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Integrated pest management (IPM) has always been appealing to turf managers, but in these days of reduced budgets and limited resources, there is even more attention being focused on its adoption at golf courses. Having sound cultural practices in place is the foundation for successful IPM programs, and as more than 160 superintendents and turf managers learned recently at the PACE Turfgrass Research Institute annual seminar in San Diego, researchers are making strides in developing improved cultural practice recommendations.
Soil moisture problems are frequently at the root of many IPM turf management problems, said Wendy Gelernter, Ph.D., PACE co-director and speaker. Recent PACE research indicates that dry soils play a role in a variety of turf problems, including disease.
“Most people think of fungal disease as the result of overly wet conditions, but there are several important diseases—including gray leaf spot, anthracnose and brown ring patch—that we now know are promoted when soils are too dry,” she said.
Gelernter recommends monitoring soils regularly with two meters she says no turf manager should be without. On fairways and roughs, she suggests using a soil compaction meter (available from companies such as Dickey-John, Spectrum Technologies and others for approximately $200) to probe soils.
“Take advantage of the simple, yet powerful observation that dry soils are more difficult to penetrate,” Gelernter said. “If the metal rod of the meter can be pushed (using moderate pressure) to a depth of 12 inches or more into the soil, there is sufficient moisture for good turf growth. If, on the other hand, the probe cannot be pushed further than a few inches into the soil, it is too dry."
This type of monitoring, simple as it sounds, can yield surprising and extremely helpful results to superintendents who are trying to overcome issues associated with poor irrigation distribution, variable soils, turf damage due to drought, and pest problems promoted by dry soils. Gelernter recommends monitoring as frequently as possible, and in several locations per hole. To become familiar with the use of the probe, she suggests testing it in areas of good performing turf and poor performing turf and recording the depths that are reached in each location.
On greens, where soil moisture calibration takes on an even more important role in turf performance, a more refined tool, such as the TDR 300 meter (available from Spectrum Technologies for approximately $900) is essential. By monitoring on at least a weekly basis and targeting 15 to 25 percent soil moisture on sand-based greens, turf will perform more consistently and more predictably.
But other cultural practices that PACE has studied were also found to be important to a superintendent’s pursuit of managing an IPM program. The use of sand topdressing on greens is one of them, Gelernter said. Sand dilutes organic matter, firms up the surface and improves water and gas movement through soil. Diligent use of sand suppresses anthracnose, earthworms and black turfgrass ataenius while helping to eliminate black layer; soft, bumpy and/or puffy greens; and poorly draining soils.
Low nitrogen, PACE has found, can increase the incidence of some diseases, including anthracnose, brown ring patch (Waitea), pythium root dysfunction, dollar spot, red thread and leaf rust. Conversely, high nitrogen promotes earthworms, some Rhizoctonia diseases and turf damage from nitrogen toxicity.
“Be sure to include analysis of nitrate and ammonium nitrogen in your soil tests,” Gelernter said. “We found that healthy turf grows in a range between 3 and 20 parts per million (ppm) total plant available nitrogen.”
Gelernter stresses, however, that ammonium nitrogen, which is one of the components of that total nitrogen figure, should not exceed 7 ppm.
More information on nitrogen and other soil chemical turf guidelines can be found on the PACE website: www.paceturf.org.
