Effect of Captan Residues on Fermentation of Grapes

¹ Department of Viticulture and Enology, University of California, Davis
² Agricultural Marketing Service U. S. Department of Agriculture, Fresno, California

With the dusting schedule employed, the rainfall observed and an interval of 45 to 68 days between the last treatment and harvest, captan residues up to 2 mg/liter may occur on grapes. The smaller amounts have only a slight delaying effect on alcoholic fermentation. The larger amounts have a definite delaying effect. The residual amounts of captan from vineyard application may delay the onset of fermentation for 20 to 40 hours, but do not prevent the proper completion of fermentation once it has started. Wines prepared from captan treated grapes retained a definite cloudiness after six months storage. The cloudiness was readily removed by filtration through filter aid.