Effect of Herbicide-Fungicide Tank-Mix Combinations on Weed Control and Tomato Tolerance

Tank-mix applications of fungicides/bactericides and herbicides can improve production efficiency, however there is little information on the effect of herbicide and strobilurin fungicide tank mixes on processing tomato in Ontario. A total of six field trials were conducted over a three year period (2004-2006) in Ontario to study the effect of rimsulfuron, thifensulfuron-methyl, or metribuzin in combination with azoxystrobin and pyraclostrobin on processing tomato. Under weed-free conditions, there was visual injury of processing tomato with postemergence applications of thifensulfuron-methyl+pyraclostrobin, though total yield was unaffected. None of the other herbicide-fungicide mixtures caused visual injury, delayed maturity or reduced yield in tomato. In the absence of hand-weeding, rimsulfuron, thifensulfuron-methyl, and metribuzin could be tank-mixed with either azoxystrobin or pyraclostrobin without a reduction in weed control. Application of thifensulfuron-methyl, rimsulfuron and metribuzin with azoxystrobin, or rimsulfuron and metribuzin with pyraclostrobin could provide tomato growers with a single-pass treatment for the control of troublesome weeds and diseases in Ontario. It is recommended that thifensulfuron-methyl not be tank-mixed with pyraclostrobin due to the potential for injury.