Herbicide active ingredients, formulation type, ambient temperature, and humidity can influence volatility. A method was developed using volatility chambers to compare relative volatility of different synthetic auxin herbicide formulations in controlled environments. 2,4-D or dicamba acid vapors emanating after application were captured in air-sampling tubes at 24, 48, 72, and 96 h after herbicide application. The 2,4-D or dicamba was extracted from sample tubes and quantified using liquid chromatography and tandem mass spectrometry. Volatility from 2,4-D dimethylamine (DMA) was determined to be greater than that of 2,4-D choline in chambers where temperatures were held at 30 or 40 C and relative humidity (RH) was 20% or 50%. Air concentration of 2,4-D DMA was 0.399 µg m−3at 40 C and 20% RH compared with 0.005 µg m−3for 2,4-D choline at the same temperature and humidity at 24 h after application. Volatility from 2,4-D DMA and 2,4-D choline increased as temperature increased from 30 to 40 C. However, volatility from 2,4-D choline was lower than observed from 2,4-D DMA. Volatility from 2,4-D choline at 40 C increased from 0.00458 to 0.0263 µg m−3and from 0.00341 to 0.025 µg m−3when humidity increased from 20% to 50% at 72 and 96 h after treatment, respectively, whereas, volatility from 2,4-D DMA tended to be higher at 20% RH compared with 50% RH. Air concentration of dicamba diglycolamine was similar at all time points when measured at 40 C and 20% RH. By 96 h after treatment, there was a trend for lower air concentration of dicamba compared with earlier timings. This method using volatility chambers provided good repeatability with low variability across replications, experiments, and herbicides.

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Since their introduction in 1996, glyphosate-tolerant crops have been widely adopted in the United States. The adoption of the glyphosate-tolerant cropping system and the increasing use of glyphosate have contributed to the development of glyphosate-resistant weeds and the increased prevalence of hard-to-control weeds. Dow AgroSciences is developing the Enlist Weed Control System to address this problem. This herbicide-tolerant trait technology provides robust tolerance to 2,4-dichlorophenoxyacetic acid (2,4-D) in corn, soybeans, and cotton. It will be combined with other traits that provide glyphosate tolerance. Concurrent with the development of the trait technology, Dow AgroSciences is developing new 2,4-D-based products to be used in this weed control system. Enlist Duo herbicide (PremixED), a premix formulation that combines 2,4-D choline salt with glyphosate, employs novel formulation technology that substantially reduces the potential for off-target movement through ultralow volatility and minimized potential for spray droplet drift. PremixED also provides greater spray tank stability and compatibility than current tank mixes of 2,4-D with glyphosate. The herbicidal efficacy of the new formulation is comparable to that of an equivalent tank mixture.

A typical agricultural chemical spray process involves atomizing a liquid stream of diluted pesticide solution through hydraulic spray nozzles that inherently produce a wide spectrum of spray droplet sizes. Finer droplets have higher potential for off-target movement or drift, which is of concern due to its potential impact on neighboring crops and livestock, sensitive ecological resources, and human health. Research by the Spray Drift Task Force and others has demonstrated that, although spray nozzle selection and application parameters are the key factors to produce the desired droplet size spectrum, the physical properties of the spray solution have significant effects on the droplet size distribution for various kinds of nozzles. One of these properties of many spray fluids is the inclusion of an oil phase in the form of an emulsion. The effect of oil-in-water emulsions on the spray droplet size distribution has been demonstrated by previous work. However, the mechanisms of this effect are largely unknown. In this study, a method to model this effect was proposed. A characteristic dimensionless number for connecting the bulk spray properties and the microscopic emulsion droplet properties was defined as the ratio between the emulsion recovery time and the spray atomization time. This study will help in the design of agricultural spray nozzles and the optimization of anti-drift spray additives.