Wood vinegar, a product of pyrolysis, can induce phytotoxicity on plants when applied at an adequate rate and concentration. The objective of this research was to investigate wood vinegar obtained from the pyrolysis of apple tree branches for weed control in dormant zoysiagrass. In environment-controlled growth chambers, white clover visual injury and shoot mass reduction were evaluated and compared to the nontreated control after wood vinegar application at 1,000, 2,000, or 4,000 L ha−1 under 10 C or 30 C temperature conditions. Averaged across rates, wood vinegar rapidly desiccated white clover and caused 83% and 71% visual injury at 10 C and 30 C, respectively, at 1 d after treatment (DAT). Averaged across temperatures, wood vinegar at 1,000, 2,000, and 4,000 L ha−1 reduced white clover shoot mass by 56%, 81%, and 98% from the nontreated control at 10 DAT, respectively. In field experiments, weed control increased as wood vinegar rates increased from 1,000 to 5,000 L ha−1 in dormant zoysiagrass. The effective application dose of wood vinegar required to provide 90% control (ED90) of annual fleabane, Persian speedwell, and white clover was determined to be 2,450, 2,300, and 4,020 L ha−1, respectively, at 2 wk after treatment. Turf quality did not differ among the wood vinegar treatments and the nontreated control when zoysiagrass completely recovered from dormancy. Overall, results illustrate that wood vinegar resulting from the pyrolysis of apple tree branches can be used as a nonselective herbicide in dormant turfgrass, offering a new nonsynthetic herbicide option for weed control in managed turf.

Glyphosate-resistant giant ragweed is one of the most competitive weeds of agronomic crops in the United States. Early emergence and rapid growth rate makes giant ragweed a competitive weed early in the season and reduces crop yields. Therefore, early spring control of giant ragweed using a preplant herbicide is critical. Glufosinate is an alternative POST herbicide for weed control in glufosinate-resistant soybean. Field experiments were conducted at David City, NE, in 2012 and 2013 to evaluate the efficacy of preplant herbicides followed by glufosinate applied alone or in tank mixes for control of glyphosate-resistant giant ragweed in glufosinate-resistant soybean. Preplant treatments containing 2,4-D, flumioxazin, glufosinate, paraquat, saflufenacil, and sulfentrazone provided 79 to 99% control of giant ragweed 21 d after treatment (DAT), and subsequent application of glufosinate alone or in tank mixes resulted in 90 to 99% control at 21 DAT. Preplant application of S-metolachlor plus metribuzin or chlorimuron, flumioxazin plus thifensulfuron followed by glufosinate resulted in < 40% control of giant ragweed, and soybean yields were < 870 kg ha−1. Although statistically comparable to several other treatments, preplant application of 2,4-D or saflufenacil tank mixes followed by glufosinate resulted in the highest level of control (> 97%) and soybean yield (2,624 to 3,378 kg ha−1). This study confirms that preplant herbicide options are available for control of glyphosate-resistant giant ragweed, and a follow-up application of glufosinate will provide season-long control in glufosinate-resistant soybean.

Field studies were conducted to determine if mesotrione alone or in combinations with other corn herbicides would control horseweed and other winter annual weeds associated with no-till corn. Mesotrione alone controlled horseweed 52 to 80% by 3 wk after treatment (WAT); however, by 7 WAT control diminished to between 37 to 68%, depending on mesotrione rate. Mesotrione at 0.16 kg ai/ha plus atrazine at 0.28 kg ai/ha controlled 99% of horseweed and annual bluegrass and 88% of yellow woodsorrel. Combinations of mesotrione at 0.16 kg/ha plus acetochlor at 1.79 kg ai/ha plus 1.12 kg ai/ha glyphosate (trimethylsulfonium salt of glyphosate) or 0.7 kg ai/ha paraquat provided 93% or greater control of all three weed species. Glyphosate alone also controlled all weed species 97 to 99%, while paraquat alone provided 99% control of annual bluegrass, 72% control of horseweed, and 36% control of yellow woodsorrel. Mixtures of paraquat plus acetochlor improved control of horseweed (93%) and yellow woodsorrel (73%) over control with either herbicide applied alone.

Giant ragweed is one of the most competitive annual broadleaf weeds in soybean production fields in the midwestern United States and eastern Canada because of its early emergence, rapid growth rate, high plasticity, and resistance to glyphosate and acetolactate synthase inhibitors. Therefore, early-season management of giant ragweed is critical to avoid yield loss. The objectives of this study were to evaluate control of glyphosate-resistant giant ragweed through the integration of preplant tillage or 2,4-D; PRE or early POST (EPOST) followed by (fb) late POST (LPOST) herbicide programs with or without preplant tillage or 2,4-D; and their effect on soybean injury and yield. A field study was conducted in 2013 and 2014 in David City, NE in a field infested with glyphosate-resistant giant ragweed. Preplant tillage or 2,4-D application provided > 90% control of glyphosate-resistant giant ragweed 14 d after preplant treatment. Giant ragweed control and biomass reduction were consistently > 90% with preplant tillage or 2,4-D fb sulfentrazone plus cloransulam PRE or glyphosate plus cloransulam EPOST fb glyphosate plus fomesafen or lactofen LPOST compared with ≤ 86% control with same treatments without preplant tillage or 2,4-D. PRE or EPOST fb LPOST herbicide programs preceded by preplant treatments resulted in giant ragweed density < 2 plants m−2 and soybean yield > 2,400 kg ha−1 compared with the density of ≥ 2 plants m−2 and soybean yield < 1,800 kg ha−1 under PRE or EPOST fb LPOST herbicide programs. The contrast analysis also indicated that preplant tillage or 2,4-D fb a PRE or POST program was more effective for giant ragweed management compared with PRE fb POST herbicide programs. Integration of preplant tillage would provide an alternative method for early-season control of giant ragweed; however, a follow up application of herbicides is needed for season-long control in soybean.