Testing the drift reduction potential of some adjuvants from renewable sources for aerial pesticide applications

Authors: Kannan, Narayanan; Fritz, Bradley - Brad; Read, Quentin; SRINIVASAN, RAJANI - Tarleton State University

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Off-target drift from aerial pesticide applications in croplands is a major source of pesticide exposure to pollinating insects. To improve spray characteristics, inert chemicals called Pesticide Adjuvants (PAs) are added to the tank mixes with pesticides. Previous studies have pointed out PAs could be as toxic as the active ingredients in the pesticide. PAs with plant-based polymers appear to be less toxic to pollinators. Our ongoing experiments have identified sodium alginate (SA) as a less toxic drift-reducing PA. Hence, SA and Fenugreek polymer (FP) was tested as drift-reducing PAs for aerial applications. Two spray experiments were carried out in the laboratory using a highspeed wind tunnel setup that mimics aerial chemical application. Droplet size was measured by a laser-based image analyzer. Spray experiment was carried out with (i) water only (W) as control and (ii) water and adjuvant (WA) as the treatment. The drift reduction potentials (DRPs) of the adjuvants were analyzed based on droplet size and the proportion of driftable droplets (less than 150 µm size). Our results indicate that SA exhibited properties that are not desirable namely - reduced the droplet size and increased the proportion of driftable particles. The FP, on the other hand, resulted in a marginal increase in droplet size and decrease in the proportion of driftable particles. Thus, neither SA nor FP can be used as adjuvants to reduce off-target drift in piloted aerial pesticide applications.

Technical Abstract: Aerial pesticide applications in croplands can be a major source of pesticide exposure to pollinating insects including off-target drift that occurs during and after application of chemical. Most pesticide applications in the lower Mississippi Delta (LMD) are carried out by piloted agricultural aircraft. Pesticide Adjuvants (PAs) are added to the tank mix to improve spray characteristics such as reducing drift. Adjuvants have been used in aerial pesticide applications for many years. PAs added to pesticides, can be as toxic as pesticide active ingredients. PAs with plant-based polymers appear to be less toxic to pollinators. Ongoing experiments have identified sodium alginate (SA) and fenugreek polymer (FP) as less toxic drift-reducing PAs. Hence, they have been tested as drift-reducing PAs for potential aerial applications using a high-speed wind tunnel experimental setup. The droplet spectrum was analyzed by Sympatec Helium-Neon Laser Optical System laser-diffraction instrument. Spray experiment was carried out with (i) water only (W) as control and (ii) water and adjuvant (WA) as treatment. The drift reduction potentials (DRPs) of the adjuvants were analyzed based on droplet size (diameters of 10%, 50% and 90% spray volume) and the proportion of driftable volume with droplets less than 150 µm. Our results indicate that SA, when added to water, reduced the droplet size instead of increasing it. Also, SA increased the proportion of driftable particles when contrasted with water which is not desirable. Although the FP polymer increased the droplet size, the reduction in driftable proportion of droplets was only marginal and that too for 1g/L concentration tested at 40° nozzle orientation only. In summary, both SA and FP at the concentrations tested, cannot be used as adjuvants to reduce off-target drift for piloted aerial pesticide applications.