TURF TALK
SURVIVING THE 2011 SUMMER: Are You Building Your Fungicide Program for the Season? By Brandon Horvath, Ph.D., Turfgrass Pathologist, The University of Tennessee
This
past summer reminds us that as the season heats up and the thermometer begins to push for the sky, we all start to wonder when our bentgrass will begin to take the nosedive. Before we can design a fungicide program that will help deliver the quality conditions we expect, though, we need to make sure our preparation for the summer is in place.
Preparation Preparations for keeping bentgrass alive in the summer begin throughout the previous winter. The key is to maintain practices that will help develop the healthiest bentgrass for the coming playing season. Cultural practices such as core cultivation, topdressing and fertilizing will help strengthen the plant. In 2004, research at the University of Georgia indicated that an increase in organic matter (OM) on high-sand-content rootzones and the change in this OM during periods of high temperature are the primary factors involved in the decline of bentgrass quality throughout the summer. The research showed that when OM increases beyond 4% by 20
TENNESSEE TURFGRASS
weight, oxygen concentrations decrease, saturated hydraulic conductivity decreases and water-holding capability increases. When temperatures increase, problems like wet wilt, scalping, soft surfaces, root loss and hightemperature injury are much more frequent. Therefore, aggressive core cultivation in preparation for the season will help improve oxygen infiltration and develop and maintain the macroporosity in the soil profile that will be critical. The research also showed that aggressive core-cultivation practices such as large hollow tines (5/8" or 1/2") are effective for 5–8 weeks, and other less-aggressive practices (small hollow tines, water injection, etc.) are effective for about 3 weeks. Topdressing is another important practice that improves the playing surface and reduces the potential for major summer losses. Topdressing’s primary role is to mix the sand rootzone with the OM that the turfgrass naturally develops during growth. Research has clearly shown that light, frequent topdressing is critical to avoid developing an organic layer that impedes the infiltration of water, increases the possibility
of black layer and develops conditions favorable for summer bentgrass decline. Topdressing is also required to fill the holes formed from core-cultivation events. Yes, topdressing is difficult on your equipment and mechanic, but regular, light topdressings on a 14- to 21-day interval will help keep OM development under control. Also consider fertility when preparing for summer’s challenges. The push for everincreasing green speed has led to a desire to restrict N inputs, with the belief that this will increase green speeds. Many research projects from across the U.S. over many years have shown that, generally, for each pound of N/1,000 ft2 applied, green speed can be expected to decrease by approximately 4". Golfers, however, are unable to detect less than a 6" difference in green speed. If golfers can’t detect it, why do something that may be detrimental to the plant? Instead, making N applications should be based more on the growth of the plant and less on the effect it may (or, more probably, may not) have on green speed. If your cultural maintenance program is
FEBRUARY/MARCH 2011 Email TTA at: tnturfgrassassn@aol.com