Disease has been a popular topic on Turf Advisory Service visits and in several recent conversations with golf course superintendents. Mild temperatures and increased relative humidity have created favorable disease conditions throughout the Florida Region. Cool, foggy mornings are particularly favorable, especially if the turf is green and lush.
Recently, the most prevalent disease has been leaf spot caused by Helminthosporium (Dreschlera sp.). Pythium blight and brown patch also can occur on putting greens at this time of year. Luckily we have only learned of one suspected outbreak of Rhizoctonia zeae in our region. This pathogen becomes active in late summer/early fall and recovery is difficult as temperatures drop in the fall.
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| Mini "frog-eye" patches from suspected Rhizoctonia zeae. |
There are other factors that cause turf thinning on putting greens at this time of year, and one of the most prevalent is over-watering. Water loss from soil and turf decreases during fall and winter months, and saturated soil conditions occur if the same amount of water is applied as in periods of active turf growth. The result is a buildup of carbon dioxide gas and depleted oxygen in the soil, causing turf decline and a thinning of the turf canopy. Algae quickly fill these voids, worsening turf quality. Shade and traffic are major concerns at this time of year, as the sun sets lower in the horizon and increased golf rounds occur. It is important to determine whether your disease is caused by a pathogen (biotic) or some other environmental or mechanical stress (abiotic), so that appropriate control measures can be applied. For more information on this important topic, read the aticle, Infection, Disease, and Symptoms, written by Steven Kammerer in the January/February 2007 Green Section Record.
If a biotic disease is suspected, it is necessary to correctly diagnose the pathogen causing the disease. Turf samples should be evaluated by a qualified diagnostic lab prior to fungicide treatments. The University of Florida has a revamped turf diagnostic laboratory that provides reliable information in a timely manner. Sample submittal information is available at: http://turf.ufl.edu/turf_diagnosis/index.html. It is very important to correctly diagnose the pathogen for a reliable fungicide program to be implemented. Sometimes a broad-spectrum fungicide is necessary immediately to save the turf, but I recommend sending in a sample just prior to fungicide application to plan future treatments.
Source: Todd Lowe, tlowe@usga.org or 941-828-2625
