Asian Soybean Rust Severity Sowed in Different Seasons

Erlei Melo Reis,Luana Maria De Rossi Belufi,Mateus Zanatta,Laércio Zambolin,Wanderlei Dias Guerra

doi:10.5539/jas.v12n10p240

Abstract

In on-farm trials, the foliolar severity of Asian soybean rust was evaluated in 44 areas, in three regions of Mato Grosso sown in December (2019) and February (2020). Several susceptible cultivars were used in different crop systems; insect pests and weeds were controlled with different management systems by the farmers. Forty soybean leaflets from four plots replications, demarcated at random in each field were taken. In laboratory foliolar severity was appraised. For rust control in the trials conducted in February, fungicides with efficiency greater than 60% were used consisting of DMIs, QoIs and SDHIs in double or triple mixtures, always adding multisites (chlorothalonil, mancozeb, copper oxychloride). The severity was greater in the fields sown in December (4.84% than in February 0.68%). The number of fungicides spraying/ha in December was 6.4 and February 4.6. It is discussed that through the use of multisites fungicides, the mutation potential in Phakopsora pachyrhizi is reduced and that the spores from areas cultivated in February, probably due to unfavorable environment, do not survive during the soybean free-period. Our results indicate that the sowing period can be changed from the end of December to February, since multisites fungicides are always used.

Highlights

Mato Grosso (MT) state is the largest Brazilian soybean producer
The on-farm trials were carried with soybean grown in the North, West and South regions of MT state, sown at the end of December 2019 and between February 1th and 15th, 2020 with a regional differential in environment and disease management, especially the multisites fungicides use according to the research recommendation in all DSS and February sowing soybean (FSS)
It has been observed in MT since 2015 growing season when was released the State Normative Instruction 002/2015, that DSSs have greater severity than those sown in February and, receiving a great number of fungicide sprayings, as scientifically documented in a previous report (Reis et al, 2020) and in the present work

Summary

Introduction

Mato Grosso (MT) state is the largest Brazilian soybean producer. In the 2019/20 season, an area of de 9.85 million hectares was cultivated, yielding 3.55 t/ha and producing 34.96 million tons (IMEA, 2020a).Soybean crop in MT begins to be sown on September 16th and ends on December 31st.In the last seasons, according to data from the Anti-rust Consortium (2020), Asian soybean rust (ASR), caused by Phakopsora pachyrhizi H. Mato Grosso (MT) state is the largest Brazilian soybean producer. In the 2019/20 season, an area of de 9.85 million hectares was cultivated, yielding 3.55 t/ha and producing 34.96 million tons (IMEA, 2020a). Soybean crop in MT begins to be sown on September 16th and ends on December 31st. In the last seasons, according to data from the Anti-rust Consortium (2020), Asian soybean rust (ASR), caused by Phakopsora pachyrhizi H. Sydow (1914), has been detected in the state since the second half of December and, in a short time, the epidemics reaches all fields

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Conclusion