In vivo sensitivity of Phakopsora pachyrhizi to DMI and QoI fungicides

Abstract

In in vivoexperiments the sensitivity of 18 isolates of Phakopsora pachyrhizifrom several regions of Brazil to IDM fungicides (cyproconazole, epoxiconazole and tebuconazole and an IQE (pyraclostrobin) were evaluated. The assessments were based on leaflet uredia density. Inhibitory concentration (IC50) and sensitivity reduction factor were determined for all fungicide x strain interactions. Tebuconazole sensitivity reduction was detected for most fungus isolates. In contrast, there was no fungicide shift in sensitivity of the fungus to pyraclostrobin. We conclude that the control failure of soybean rust found in some farms is due to the reduced sensitivity of the fungus to the IDM fungicide and that it remains sensitive to pyraclostrobin.

A pigeonpea gene confers resistance to Asian soybean rust in soybean

“…Chemical control of ASR in Brazil began in 2002/03 after introduction of the disease in 2001. By 2004 approximately 20 million hectares were sprayed with fungicides, with a mean application of three treatments per hectare 5 . Other management strategies include a host-free period to break the continuous cycle of fungal infection and delay the onset of epidemics.…”

Sensitivity of two isolates of Phakopsora pachyrhizi to dithiocarmamate, chloronitril, triazoles, strobilurins, and carboxamides fungicides

“…Several methods have been described to measure the sensitivity of a fungus to a given fungicide, or to monitor its sensitivity reduction or loss, or even the fungitoxicity of a chemical (FRAC, 1991;RUSSEL, 2004;BLUM, 2009;BLUM;REIS, 2013;DEUNER;ZANATTA, 2015).…”

Contribution of soybean seed treatment with Fluquinconazole to manage yield losses caused by Phakospora pachyrhizi using meta-analysis

“…respectively. According to changes observed in the behaviour of the P. pachyrhizi and the lower efficiency of triazoles cited by Godoy (2012) and a significant reduction in strobilurins efficacy cited by Godoy (2011), Barbosa et al (2013) and Reis et al (2015) the integration of foliar spray and seed treatment may be benefits in management of soybean rust, through reducing the action of initial inoculum and delaying development, as presented by Goulart et al (2011Goulart et al ( , 2015 using only fluquinconazole in TS was observed delay in the progression in severity and defoliation caused by rust.…”

“…Changes observed in the behaviour of this fungus and the lower efficiency of triazoles (Godoy, 2012) and a significant reduction in strobilurins efficacy (Godoy, 2011;Barbosa et al, 2013;Reis et al, 2015) has stimulated reviews and the testing of alternative methods of control in recent harvests. Seed treatment (ST) with fungicides was then tested as a way of managing P. Pachyrhizi in 2004 (Araujo et al, 2012).…”