Golf Course Management


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09.16 GOLF COURSE MANAGEMENT 89 affins and a food-grade emulsifier. At room temperature, it is a clear, colorless liquid com - posed of molecules with 16 to 36 carbons. The formulation has been registered in the United States (February 2009) and Canada (Janu - ary 2011) and is being investigated in other parts of the world. Label rates are 1.2% to 25% in 0.98 to 4.9 gallons of water per 1,000 square feet (4 to 20 liters/100 square meters) of grass surface. One of the features of a resistance-induc - ing compound is that it should have a weak or no direct effect on the pathogen. We tested 16 different turfgrass pathogens on culture media amended with 0% to 20% Civitas and found that there was only slight inhibition even at the highest rate. (Note that for field applica - tions of Civitas, the label rate is only 5%.) However, even this inhibition disappeared after 10 days, as growth rates after that time were similar between media with and with - out Civitas. Civitas was sprayed on turfgrass in the field and was found to have significant activity against various turfgrass diseases, with almost full disease suppression in some cases (Fig - ure 7). We also conducted tests on turfgrass grown in the laboratory in plastic containers, and found that, even when the compound was directly applied to soil without contacting the leaves, the leaves became more resistant to several fungal pathogens (Figure 8) and thus the diseased area could be reduced by 20% to 40% (1). This activity gave us the idea that the compound was activating a form of systemic resistance in the plant. The next step was to figure out how this resistance was being induced. As mentioned previously, there are two general mechanisms by which disease resistance is known to be in - duced in plants, ISR (Induced Systemic Resis- tance) and SAR (Systemically Acquired Resis- tance). There are probably other mechanisms, but these two are the best characterized at this point. They have not been well characterized in turfgrass plants, however. In other types of plants, particular genes are known to be asso - ciated with these pathways. We looked for these genes, which were first found in grass plants such as rice or wheat, in creeping bentgrass (Agrostis stolonifera). After quite a bit of searching, we found pos - sible counterparts (the scientific term is "ho- mologs") to these genes in creeping bent- grass. We used molecular biology techniques to assess whether these genes were producing Self-destruction of a plant cell Figure 5. A Figure 5. A plant cell destroys itself in an attempt to kill the invading pathogen. Fighting off the invader Fighting off the invader Figure Figure 6. A plant can successfully fight off an attacking pathogen, but sometimes must sacrifice some plant cells. ells. Figure 6. A plant can successfully fight off an attacking pathogen, but sometimes must sacrifice some plant cells. Figure 7. Field trial with 5% Civitas applied in water at 2.45 gallons/1,000 square feet (10 liters/100 square meters). The plots were inoculated with dollar spot fungus in July. This photo was taken a month later. Photos by Tom Hsiang

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