Isoproturon phytotoxicity to wheat (Triticum aestivum L.) is a worry for many farmers in chemical control of weeds in wheat fields, especially in subzero weather conditions. Iron chlorin e6 (ICe6), a new plant growth regulator, has been reported to enhance crop stress resistance to alleviate damage caused by stress; however, it is not clear whether ICe6 has an alleviative effect on isoproturon phytotoxicity to wheat. We determined the alleviative effect of ICe6 on isoproturon phytotoxicity to wheat, and 0.018 g ai ha−1 was the optimal dose. Meanwhile, we also studied the photosynthetic pigment content, photosynthetic parameters, oxidative stress indicators, and antioxidant enzyme activity of wheat treated with the three different treatments. We found that the photosynthetic pigment content, antioxidant enzyme activity, and photosynthesis of wheat damaged by isoproturon were significantly lower than those of the control, and the hydrogen peroxide (H2O2) and malondialdehyde (MDA) content increased. These results indicate that isoproturon stress significantly weakened the photosynthetic and antioxidant capacity of wheat. The photosynthetic pigment content, photosynthetic parameters (excluding intercellular CO2 concentration), and antioxidant enzyme activity of isoproturon+ICe6– treated wheat were significantly higher than those of isoproturon-treated wheat. The H2O2 and MDA content was significantly lower than that of isoproturon-treated wheat. These results indicate that ICe6 treatment maintained the photosynthetic pigment content of wheat and relatively improved photosynthetic capacity, allowing photosynthesis to proceed normally. ICe6 treatment also limits the decrease in antioxidant enzyme activity, effectively clearing excess reactive oxygen species and ultimately alleviating membrane lipid peroxidation damage. In summary, ICe6 not only enhances stress resistance and increases yield in crops such as soybean [Glycine max (L.) Merr.] and canola (Brassica napus L.), but also has an alleviating effect on the isoproturon phytotoxicity to wheat, which is manifested by the improvement of photosynthetic and antioxidant abilities, ultimately leading to an increase in wheat shoot height and shoot fresh weight.

The use of photosystem II (PSII)-inhibitor and/or protoporphyrinogen oxidase (PPO)-inhibitor PRE herbicides in soybean may, under adverse environmental conditions, result in early season crop injury. A field study was conducted near Brule and North Platte, Nebraska, during the 2016 and 2017 growing seasons with the objective to evaluate the impact of PRE herbicides metribuzin (PSII-inhibitor) and sulfentrazone (PPO-inhibitor) on early season soybean development, final plant stand, and yield using 22 soybean varieties adapted to southwestern Nebraska. Herbicide treatments consisted of metribuzin (560 g ai ha−1) and sulfentrazone (280 g ai ha−1) applied within 3 d after planting and a nontreated control (NTC). Sulfentrazone reduced green canopy vegetation at the V2 growth stage by 22% and final plant stand at physiological maturity by 10% compared with the NTC. The number of pods per plant was 16% higher for sulfentrazone and the number of seeds per plant was 15% and 4% higher for sulfentrazone and metribuzin compared with the NTC, respectively. Sulfentrazone and metribuzin resulted in a slightly higher yield (3%) compared with the NTC, thus no yield reduction from PRE herbicides was observed in this study. These results support other findings that sulfentrazone and metribuzin have potential to cause early-season crop injury; however, when applied according to their label recommendations and following regional agronomic management practices, this impact may not translate into soybean yield reduction while such herbicides provide effective soil residual weed control.

Effects of 0.1 M ammonium sulfate, 0.1 M potassium phosphate, and 7 g/ha of the isopropylamine salt of imazapyr {(+)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid} were evaluated on the phytotoxicity of the ammonium salt of imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} and the ammonium salt of imazethapyr {(+)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid} applied postemergence to pitted morningglory (Ipomoea lacunosa L. #3 IPOLA). While each of these salts and imazapyr applied alone had no effect, combining them with imazaquin or imazethapyr significantly increased control of pitted morningglory.

Hypocotyl and root length reduction of soybean (Glycine max) seedlings when seeds were exposed to sulfentrazone during germination were used as indices to classify cultivar response to soil-applied sulfentrazone. Seeds of ‘Stonewall’ (sulfentrazone tolerant) and ‘Asgrow 6785’ (sulfentrazone sensitive) were imbibed and allowed to germinate in 0, 1, 5, 10, and 50 ppm aqueous sulfentrazone solutions for 4 d. Hypocotyl and root lengths were reduced in both cultivars, but the reductions were greater for Asgrow 6785 than for Stonewall. Subsequently, the relative sensitivity of 28 cultivars to sulfentrazone was independently determined by two variations of the hypocotyl reduction method (both conducted in the laboratory) and by traditional full-season field evaluation. Results from laboratory and field studies were in agreement for cultivars distinctly sensitive or tolerant to sulfentrazone. However, cultivars with intermediate tolerance in laboratory studies produced variable responses in the field.

Field studies were conducted at Tifton, GA to quantify phytotoxicity of flumetsulam on peanut as influenced by application rate and timing in a weed free experiment. Flumetsulam PPI at rates up to 0.14 kg ai/ha visibly injured peanut and reduced canopy width, but injury from PPI flumetsulam at 0.07 kg/ha or less was no worse than a standard early postemergence (EPOST) treatment of bentazon (0.6 kg ai/ha) plus paraquat (0.14 kg ai/ha). Flumetsulam EPOST at rates up to 0.07 kg/ha visibly injured peanut and reduced peanut canopy width. Flumetsulam injury at rates of 0.035 kg/ha EPOST was similar to that caused by bentazon plus paraquat. Interactive effects of PPI and EPOST flumetsulam reduced early and mid-season pod and foliage biomass more than either application alone. However, peanut recovered with final yields not affected by flumetsulam, regardless of rate or time of application.

Five field experiments were conducted during 1987–89 to determine the effectiveness of using activated carbon in transplant water to reduce injury to tobacco from herbicides incorporated before transplanting. Herbicides used were dicamba, chlorimuron, atrazine, lactofen, flumetralin, pendimethalin, pebulate, and imazaquin. Activated carbon was applied in the transplant water at a rate of 9 kg ha–1 in 1987 and 18 kg ha–1 in 1988 and 1989. Measurements taken were visual stunting ratings, yield, grade index, fresh and dry weights of roots and shoots, and percent sugars and total alkaloids in cured leaves. Activated carbon consistently reduced phytotoxicity of imazaquin and chlorimuron. As much as four- and two-fold yield increases were obtained when imazaquin and chlorimuron, respectively, were applied in conjunction with activated carbon. Less consistent results were obtained in reducing the phytotoxic effects of dicamba, atrazine, and flumetralin. Phytotoxicity without activated carbon was not consistently obtained with lactofen, pendimethalin, or pebulate.

Field experiments conducted from 1987 through 1991 at the Delta Branch Experiment Station, Stoneville, MS, determined the effect of postemergence topical applications of fluometuron and MSMA on cotton yield and fruiting. Herbicide treatments applied to cotton in the cotyledon to 1-leaf growth stage were 1.12 kg ai ha-1 fluometuron plus 0.25% by vol nonionic surfactant, 2.2 kg ai ha-1 MSMA, and a combination of 1.12 kg ha-1 fluometuron and 2.24 kg ha-1 MSMA. The commercial formulation of MSMA contained nonionic surfactant. Visual injury of cotton 14 d after treatment ranged from 14 to 28% for fluometuron, 9 to 26% for MSMA, and 22 to 34% for the combination. Seed cotton yield at the first harvest was reduced by all herbicide treatments except in 1987 and for DES 119 cotton in 1990. In 1990, yield of DES 119 cotton treated with MSMA and the combination was less than the untreated control for the second harvest interval. Cotton yield from herbicide treatments at later harvests was equal to or greater than the untreated control. Only in 1988 did all treatments reduce total seed cotton yield below the untreated control. Fiber quality was not adversely affected by the herbicides. Compared to the control, plant mapping indicated that the number of sympodial branches per plant was reduced by MSMA and by the combination for DPL 50 cotton in 1990. Averaged over 4 experiment years, herbicide treatments did not reduce total bolls per plant; percentage of bolls in first, second, or outer positions; highest sympodium with two bolls; or number of sympodium with bolls in the first or second position. However, MSMA and the combination increased node number of the first sympodia by one and 1.5 positions, respectively, when compared to the control, indicating delayed maturity.

This study was conducted to determine the tolerance of three cultivars of rice (‘Lemont’, ‘Mars', and ‘Tebonnet’) to bromoxynil and triclopyr. The effects of two rates of application (the labeled rate and twice the labeled rate) at three different growth stages (two- to three-leaf stage, four- to five-leaf stage, and panicle initiation) on percent visible injury rating and percent grain yield reduction of rice were investigated. Percent visible injury ratings for triclopyr averaged across all rates and application times, were 15, 16, and 25% (LSD = 3%) for Tebonnet, Mars, and Lemont, respectively, whereas ratings for bromoxynil were 11, 8, and 7% injury (LSD = 2%). Tebonnet was more tolerant than Lemont to triclopyr with an average percent grain yield reduction, across treatments, of 6% compared with 9% for Mars and 12% for Lemont (LSD = 4%). Bromoxynil did not decrease the average yield of any of the three cultivars.

Field and greenhouse experiments evaluated the differential response of 15 green pea varieties to metribuzin applied preemergence. ‘Charo,’ ‘CMG 298,’ ‘Leah,’ ‘Scout,’ and ‘Puget’ were the most tolerant, whereas ‘Bolero’ and ‘Sundance’ were the most susceptible varieties under greenhouse conditions. Variable chlorophyll fluorescence (Fv), efficiency of photosystem II (Fv/Fmax), and leaf area were reduced sharply by metribuzin in susceptible varieties, and metribuzin susceptibility correlated highly with the reduction in shoot dry weight. Green pea varieties grown under field conditions responded to metribuzin similarly to pea varieties grown under greenhouse conditions. Metribuzin reduced shoot dry weight more in peas grown at 30/25 C than in those grown at 25/20 and 20/15 C. Also, metribuzin injured peas more when grown in soil saturated to field capacity compared to soil at 70 and 40% of field capacity.