluegrass is a winter annual and aerating or performing surface cultivation during the window of germination will promote annual bluegrass at the expense of newly established bentgrass.
- Creeping bentgrass got its name for a reason, it “creeps.” Using solid rollers, even at lower cutting heights, helps promote lateral growth. Periodic verticutting in the spring and early summer months also can promote more gains in bentgrass, but avoid frequent, aggressive treatments that cause constant wear injury. Constant wear injury tends to favor annual bluegrass.
- Keep wear injury in mind, particularly in lower light environments. Annual bluegrass is more wear-tolerant than bentgrass, and a high-wear program (e.g., frequent double cutting combined with frequent rolling) will likely do more harm to bentgrass than annual bluegrass.
- At many courses annual bluegrass remains the primary turf species on putting greens. This is largely a result of our ability to keep the weaker grass alive. Greens that are predominantly annual bluegrass require lots of inputs. If the specie composition of your turf has changed dramatically as a result of winter injury, rethink your management strategies. Many of our fungicide applications are targeted at diseases of annual bluegrass such as summer patch and anthracnose. If bentgrass populations are high enough, these diseases can control the grass you want to get rid of.
- Depending on how much new bentgrass you now have in your greens, other options to consider include annual bluegrass-suppressing growth regulator treatments this year and possibly forgoing seedhead suppression treatments next spring. Suppressing seed heads is good for playability, but it also makes annual bluegrass stronger which may not be in your best interest going forward.
The winter injury many courses sustained has been painful, but it also provided many with an opportunity to establish bentgrass in greens that formerly had very little. However, getting the bentgrass established is only step number one. Now management programs need to be adjusted to favor bentgrass, which could mean not working as hard to keep annual bluegrass alive or perhaps actively trying to suppress it.
Source: Dave Oatis (doatis@usga.org)
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