Ontario Grain Farmer April/May 2022

HISTORICALLY, POST-EMERGENT applications of Callisto + Aatrex 480, dicamba (e.g. Engenia/Xtendimax) or Distinct have provided the best top-growth control of tufted vetch (Vicia cracca) in corn. A trial was conducted in 2021 to evaluate tufted vetch control with two newer herbicides, Laudis + Aatrex and Acuron as well as Lontrel XC (clopyralid), an herbicide that is effective at controlling tufted vetch, but until recently has been cost prohibitive to use in field corn (Table 1). All herbicides were applied at the 5-leaf over stage of corn and to emerged tufted vetch (at 10-15 cm in height and/or diameter). As expected, glyphosate (540 g/L) at 1.4 L/acre did not control tufted vetch (Figure 1). Marksman, Lontrel XC and Acuron all provide excellent top growth control of tufted vetch at six weeks after application (Figure 2 and Table 2). Laudis + Aatrex suppressed top growth of tufted vetch (Figure 3) but required a tank-mix with Lontrel XC for complete top-growth control. l Vetch control in corn CROP SIDE WITH... Crop side ONTARIO GRAIN FARMER 27 APRIL/MAY 2022 FIGURE 2. COMPLETE TOP GROWTH CONTROL OF TUFTED VETCH WAS ACHIEVED AT 6 WEEKS AFTER APPLICATION WITH MARKSMAN, ACURON AND LONTREL XC. FIGURE 3. TOP GROWTH WAS SUPPRESSED AT 6 WEEKS AFTER A POST EMERGENT APPLICATION OF LAUDIS + AATREX 480. FIGURE 1. TUFTED VETCH GROWTH AT SIX WEEKS AFTER AN APPLICATION OF GLYPHOSATE WAS MADE. PHOTOS AND TABLES COURTESY OF MIKE COWBROUGH. Mike Cowbrough, Weed Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs Herbicide treatment Rate/acre Relative cost/acre Glyphosate (540 mL) 1.4 L $ Marksman 1 L $ Marksman + Lontrel XC 1 L + 68 mL $$ Acuron 1.96 L $$$ Acuron + Lontrel XC 1.96 L + 68 mL $$$$ Laudis + Aatrex 480* 88 mL + 480 mL $$ Laudis + Aatrex 480* + Lontrel XC 88mL+480mL+68mL $$$ Lontrel XC 68 mL $ *Laudis + Aatrex must be applied with a methylated seed oil adjuvant and 28% UAN Herbicide treatment Visual control 2 weeks Visual control 6 weeks Glyphosate (540 mL) 20% 20% Marksman 75% 99% Marksman + Lontrel XC 80% 99% Acuron 75% 99% Acuron + Lontrel XC 95% 99% Laudis + Aatrex 480* 70% 65% Laudis + Aatrex 480* + Lontrel XC 80% 99% Lontrel XC 70% 99% TABLE 1. HERBICIDE NAME, RATE PER ACRE AND RELATIVE COST PER ACREOF TREATMENTS EVALUATED FOR THE POST EMERGENT CONTROL OF TUFTED VETCH IN CORN. TABLE 2. TOP GROWTH CONTROL OF TUFTED VETCHAT 2 AND 6WEEKS AFTER THE APPLICATION OF VARIOUS HERBICIDE TREATMENTS.

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