Integration of a Brassicaceae Cover Crop with Herbicides in Plasticulture Tomato

Weeds are a major constraint in tomato production, especially in the absence of methyl bromide. Field trials were conducted in 2006 and 2007 to evaluate the integrated use of a mustard 'Caliente' (a blend of brown and white mustard) cover crop with one-half and full rate PRE/POST herbicides for weed control and crop response in polyethylene-mulched tomato. Caliente was flail mowed and incorporated into the soil prior to forming beds. PRE herbicides were applied under polyethylene mulch, and POST herbicides were sprayed over the top of tomato. Full rates for S-metolachlor, halosulfuron, and trifloxysulfuron were 1,600, 27, and 7.9 g ai/ha, respectively. Caliente had no effect on weed control or tomato injury and yield. Except for large crabgrass control and tomato injury and yield, only the main effect of herbicide selection and application rate affected these parameters. Tomato injury was minimal (< 6%) from PRE- and POST-applied herbicides. S-metolachlor applied PRE provided 66% purple nutsedge, 67% yellow nutsedge, and 77% Palmer amaranth control at 4 wk after transplanting (WATP). S-metolachlor-treated plots at the full rate produced the highest marketable fruit yield among herbicide treatments, with jumbo fruit yield equivalent to the hand-weeded treatment. Trifloxysulfuron was the best POST-applied herbicide based on marketable yield and weed control. POST-applied trifloxysulfuron provided 41% purple nutsedge, 58% yellow nutsedge, and 55% Palmer amaranth control at 8 to 9 WATP. halosulfuron applied PRE controlled purple and yellow nutsedge 70 and 78%, respectively, at 4 WATP, and POST-applied halosulfuron controlled purple nutsedge 74% and yellow nutsedge 78% at 8 to 9 WATP. Halosulfuron applied either PRE or POST failed to control Palmer amaranth and large crabgrass. Greater weed control and marketable tomato yield were achieved with full rates of herbicides. This research demonstrates no additional advantage of Caliente mustard when used with herbicides in tomato. None of the PRE or POST herbicides applied alone were sufficient to maintain season-long, broad-spectrum weed control and optimum marketable yield in tomato. Therefore, integration of PRE and POST herbicides at full rates is suggested.