Fungicides performance on the control of asian soybean rust (Phakopsora pachyrhizi) in Goias State, Brazil.

MEYER, M. C.; NUNES JUNIOR, J.; PIMENTA, C. B.; COSTA, N. B.; GURNIERI, S.; SEII, A.; NUNES SOBRINHO, J.; VENANCIO, W. S.; GODOY, C. V.

Fungicides performance on the control of asian soybean rust (Phakopsora pachyrhizi) in Goias State, Brazil.

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Descripción

The use of fungicides remains the most important tool to Asian soybean rust (ASR) control in Brazil. The reduction of the Phakopsora pachyrhizi sensibility to triazols changed the strategy to the exclusive use of fungicides to strobilurines with triazols premix formulations. Two field trials of the Brazilian network for ASR chemical control were conducted in Goiania and Senador Canedo at Goias State in order to compare the efficacy of 17 fungicides on ASR control. The treatments were composed by two triazols, one strobilurine, one carboxanilide, and 13 premix formulations of strobilurine + triazol. The fungicides were applied twice, beginning at soybean growth stage R1 in absence of ASR symptoms (preventatively), and 21 days after first spray. The soybean cultivars were BRS 8160 RR in Goiania and BRS Valiosa RR in Senador Canedo. The area under disease progress curve (AUDPC) was calculated for each treatment based on four ASR severity evaluations from R1 to R7 soybean growth stages. The lower AUDPC and higher soybean yield were observed for almost all fungicides in premix formulations of strobilurine with triazols. The carboxanilide oxycarboxin and the triazols tebuconazole and cyproconazole were not so efficient on ASR control. The lowest reductions of soybean cycle due to ASR were observed with picoxystrobin + tebuconazole, which were 12 days later in relation to the untreated plots in Goiania and 10 days later in Senador Canedo.