A New Approach to Quantify Herbicide Volatility

David G Ouse,Curtiss J Jennings,James M Gifford,Jerome Schleier,David D Simpson,Suresh P Annangudi,Robert A Masters,Pablo Valverde-Garcia,Holger H Tank

doi:10.1017/wet.2018.75

Abstract

AbstractHerbicide 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.

Highlights

Volatilization of herbicides from the soil and leaf surfaces can result in the movement of herbicide vapor in the air
Vapor pressure can be used to compare the potential for volatility between active ingredients or formulations. 2,4-D is an example of an herbicide that can be formulated three ways, as the acid, a salt, or an ester
Three corn flats were treated. 2,4-D DMA (DMA® 4 IVM, 456 g ae L − 1 ) and 2,4-D choline (GF-2564, 456 g ae L, − 1) were sourced from Corteva AgriscienceTM, Agriculture Division of DowDuPont (Corteva Agriscience, 9330 Zionsville Road Indianapolis, IN) and dicamba diglycolamine (DGA), ClarityTM, (BASF, 100 Park Avenue, Florham Park, NJ 07932), containing 480 g ae L − 1 were used in the experiments. 2,4-D was applied at 1,120 g ae ha − 1 and dicamba was applied at 560 g ae ha − 1 to flats containing EnlistTM corn

Summary

Introduction

Volatilization of herbicides from the soil and leaf surfaces can result in the movement of herbicide vapor in the air. Plant bioassays have been used in the past to compare relative volatility of synthetic auxin herbicide formulations (Bauerle et al 2015; Breeze and Rensburg 1991; Egan and Mortensen 2012; Sciumbato et al 2004; Sosnoskie et al 2015).

Results

Conclusion