Response of Processing Tomato to Simulated Bromoxynil Drift Followed by In-Crop Metribuzin Application

摘要

Simulated drift rates of bromoxynil followed by an in-crop application of metribuzin were applied to processing tomato in eight field studies conducted from 2008 to 2010 in Ridgetown, Ontario, Canada, to determine if a synergistic interaction occurred due to the cumulative herbicide application. A transient synergistic response was observed 7 d after treatment (DAT) when bromoxynil drift rates of 8.5, 17, and 34 g ai ha(-1) were followed 3 to 5 d later by metribuzin at 250 g ai ha(-1). By 28 DAT, visible injury ratings were additive for 8.5, 17, and 34 g ha(-1) bromoxynil followed by metribuzin treatments. However, when bromoxynil at 68 g ha(-1) (20 of field rate) was followed by metribuzin, a synergistic interaction was evident and remained through harvest. Based on Colby's equation there was greater visible injury than expected at 7, 14, and 28 DAT when bromoxynil at 68 g ha(-1) was followed by metribuzin. A corresponding synergistic reduction of plant dry weight and marketable tomato yield, compared with the nontreated control, was identified. Marketable yields were expected to be 65 of the control according to Colby's equation, but observed yield reductions were 49 when bromoxynil at 68 g ha(-1) was followed by metribuzin. In general, tomato plants sprayed with metribuzin after bromoxynil drift had greater injury than treatments sprayed with bromoxynil alone.