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Spatial and temporal distribution of fungicides applied to creeping bentgrass
K. R. HOCKEMEYER (1), R. X. Latin (1). (1) Purdue University, West Lafayette, IN, U.S.A.

Turf managers often rely on fungicides to limit damage caused by root diseases. Since fungicides do not move basipetally, they can only be effective if fungitoxic concentrations can be delivered to the rhizosphere. This research focused on the distribution of modern fungicides in verdure, thatch, sand, and roots of creeping bentgrass maintained as a putting green. Fungicides (azoxystrobin, propiconazole, pyraclostrobin, thiophanate-methyl) were applied to replicate field plots in a water volume of 815 L ha-1. Plots were sampled over time (0, 3, 7, 10, 14, 17, 21 days after application) by extracting cores measuring 2 cm diameter by 3.8 cm deep. Cores were separated into verdure/thatch, sand, and roots before quantitative determination (liquid chromatography, triple quadrupole mass spectrometry) of fungicide residues over time. Fungicide residues in verdure/thatch declined steadily over time and support previously reported results describing fungicide depletion. Fungicides were detected in roots and sand within 5 hours post application, although at very low (1-15 ppm) concentrations. Residues in roots and sand remained at low levels throughout the course of the experiment. Fungicides differed with respect to amounts recovered in each section. These results describe fungicide depletion in the rhizosphere over time.

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