Golf Course Management

DEC 2013

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

Issue link: http://gcmdigital.gcsaa.org/i/215757

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research Fungicide concentrations in verdure 200 A. Azoxystrobin 180 2000 160 1600 140 1400 120 Concentration in verdure (micrograms/gram) B. Flutalonil 1800 1200 100 1000 80 800 60 600 40 400 20 200 0 0 3 7 10 14 200 17 21 C. Metconazole 180 160 140 120 100 80 60 40 20 0 0 3 7 10 14 17 21 0 240 220 200 180 160 140 120 100 80 60 40 20 0 0 3 7 10 14 17 21 D. Pyraclostrobin 0 3 7 10 14 17 21 Days after fungicide application Figure 2. Fungicide concentrations in creeping bentgrass verdure for (A) azoxystrobin, (B) futolanil, (C) metconazole and (D) pyraclostrobin. of protection. Pyraclostrobin, metconazole and azoxystrobin had statistically similar effcacy halflife values. Azoxystrobin and pyraclostrobin, which have the same biochemical mode of action (they both are QoI) but differ in terms of phytomobility (azoxystrobin is an acropetal penetrant and pyraclostrobin is a local penetrant), did not exhibit any statistically signifcant differences based on effcacy half-life. The two fungicides classifed as local penetrants, polyoxin D and pyraclostrobin, differed with regard to their levels of brown patch control based on effcacy half-life values of 3.1 days and 5.2 days, respectively (Table 2). Quantitative residue analysis The QuEChERS multi-residue method provided acceptable chromatographic results that allowed for repeatable detection and quantifcation of fungicide residues in creeping bentgrass over a wide range of concentrations. Initial recoveries (day 0) varied greatly among the fungicides 88 GCM December 2013 (Table 2). This variation most likely refects differences in application rates (Table 1). The average amounts of fungicide detected on day 0 for azoxystrobin, futolanil, metconazole and pyraclostrobin were 127, 1,433, 128 and 200 micrograms/ gram verdure. All fungicides examined with quantitative analysis demonstrated a precipitous decline following application (Figure 2A-2D). Discussion Differences in residual efficacy Results reported here illustrate how fungicides are rapidly depleted from turf after each application. Bioassay curves were remarkably similar, except for futolanil, which was applied at a much higher rate (fve to 10 times more active ingredient) relative to the other fungicides, accounting for the inconsistency. For azoxystrobin, metconazole, polyoxin D and pyraclostrobin, residual effcacy was reduced to 50% within three to fve days. Results of previously published fungicide trials

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