Effect of Pesticide Addition Sequence on the Preparation of Phytosanitary Spray Solutions

M.F.T Ramos,R.T.S Santos,J.F.D Vechia,D.P Almeida,M.C Ferreira

doi:10.1590/s0100-83582019370100075

M.F.T Ramos, R.T.S Santos + Show 3 more

Open Access

https://doi.org/10.1590/s0100-83582019370100075

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Abstract

ABSTRACT: The addition of adjuvants to herbicide solutions is aimed at preserving or enhancing the biological effect of treatment. However, it is commonly performed without knowledge of the physicochemical interactions between products. This study aimed to assess the effects of different addition sequences of the herbicide aminopyralid + fluroxypyr and adjuvants in the preparation of phytosanitary spray solutions on the surface tension and contact angle. Two experiments were carried out with herbicide doses of 1 and 2 L ha-1 associated with the adjuvants mineral oil (MO), silicone-polyether copolymer (SIL), and a mixture of phosphatidylcholine (lectin) and propionic acid (LEC), all at a proportion of 0.3% v v-1. The application rate was 150 L ha-1. Surface tension was measured by the pendant droplet method. Contact angle was measured on the adaxial and abaxial surfaces of leaves of the pasture weed Senna obtusifolia and parafilm. Preparation sequence did not change the contact angle on any of the analyzed surfaces at a dose of 1 L ha-1 of herbicide. For the dose of 2 L ha-1, the adjuvants SIL and LEC showed a higher spreading when previously added to the herbicide. MO resulted in a higher spreading when added after the herbicide, with higher surface coverage. Therefore, the preparation sequence influences the dispersion of phytosanitary spray solutions on targets.

Highlights

Product addition sequence to the sprayer tank during the preparation of spray solution with herbicides and adjuvants is important to avoid possible problems with phytointoxication, treatment ineffectiveness or damages to the sprayer equipment due to potential incompatibilities (Cessa et al, 2013).Agricultural adjuvants are compounds added to formulations or spray solutions directly into the sprayer tank to modify their physicochemical properties
Considering the lack of information on the technology of pesticide application in pastures, this study aims at contributing to the decision-making of farmers regarding the most appropriate combination between adjuvants and herbicide, as well as the correct product addition sequence to the phytosanitary spray solution since it is possible that adjuvant addition alternation interferes with the surface tension and, droplet spreading on leaf surfaces
The study of characteristics of surface tension and contact angle as a function of the preparation sequence of the addition of herbicide and adjuvant to the spray solutions showed no differences for the variable surface tension

Summary

Introduction

Agricultural adjuvants are compounds added to formulations or spray solutions directly into the sprayer tank to modify their physicochemical properties These compounds may contribute to the compatibility of products in the sprayer tank and improve the performance of agricultural applications, influencing the viscosity, surface tension, contact angle, pH, electrical conductivity, and retention and droplet deposition (Prado et al, 2016; Cunha et al, 2017). Surface tension is the force on fluid surfaces, and its reduction in the spray solution provides a higher spreading capacity of droplets (Silva et al, 2006) This property interferes with the amount of herbicide retained on the leaf surface and, together with leaf chemical composition, how this interaction occurs (Prado et al, 2016). Adjuvants differ significantly from each other in reducing the surface tension and contact angle, factors relevant to droplet formation and target coverage, which should be carefully considered for an appropriate selection (Li et al, 2016)

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