An analysis of the climate change effects on pesticide vapor drift from ground-based pesticide applications to cotton

Authors: Kannan, Narayanan

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2023
Publication Date: 6/16/2023
Citation: Kannan, N. 2023. An analysis of the climate change effects on pesticide vapor drift from ground-based pesticide applications to cotton. Scientific Reports. 13/1-12. https://doi.org/10.1038/s41598-023-36941-4.
DOI: https://doi.org/10.1038/s41598-023-36941-4

Interpretive Summary: Pesticides evaporating during and after application and reaching greater distances is an increasing concern to bees and other pollinators. Among the major crops cultivated in the Lower Mississippi Delta (LMD), cotton receives most of the pesticides. Therefore, an investigation was carried out to determine the likely changes in pesticide vapor drift (PVD) as a result of climate change that occurred in LMD. This will help to better understand the consequences and prepare for the future climate. 56 years of daily weather data from 1959-2014 were used for the trend analysis. Parameters related to pesticide evaporation such as evaporation potential of the pesticide, vapor accepting capacity of the air were estimated based on daily temperature and relative humidity (RH). Trends in weather data, evaporation potential and capacity of air to accept vapors were estimated using Modified Mann Kendall test, Pettitt test and Sen’s slope. Our analysis showed marginal to moderate increases in PVD during most parts of the cotton growing season as a result of climate change patterns of air temperature and RH in LMD. Estimated increased evaporation of the postemergent herbicide S-metolachlor application during the middle of July appears to be a greater concern.

Technical Abstract: Vapor drift of applied pesticides is a major concern to bees and other pollinators. Among the major crops cultivated in the Lower Mississippi Delta (LMD), cotton receives most of the pesticides per unit area. Therefore, an investigation was carried out to determine the likely changes in pesticide vapor drift (PVD) as a result of climate change. Daily values of maximum and minimum air temperature, averages of relative humidity, wind speed, wet bulb depression and vapor pressure deficit for 56 years from 1959-2014 were used for the trend analysis. Wet bulb depression (WBD), indicative of evaporation potential, and vapor pressure deficit (VPD), indicative of the capacity of atmospheric air to accept vapors, were estimated using air temperature and relative humidity (RH). The calendar year weather dataset was trimmed to the cotton growing season based on the results of a precalibrated Root Zone Water Quality Model (RZWQM) for LMD. Trend analysis covering the modified Mann-Kendall, Pettitt and Sen’s slope tests was carried out using R software. The likely changes in PVD under climate change were estimated as (a) average qualitative change in PVD for the entire growing season and (b) quantitative changes in PVD at different pesticide application periods during the cotton growing season. The analysis showed marginal to moderate increases in PVD during most parts of the cotton growing season as a result of climate change patterns. Estimated increased volatilization of the postemergent herbicide S-metolachlor applied during the middle of July appears to be a concern.