Effect of Formulation and Application Time of Day on Detecting Dicamba in the Air under Field Conditions

Abstract

The development of dicamba-tolerant and other auxin-tolerant crops will enable the use of these effective herbicides in soybean and cotton at application timings such as at planting or over-the-top that are not currently possible. This research examined the effect of various factors on detection of postapplication amounts of dicamba in the air under field conditions by coupling a sample collection system with advanced chemical analysis of those samples. The quantity of dimethylamine salt of dicamba that was detected within 48 hr after application was two times greater (P < 0.05) than the quantity of diglycoamine salt formulation based on field studies in 2009. Regardless of application timing, the amount of detected dicamba was greatest during the 0 to 12 hr time period after application. However, the total detected after 48 hr was less for evening applications (5 micrograms [µg]) compared with midday (17 µg) or morning (14 µg) applications based on 2010 field trials. Average ambient air temperature (and other weather variables) correlated with higher detection levels of dicamba in the air in the field.

Dicamba volatility in humidomes as affected by temperature and herbicide treatment

“…This research was conducted in the fall of 2017 and used methods from previous research by Mueller et al (2013) and Gavlick et al (2016). Expendable supplies included plastic trays to hold the sprayed material, clear plastic vented humidity domes, soil, and the aforementioned sampling media.…”

“…This research utilized air samplers previously demonstrated to be effective in collecting dicamba from the atmosphere (Mueller et al 2013). The air sampler and associated sample collection hardware are available from Hi-Q Environmental Products Co. (San Diego, CA, USA; https://www.hi-q.net/).…”

“…Others have also employed plant bioassays as indicators of dicamba activity (Egan and Mortensen 2012;Penner and Michael 2014;Sciumbato et al 2004). Although the sensitivity of these bioassays is adequate, a quantitative assessment via air sampling followed by chemical extraction and analysis may yield more direct indications of herbicide behavior (Mueller et al 2013;Mueller 2015;Ouse et al 2018). This research aimed to examine the effect of temperature, dicamba formulation, and glyphosate addition on dicamba concentrations.…”

Comparison of Simulated Drift Rates of Common ALS-Inhibiting Rice Herbicides to Florpyrauxifen-Benzyl on Soybean

“…Vapor drift, conversely, is primarily a function of volatilization that takes place after spray particles reach their intended site. This form of drift can be influenced by various abiotic factors, such as temperature and relative humidity [4,5]. Increased temperature and low humidity tend to intensify the risk for volatility to occur by increasing the amount of atmospheric space for evaporation to take place [4].…”

“…This form of drift can be influenced by various abiotic factors, such as temperature and relative humidity [4,5]. Increased temperature and low humidity tend to intensify the risk for volatility to occur by increasing the amount of atmospheric space for evaporation to take place [4]. Auxin-type herbicide residues, such as 2,4-D and dicamba, are known to be difficult to clean from spray equipment, and small amounts of these compounds could be inadvertently applied to susceptible crops if the same equipment was subsequently used to treat non-dicamba or non-2,4-D-resistant crops [6].…”