Spray drift and droplet spectrum from dicamba sprayed alone or mixed with adjuvants using air-induction nozzles

Guilherme Sousa Alves,Greg Robert Kruger,João Paulo Arantes Rodrigues Da Cunha

doi:10.1590/s0100-204x2018000600005

Guilherme Sousa Alves, Greg Robert Kruger + Show 1 more

Open Access

https://doi.org/10.1590/s0100-204x2018000600005

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Abstract

Abstract: The objective of this work was to evaluate the spray drift and droplet spectrum of dicamba applied alone or with potential drift-reducing adjuvants, using air-induction flat fan nozzles. Standard (XR and TT) and air-induction (AIXR and TTI) nozzles were evaluated in a wind tunnel. The adjuvants used were polymer, ammonium sulfate, vegetable oil, and phosphatidylcholine. The applications were conducted at 276 kPa pressure and 3.5 m s-1 wind speed. The droplet spectrum was measured using a laser diffraction system. Round strings were used as drift collectors, positioned perpendicularly to the wind direction, at 2, 3, 4, 5, 6, 7, and 12 m from the nozzle. Drift was calculated by quantifying, through fluorimetry, a fluorescent tracer added to each solution at 1 g L-1. Droplet spectrum and dicamba drift depend on the interaction between spray composition and nozzle type. Air-induction nozzles are more recommended for dicamba applications, especially the TTI nozzle. Polymer and ammonium sulfate increase droplet size in all nozzle types, which may reduce drift to nearby crops.

Highlights

Dicamba is an auxin-type herbicide that has been used for more than 40 years to control most of the broadleaf weeds (Behrens et al, 2007)
The polymer and ammonium sulfate adjuvants increased the droplet size across nozzle types (Figure 2)
When sprayed through TTI nozzle, which produced the coarsest droplets, vegetable oil and phosphatidylcholine reduced the Dv0.5 by 18 and 23%, respectively, in comparison to dicamba alone. These adjuvants lost their drift-reducing effect as droplet size was increased with the use of air-induction nozzles, which may indicate that these adjuvants have a great efficiency only when finer droplets are used

Summary

Introduction

Dicamba is an auxin-type herbicide that has been used for more than 40 years to control most of the broadleaf weeds (Behrens et al, 2007). 21 broadleaf weed species are known to be resistant to glyphosate, 18 of which have biotypes that are resistant to glyphosate and other herbicide types in the world (Heap, 2017). Recent introductions of genetically modified varieties of soybean and cotton which tolerate growthregulator herbicides, including dicamba, allow this compound to be used with a greater flexibility. Susceptible crops may be exposed to nontarget herbicide drift. It is well known that soybean and cotton are both naturally and highly sensitive to low-dose exposures of dicamba. Egan et al (2014) showed, in a meta-analysis study, that soybean is more susceptible to the herbicide It is well known that soybean and cotton are both naturally and highly sensitive to low-dose exposures of dicamba. Egan et al (2014) showed, in a meta-analysis study, that soybean is more susceptible to the herbicide

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