Increasing weed control costs and limited herbicide options threaten vegetable crop profitability. Traditional interrow mechanical cultivation is very effective at removing weeds between crop rows. However, weed control within the crop rows is necessary to establish the crop and prevent yield loss. Currently, many vegetable crops require hand weeding to remove weeds within the row that remain after traditional cultivation and herbicide use. Intelligent cultivators have come into commercial use to remove intrarow weeds and reduce cost of hand weeding. Intelligent cultivators currently on the market such as the Robovator, use pattern recognition to detect the crop row. These cultivators do not differentiate crops and weeds and do not work well among high weed populations. One approach to differentiate weeds is to place a machine-detectable mark or signal on the crop (i.e., the crop has the mark and the weed does not), thereby facilitating weed/crop differentiation. Lettuce and tomato plants were marked with labels and topical markers, then cultivated with an intelligent cultivator programmed to identify the markers. Results from field trials in marked tomato and lettuce found that the intelligent cultivator removed 90% more weeds from tomato and 66% more weeds from lettuce than standard cultivators without reducing yields. Accurate crop and weed differentiation described here resulted in a 45% to 48% reduction in hand-weeding time per hectare.

Tomato is injured by low doses of 2,4-D, dicamba, quinclorac, and glyphosate. New crop varieties resistant to 2,4-D and dicamba are likely to increase use of these herbicides and may increase drift problems. There is a diverse germplasm of tomato available that includes wild relatives known to be tolerant to numerous biotic and abiotic stresses. A greenhouse and field study was conducted to investigate auxin tolerance in three wild tomato accessions (TOM199, TOM198, and TOM300) and compare them with two commercial tomato cultivars (‘Money Maker’ and ‘Better Boy’). Auxin herbicides, which included 2,4-D, dicamba, and quinclorac, were applied at doses of 11, 3, and 39 g ae ha−1, respectively. Visible injury ratings of each accession for each herbicide treatment were recorded at 7, 14, 21, and 28 d after treatment (DAT) on a 0% to 100% scale. Results indicate that all three wild tomato accessions exhibited less than 15% injury compared with 100% injury for two commercial cultivars after application of dicamba. The three wild accessions (TOM199, TOM198, and TOM300) did not show any significant reduction in plant height compared with nontreated plants. At 28 DAT, plant heights of TOM199, TOM198, and TOM300 were 25, 25, and 28 cm when treated with dicamba and 31, 30, and 31 cm nontreated, respectively. Based on these results, the identified lines can serve as a genetic resource for developing herbicide-tolerant tomato, thus minimizing or eliminating the negative impacts of drift from nonlabeled herbicides tested in this project.

Field studies were conducted to determine the effect of metam sodium and S-metolachlor applied through drip irrigation on yellow nutsedge, common purslane, bell pepper, and tomato (injury and yield) in plasticulture. Treatments consisted of weed-free, weedy, S-metolachlor alone at 0.85 kg ha-1, methyl bromide, metam sodium (43, 86, 176, and 358 kg ai ha–1) alone, and metam sodium (43, 86, 176, and 358 kg ai ha–1) followed by S-metolachlor at 0.85 kg ha–1. Metam sodium and S-metolachlor was applied preplant 2 wk before and 2 wk after transplanting (WAT) through drip irrigation, respectively. No injury was observed to bell pepper and tomato from metam sodium alone, or metam sodium fb S-metolachlor treatments. With the exception of yellow nutsedge density 15 WAT in bell pepper, herbicide program did not influence yellow nutsedge and common purslane density at 4 and 6 WAT and bell pepper and tomato yield. At 15 WAT, yellow nutsedge density was lower in treatments that received metam sodium fb S-metolachlor compared to those treatments that only received metam sodium. Drip-applied metam sodium at 176 and 358 kg ha–1 in both bell pepper and tomato provided similar control of common purslane, and yellow nutsedge, produced comparable yields, and failed to elicit any negative crop growth responses when compared to MeBr. In conclusion, metam sodium at 176 and 358 kg ha–1 fb S-metolachlor 0.85 kg ha–1 is an effective MeBr alternative for season long weed control in plasticulture bell pepper and tomato.