K.V. McCully1, M.J. Melanson1 and C. Morales1
(Partner: Horticultural Producers Association of Southern New Brunswick)
Abstract: A trial to evaluate Lexone (metribuzin) at various rates (0.33 kg/ha, 0.66 kg/ha, 0.2 kg/ha multiple applications); timings (ppi, pre, post); and application methods (post emergent - over the top; post emergent - directed to bottom third of tomato plant) was conducted on fresh market tomatoes (cv Leading Lady) to determine tomato tolerance and weed control levels. Visual ratings on tomato injury, wild radish control, ragweed control, and barnyard grass control were collected throughout the summer. Yields were also collected through seven different harvests. Results indicated that tomatoes were tolerant to Lexone regardless of the rate applied, timing, or application method. All treatments provided excellent wild radish control. Barnyard grass and ragweed control was influenced more by rate than application timing or method. As long as 0.66 kg/ha of Lexone was applied for barnyard grass and ragweed control, it did not matter when or how it was applied. Overall weed control ratings also followed the same trend where Lexone rate was the most important factor in determining the level of weed control. Yields varied from 10.3 to 23.4 t/ha for Lexone treatments, but were not considered significantly different from the hand weeded plots. This indicated that there was a lot of yield variability between the replicates for the same treatments. The highest yielding treatments were Lexone applied at 0.66 kg/ha ppi (23.4 t/ha); Lexone applied at 0.66 kg/ha applied post emergent directed to the bottom third of the tomato plants (20.6 t/ha), and Lexone 0.66 kg/ha applied pre emergence (18.2 t/ha). Overall the most effective treatment in terms of weed control, crop tolerance, vigour and yields was Lexone applied at 0.66 kg/ha pre plant incorporated (ppi). This treatment should be further evaluated to ensure consistency and accuracy.
1Potato & Horticulture Branch, NBDARD, Fredericton, NB E3B 5H1