Abstract
Field trials were conducted in Puerto Rico and the Dominican Republic to compare the efficacy of herbicide delivery methods, and to examine the performance of herbicides on weed control in tomato (Lycopersicon esculentum Mill.). Herbicides were applied either with a piston backpack sprayer or through drip lines. Herbicide treatments were a non-treated control, metolachlor at a rate of 1 lb/acre, napropamide at 2 lb/ acre, pebulate at 4 lb/acre, and trifluralin at 0.7 lb/acre. Effects of herbicide delivery method were not significant on tomato yield, which indicated that herbicide application through drip lines performed similar to conventional preplant incorporated application. The most predominant broadleaf weeds were Portulaca oleracea L., Trianthema spp., Cleome viscose L., Boerhavia erecta L., and Amaranthus dubius Mart. and among the grasses Echinochloa colona (L.) Link., Digitaria spp., and Eleusine indica L. were the most frequent species. Weed densities at 12 weeks after treatment (WAT) revealed no significant differences among herbicides on grass and nutsedge control. However, metolachlor application decreased broadleaf weed pressure, whereas weed populations with the other herbicides were equal to that with the non-treated control. The herbicides influenced the number and weight of extra-large tomato fruits and the overall marketable yield. The highest extralarge and total tomato yields were obtained in plots treated with metolachlor. These results suggested that in heavy soils, such as the ones in the two locations in Puerto Rico and the Dominican Republic, application of preemergence herbicides through the drip lines appears to be an alternative for weed control with metolachlor in tomato fields.
