Fumigants alone or in combination with herbicide for weed management in bell pepper (Capsicum annuum)

Weed management is a significant challenge faced by pepper (Capsicum annuum L.) growers in the Southeastern United States. Field experiments were implemented to study the combined effects of soil fumigants with supplemental metam potassium or S-metalochlor on weed control and bell pepper growth and yield. Experiments were designed as a completely randomized split plot with primary soil fumigant (PF) as the main plot factors and supplemental weed management (SWM) as the subplot factors. The PF included a nontreated control, 396 kg ha(-1) dimethyl disulfide (DMDS) + Chloropicrin (Pic) (79:21 w/w), and 336 kg ha(-1) 1,3-dichloropropene (1,3-D) + Pic (40:60 w/w). The SWM included a nontreated control, 475 kg ha(-1) metam potassium, and 1.06 kg ha(-1) S-metolachlor. PF and SWM treatments independently affected weed densities with no significant interactions occurring. At 12 weeks after transplanting (WATP), DMDS + Pic significantly reduced purple nutsedge (Cyperus rotundus L.) density in areas where the plastic mulch was removed after transplant to evaluate weed control, whereas 1,3-D + Pic did not significantly reduce purple nutsedge density. Neither 1,3-D + Pic nor DMDS + Pic significantly reduced broadleaf and grassy weed densities compared to the nontreated control at the end of the growing season. Metam potassium reduced purple nutsedge density by 48% compared to the nontreated control at 2 WATP but nutsedge densities did not differ at subsequent dates. S-metolachlor reduced purple nutsedge density by 50 and 69% at 4 and 6 WATP in areas where the mulch was removed after transplant compared to nontreated control. At 12 WATP, metam potassium and S-metolachlor reduced grassy weed density by 80 and 49%, respectively, and reduced broadleaf weed density by 55 and 67% compared to the nontreated control, respectively. Overall, we conclude that DMDS + Pic was more effective at reducing purple nutsedge density as compared to 1,3-D + Pic. Supplemental applications of metam potassium or S-metolachlor following the fumigation of 1,3-D + Pic or DMDS + Pic enhanced the control of purple nutsedge, broadleaves, and grasses. The evaluated treatments did not promote or adversely affect bell pepper growth or yield.