There is zero tolerance for dicamba and dicamba metabolite residue in tomato (Solanum lycopersicum L.) fruit following exposure to dicamba. Field trials were conducted in 2020 and 2021 to determine the persistence of dicamba and metabolite [5-hydroxy dicamba and 3,6-dichlorosalicylic acid (DCSA)] residue in processing tomato shoots and fruits. Dicamba was applied 49 days after transplanting at 0, 0.53, 5.3, and 53 g ae ha−1. Tomato plants were harvested 5, 10, 20, 40, and 61 days after treatment (DAT). No 5-hydroxy dicamba was recovered from any sample. In 2020, the DCSA metabolite was detected from tomato shoot tissue when dicamba was applied at 53 g ha−1 rate at 0 (14 µg kg−1), 5 (3 µg kg−1), and 20 DAT (5 µg kg−1) and in tomato fruit tissue at 53 g ha−1 at 20 (2 µg kg−1) and 61 DAT (2 µg kg−1). In 2021, DCSA was not detected from tomato shoot or fruit tissues at any harvest date. By 5 DAT, dicamba was only detected from tomato shoot tissues treated with 53 g ha−1. At 0 DAT, dicamba residue was detectable only from tomato fruit on plants treated with 53 g ha−1. Tomato fruit dicamba residue from plants treated with 5.3 g ha−1 had a predicted peak of 19 µg kg−1 at 11.3 DAT. Tomato fruit dicamba residue from plants treated with 53 g ha−1 decreased from 164 to 8 µg kg−1 from 5 to 61 DAT. Furthermore, this study confirms that dicamba is detectable in tomato fruits 61 DAT following exposure to 5.3 or 53 g ha−1 dicamba. Growers who suspect dicamba exposure should include tomato fruit tissue with their collected sample or sample tomato fruits separately.

Morningglories (Ipomoea spp.) are among the most troublesome weeds in cucurbits in the United States; however, little is known about Ipomoea spp. interference with horticultural crops. Two additive design field studies were conducted in 2020 at two locations in Indiana to investigate the interference of ivyleaf morningglory (Ipomoea hederacea L.) and pitted morningglory (Ipomoea lacunose L.) with triploid watermelon Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. Immediately after transplanting watermelon, Ipomoea spp. seedlings were transplanted into the watermelon planting holes at densities of 0 (weed-free control), 3, 6, 12, 18, and 24 per 27 m2. Fruit was harvested once a week for four weeks, and each fruit was classified as marketable (≥ 4 kg) or non-marketable (<4 kg). One week after the final harvest, aboveground biomass samples were collected from 1 m2 per plot and oven-dried to obtain watermelon and Ipomoea spp. dry weight. Seed capsules and the number of seeds in 15 capsules were counted from the biomass sample to estimate seed production. Ipomoea spp. densities increasing from 3 to 24 per 27 m2 increased marketable watermelon yield loss from 58 to 99%, reduced marketable watermelon fruit number 49 to 98%, reduced individual watermelon fruit weight 17 to 45%, and reduced watermelon aboveground biomass 83 to 94%. Ipomoea spp. seed production ranged from 549 to 7,746 seeds m-2, greatly increasing the weed seed bank. Ipomoea spp. hindered harvest due to their vines wrapping around watermelon fruits. The most likely reason for watermelon yield loss was interference with light and consequently less dry matter being partitioned into fruit development due to less photosynthesis. Yield loss was attributed to fewer fruit and the weight of each fruit.

Three dose-response trials were performed in 2020 and 2021 at two Indiana locations: the Southwest Purdue Agricultural Center (SWPAC) and the Pinney Purdue Agricultural Center (PPAC), to determine the tolerance of two Jack O’Lantern pumpkin cultivars to fomesafen applied preemergence. The experiment was a split-plot arrangement in which the main plot was the fomesafen rate (0, 280, 560, 840, and 1,220 g ai ha−1), and the subplot was the pumpkin cultivar ('Bayhorse Gold’ and 'Carbonado Gold'). As the fomesafen rate increased from 280 to 1,120 g ha−1, the predicted pumpkin emergence decreased from 85 to 25% of the non-treated control at SWPAC-2020, but only from 99 to 74% at both locations in 2021. The severe impact on emergence at SWPAC-2020 was attributed to rainfall. Visible injury included bleaching and chlorosis due to the herbicide splashing from the soil surface onto the leaves and included stunting, but injury was transient. As the fomesafen rate increased from 280 to 1,120 g ha−1, the predicted marketable orange pumpkin yield decreased from 95 to 24% of the non-treated control at SWPAC-2020 and 98 to 74% at PPAC-2021. Similarly, the predicted marketable orange pumpkin fruit number decreased from 94 to 21% at SWPAC-2020 and 98 to 74% at PPAC-2021. Fomesafen rate did not affect marketable orange pumpkin yield and fruit number at SWPAC-2021 and marketable orange pumpkin fruit weight at any location year. Overall, the fomesafen rate of 280 g ha−1 was safe for use preemergence in the pumpkin cultivars 'Bayhorse Gold’ and 'Carbonado Gold’ within one day after planting, but there is a risk of increased crop injury with increasing rainfall.

Trials were conducted in two experimental runs at the Purdue University Horticulture Greenhouses, West Lafayette, IN to determine ‘Redefined Murray Mitcham’ peppermint tolerance to tiafenacil. Established peppermint in 20 cm diameter polyethylene pots was subjected to a simulated harvest by removing aboveground biomass at the substrate surface; then tiafenacil was applied at 0, 25, 50, 100, and 200 g ai ha-1. Visible crop injury, height, and aboveground dry biomass data were subjected to regression analysis to generate predictive models. At 2 weeks after treatment (WAT), peppermint injury increased from 63 to 86% and 25 to 76% in experimental runs 1 and 2, respectively, as tiafenacil rate increased from 25 to 200 g ha-1. At 4 WAT injury increased from 0 to 63% and 4 to 37% in experimental runs 1 and 2, respectively, as tiafenacil rate increased from 25 to 200 g ha-1. By 7 WAT (both experimental runs), injury increased from 0 to 17% as tiafenacil rate increased from 25 to 200 g ha-1. At 4 WAT, height decreased from 23.0 to 8.6 cm and 17.6 to 10.3 cm in experimental runs 1 and 2, respectively, as tiafenacil rate increased from 0 to 200 g ha-1. At 7 WAT, height decreased from 28.1 to 21.4 cm as tiafenacil rate increased from 0 to 200 g ha-1. Aboveground dry weight of the non-treated check was 20.3 g pot-1 and decreased from 19.3 to 7.0 g pot-1 as tiafenacil rate increased from 25 to 200 g ha-1. Despite acute necrosis, injury from tiafenacil at lower rates was not persistent. The proposed 1X rate of tiafenacil for peppermint, 25 g ha-1, resulted in < 4% injury 4 and 7 WAT and only a 3% reduction in plant height and 4.7% reduction in above ground dry weight compared to the non-treated check.

A dose-response trial was conducted in two experimental runs at the Purdue University Horticulture Greenhouses, West Lafayette, IN, in 2021/2022 to determine the effect of mesotrione rate on simulated dormant ‘Redefined Murray Mitcham’ peppermint. Peppermint was established in 20-cm diameter polyethylene pots, then the peppermint was harvested and pots were placed in a cooler (4 C) for one month. Potted peppermint plants were removed from cold storage and treated with one of five mesotrione rates: 0 (non-treated control), 53, 105, 210, or 420 g ai ha-1. As mesotrione rate increased from 53 to 420 g ai ha-1, predicted peppermint injury increased from 35% to 80% at 2 weeks after treatment (WAT), 36% to 95% at 4 WAT, 9% to 95% at 6 WAT, and 8% to 90% at 8WAT; and peppermint height decreased from 74% to 42% of the non-treated control (7 cm) 2 WAT, 74% to 17% of the non-treated control (20 cm) 4 WAT, 81% to 15% of the non-treated control (28 cm) 6 WAT, and 88% to 19% of the non-treated control (37 cm) 8 WAT. Mesotrione rates from 53 to 420 g ai ha-1 reduced peppermint dry weight from 40 to 99%, respectively. Results from this experiment showed that mesotrione applied even at half of the recommended field use rate for corn (53 g ai ha-1), was not safe for peppermint due to reduction in aboveground biomass.