Does the sequence of addition of herbicide and adjuvants to the spray solution influence sicklepod control?

Maria Fernanda Tavares Ramos,Dieimisson Paulo Almeida,Marcelo Da Costa Ferreira,Renata Thaysa Da Silva Santos,Fabiano Griesang

doi:10.1590/1808-1657000542018

Maria Fernanda Tavares Ramos, Dieimisson Paulo Almeida + Show 3 more

Open Access

https://doi.org/10.1590/1808-1657000542018

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Abstract

ABSTRACT The use of adjuvants associated with herbicides aims at improving the performance of application and the consequent increase in the biological effect of the treatment. However, the sequence of product added to the sprayer tank can influence the phytosanitary spray solution. Thus, this study aimed to evaluate the control of Senna obtusifolia as a function of the sequence of addition of the herbicide aminopyralid + fluroxypyr and adjuvants in the preparation of spray solution. Two herbicide doses (1 and 2 L c.p. ha-1) associated with the adjuvants mineral oil (MO), silicone polyether copolymer (SIL), and a mixture of phosphatidylcholine and propionic acid (LEC), all in the proportion of 0.3% v v-1, with alternate addition to the spray solution to evaluate the effects of the preparation sequence. The spray solution volume considered was 150 L ha-1. Evaluations of spray solution stability were performed from the visual evaluation of homogeneity, electrical conductivity, and pH. The effect of treatment on S. obtusifolia control was measured using a scoring scale and dry matter. Correlation coefficients between the evaluations were also determined. No difference of the preparation sequence of spray solution was observed for stability, pH, and electrical conductivity, but an influence was observed on S. obtusifolia control, without changing dry matter accumulation. The treatment with the adjuvant LEC previously added to the herbicide provided a higher control rate at the highest dose, while the adjuvant SIL had the opposite effect.

Highlights

Weeds represented predominantly by dicotyledonous shrub and tree plants correspond to one of the main factors that influence pasture development, reducing forage capacity and yield gains of cattle herds (SILVA; SILVA, 2007)
A variable effect was observed for stability, pH, and electrical conductivity depending on herbicide dose, with an interaction between the evaluated treatments
Regarding S. obtusifolia control, preparation sequence resulted in differences to control the early stages of plant development, but without effect on dry matter production in the final evaluations

Summary

Introduction

Weeds represented predominantly by dicotyledonous shrub and tree plants correspond to one of the main factors that influence pasture development, reducing forage capacity and yield gains of cattle herds (SILVA; SILVA, 2007). Several species infest the pasture, including the species Senna obtusifolia, popularly known as sicklepod (LORENZI, 2014). It is an annual pioneer species, with high germination viability, dense root system, and wide tropical and subtropical distribution, occurring in most Brazilian biomes (TOPANOTTI et al, 2014; TAKANO et al, 2015). The herbicide aminopyralid + fluroxypyr is indicated for the control of several pasture weeds, including S. obtusifolia, and is recommended for post-emergence application, which must be added by 0.3% (v v-1) of adjuvants (AGROFIT, 2017). Each adjuvant has specific properties, and the proper selection is important for efficient application, given the interaction with leaf chemical composition and the way this interaction takes place (KISSMANN, 1998)

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