Wednesday, 9 November 2005
27

Effectiveness of Mustard Seed Meal as a Bio-Control of Dollar Spot (Sclerotinia Homeocarpa) in Creeping Bentgrass (Agrostis Stolonifera L.).

Matt J. Goddard1, John C. Sorochan2, Carl Sams1, Alan S. Windham1, and Pamela R. Baird1. (1) University of Tennessee at Knoxville, 2431 Joe Johnson Dr. Room 252, Knoxville, TN 37996-4561, (2) University of Tennessee, 2431 Joe Johnson Drive, 252 Ellington Bldg., Knoxville, TN 37996

Dollar spot, caused by Schlortinea homeocarpa F.T. Bennett, is a common turfgrass disease on golf courses, particularly, on creeping bentgrass (Agrostis stolonifera L.) putting greens. Fungicide resistance to Thiophanate-methy, iprodione, and /or propiconazole in this pathogen was observed in nine of ten golf courses sampled in Tennessee and Northern Mississippi. As a result, two studies were conducted to determine the effect of volatiles generated from Indian mustard (Brassica juncea L. Czerniak) seed meal, as a bio-control for dollar spot. In vitro results indicated that the isothiocyanates emitted by the mustard seed meal residues (MR) significantly inhibited mycelial growth by 100% at 0.05, 0.1, 1.0, 2.0, 5.0, and10.0 g MR L-1, respectively. Mycelial growth was only inhibited for 48 hours at 0.01 g MR L-1, and for 24 hours at 0.001 g MR L-1. The phytotoxicity effect of the isothiocyanates emitted by the MR was evaluated in field studies on two Crenshaw creeping bentgrass putting greens. MR were applied as a dry granule to the surface of the putting green and irrigated. Unacceptable injury occurred between the 0.5 and 1.0 g MR L-1 rates. These studies demonstrate the potentials for mustard residues as a bio-control for dollar spot on creeping bentgrass putting greens. Field studies to determine application frequencies/intervals and control of dollar spot mycelial growth in putting green conditions is warranted.

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