Reduction of white mold level on soybean by fungicide management strategies

Carlos Rafael Wutzki,Ayrton Berger Neto,Aguinaldo José Do Nascimento,David De Souza Jaccoud Filho,Hamilton Edemundo Tullio,Fernando Cezar Juliatti

doi:10.14393/bj-v32n3a2016-32459

Abstract

The objective of this study was to verify the efficiency of the control of white mold on soybean with the use of fungicides applied alone and in rotation, at different growth stages and in a mixture of two active ingredients at three locations: Arapoti, PR, Maua-da-Serra, PR and Pinhao, PR, Brazil. The fungicides used were carbendazim (Ca), thiophanate methyl (Tm), procymidone (Pr) and fluazinam (Fl). The experiments consisted on 17 treatments and 4 replications in a randomized block design. The analyzed variables were severity, incidence, number of sclerotia and yield. Maua-da-Serra and Pinhao presented the highest incidences (31% and 29.8% in the control, respectively). At these two locations most of treatments with fungicides decreased the incidence and production of sclerotia, when compared to control; however, no differences in terms of yield were observed. Arapoti presented the lowest incidence (15.8% in the control) where most of treatments with fungicides did not present differences for the variables incidence, production of sclerotia and yield, when compared to the control. No differences were also observed for severity in any of three locations. In conclusion, fungicides applied in soybean areas with historically white mold incidence up to 31% can reduce the disease incidence and sclerotia production levels.

Highlights

Sclerotinia sclerotiorum is a polyphagous and aggressive fungus; it hosts over 408 species of plants such as soybean, sunflower, canola, peas, beans, alfalfa, tobacco, tomato and potato (BOLAND; HALL, 1994)
Fungicides applied in soybean areas with historically white mold incidence up to 31% can reduce the disease incidence and sclerotia production levels
As well as the presence of the inoculum, the weather conditions during the flowering period are crucial in relation to the occurrence of white mold on soybean, since the flowers are used as a source of energy for the germination of ascospore, as well as there being a need for rainwater fall on plants for infection to occur (ABAWI; GROGAN, 1979; NAPOLEÃO et al, 2005)

Summary

Introduction

Sclerotinia sclerotiorum is a polyphagous and aggressive fungus; it hosts over 408 species of plants such as soybean, sunflower, canola, peas, beans, alfalfa, tobacco, tomato and potato (BOLAND; HALL, 1994). It is a disease that is difficult to control because the S. sclerotiorum fungus produces resistant structures called sclerotia, which can remain viable in the soil for periods of 5 (COLEY-SMITH; COOKE, 1971) to 10 years (FERREIRA et al, 1979). These sclerotia can germinate carpogenically and can produce up to 2 million ascospores in a period of 10 days, spreading over a distance of up to 50 m (STEADMAN, 1983). The application of fungicides may decrease the infection of soybean by disease and reduce the inoculum production for the harvest

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Conclusion