While Thomas Paine’s famous quote referred to the American Revolution, as the summer wears on many golf course superintendents can relate to the literal meaning of the words. Well, at least we had a nice spring! The recent spells of high temperatures and high humidity levels have produced extraordinary disease pressure, and turf throughout the region is beginning to show the effects. Diagnostic laboratories are swamped with phone calls and submissions, and predictably, diseases are being identified in many samples. However, it is confusing and disquieting to some when disease shows up in samples of turf that have received appropriate, and perhaps even aggressive, preventive fungicide treatments. The question “how can that be” quickly is posed. In a nutshell, disease pressure simply is too high. Few pest control products ever provide 100 percent control, so when disease pressure is extraordinarily high, the percent control may drop. Additionally, there will be much more of the disease inoculum available for infection, and the turf will be more susceptible because of its stress-induced, weakened state. In short, an excellent disease control program does not guarantee success under extraordinarily high disease pressure conditions. Furthermore, stressful maintenance practices weaken the turf and leave it more susceptible to pest and disease.
So what is the solution? Control the things within your control. Reduce mowing frequency, raise cutting heights or switch to solid rollers, and above all else, manage water as closely as possible. Multiple “ultra” light syringes can help cool the turf if there is evaporative potential. Heavier applications may correct water deficiency, but wet soils heat up rapidly and this can increase turfgrass stress and disease potential.
Many courses have installed fans in recent years around pocketed greens, and this is shaping up to be another bountiful year for fan manufacturers. Normally fans are considered more of a preventive than a curative remedy, but in extreme situations they can slow and sometimes even reverse turf decline. Thus, blowers (tractor-mounted, pull-behind independent blowers, shop fans run by generators, etc.) all can help your turf in an emergency. Your golfers may not appreciate a loud, tractor-mounted blower sitting right next to a green, but they will better understand the problem when they see it, and they will appreciate your efforts in trying to remedy the situation.
Some turf managers will be tempted to implement aggressive maintenance strategies such as hollow core aeration, slit seeding, etc. While there are plenty of times when aggressive treatments are justified and likely to produce good results, now is probably not one of them. Carefully consider the time of year the weather and the potential of pushing weak turf farther into decline before reacting. Venting strategies that improve aeration and drainage without causing surface disruption or turf injury may be very helpful at this juncture. However, seeding operations are not likely to be met with much success for a few more weeks, and aggressive cultivation may kick off more stress and disease problems. It can be extremely difficult not to take action at this point, but it may be your best bet for the time being. Once temperatures moderate and seeding operations have a better chance of success, aggressive cultivation and overseeding strategies may be justified and are more likely to be successful.
So what else can be done? In areas where extensive turf thinning and loss have occurred, mowers sink deeper into the turf, and this effectively lowers the cutting heights and exacerbates the problem. As previously mentioned, switching to solid rollers and/or raising cutting heights can help. Additionally, installing numerous small plugs of healthy turf from a nursery also can help. Two inch plugs can be installed very quickly and are easy to level. If you can install enough of them, they can help elevate cutting heights and this helps to protect the remaining turf. The plugs also will spread, and will provide more protection for seedlings once seeding efforts begin. Larger plugs (4.25 inch or larger round or hex plugs) are much slower and harder to install, and they are much more visible, so give the two inch plugs a try.
Information on the USGA’s Turf Advisory Service
Contact the Green Section Staff