FLUXAPYROXAD IN THE ASIAN SOYBEAN RUST CONTROL IN THE CERRADO BIOME

Rafael Menezes Silva De Freitas,Leonel Espósito De Lima,Roger Santos Silva,Hercules Diniz Campos,Adriano Perin

doi:10.1590/1983-21252016v29n312rc

Rafael Menezes Silva De Freitas, Leonel Espósito De Lima + Show 3 more

Open Access

https://doi.org/10.1590/1983-21252016v29n312rc

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Abstract

ABSTRACT The etiologic agent of the Asian soybean rust is the Phakopsora pachyrhizi, which causes a reduction in the photosynthetic leaf area and, consequently, in the crop yield. Chemical control is one of the main measures for its management. The objective of this work was to evaluate the efficacy and selectivity of the fluxapyroxad fungicide on controlling the Asian soybean rust, under the edaphoclimatic conditions of the Cerrado biome. The experiment was conducted in an area under no-tillage system, in the Agricultural Research Center, Rio Verde, Goias, Brazil, during the 2012/2013 crop season, using the cultivar NA7337. A randomized block experimental design was used, with twelve treatments and four replications. The treatments consisted of applications of fluxapyroxad (FX), pyraclostrobin (PT), epoxiconazole (EX) and metconazole (MZ). The average severity of the disease in the plants reached 37% in the Control. All treatments with fungicides differed from the Control. Treatments 9, 10, 11 and 12 provided the greatest rates of soybean rust control. The treatments 10, 11 and 12 had the highest thousand grain weights, and the yields of the treatments 2, 3 and 11, despite higher than the Control, were lower than the treatments 4, 5, 6, 7, 8, 9, 10 and 12, which had statistically equal yields. The increasing in yield, compared to the Control, ranged from 10.05% (pyraclostrobin, epoxiconazole + pyraclostrobin + mineral oil) to 30.55% (pyraclostrobin, pyraclostrobin + fluxapyroxad + mineral oil and pyraclostrobin + metconazole + mineral oil). The highest rates of soybean rust control were presented by fungicides containing fluxapyroxad.

Highlights

The soybean stood out in the Brazilian agribusiness exports, reaching US $ 33.8 billion from August 2013 to July 2014, an increase of 19.6% over the same period last year, despite the reduction in the average price, the volume exported increased by 24.4% (CONAB, 2014)
The increase in crop area and monoculture contributed to the increase of diseases such as soybean rust, which has as etiological agent the Phakopsora pachyrhizi Syd. & P
The results of all treatments with fungicides were different from the Control, confirming the affirmation of Dal Pogetto (2012), which says that a single fungicide spraying, regardless of crop phenological stage, is sufficient to promote a significantly higher yield compared to the Control

Summary

Introduction

The soybean stood out in the Brazilian agribusiness exports, reaching US $ 33.8 billion from August 2013 to July 2014, an increase of 19.6% over the same period last year, despite the reduction in the average price, the volume exported increased by 24.4% (CONAB, 2014). The increase in crop area and monoculture contributed to the increase of diseases such as soybean rust, which has as etiological agent the Phakopsora pachyrhizi Syd. This pathogen is commonly found in the main producing areas of soybean and, if not controlled, may cause yield losses, which are estimated in approximately 80% under optimal conditions for the fungus development, due to the rapid yellowing and premature defoliation, which hinder the formation of pods and beans (SOARES et al, 2004; YORINORI et al, 2005). Initial symptoms of soybean rust consist of small leaf spots of brown to dark brown color (PINTO, 2011). Injury and uredospore pustules may appear within 7 to 8 days (IGARASHI et al, 2014), having a short life cycle, indicating a rapid disease spread (BONDE et al, 2007)

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