Sensitivity reduction in Blumeria graminis f. sp. hordei to triadimenol fungicide applied as barley seed treatment

Abstract

Additional keywords: Barley powdery mildew, chemical control, fungicide resistance, Hordeum vulgare.Experiments were carried out in a growth chamber with controlled temperature and photoperiod to test two populations of Blumeria graminis f. sp. hordei from Guarapuava, Paraná State, and Passo Fundo, Rio Grande do Sul State, Brazil. Treatments consisted in application of the fungicide triadimenol (Baytan 150 SC ® ) at three rates of its commercial formulation: 150, 250, 350 mL/100 Kg barley seeds. The experiments were conducted separately in a growth chamber for each population, adopting the same temperature and photoperiod. For inoculation, pots containing barley seedlings colonized by the fungus were placed among the plots. After emergence of the first symptoms, the disease severity was assessed at two-day intervals. The experiments were repeated twice for each fungus population.Reis, E. M.; Zanatta, M.; Brustolin, F.; Danelli, A.L.D. Sensitivity reduction of Blumeria graminis f. sp. hordei to triadimenol fungicide applied in barley seed treatment. Summa Phytopathologica, v.39, n.4, p.276-280, 2013. Data were expressed as area under the disease progress curve and as powdery mildew control by comparing the severity after the fungicide treatments to that of control. Data were subjected to analysis of variance and regression analysis; the area under the disease progress curve was also calculated. Comparing the data obtained in the present study with those reported in the literature and the control, the maximum value of 26.1% is considered insufficient to prevent the damages caused by the disease. The control response to the fungicide rate was significant. We can conclude that there was a reduction in the sensitivity of both B. graminis f.sp. hordei populations to the fungicide triadimenol, which explains the control failure observed in barley farms.Em experimentos conduzidos em câmara de crescimento com temperatura e fotoperíodo controlados foram testadas duas populações de Blumeria graminis f.sp. hordei oriundas de Guarapuava, PR e de Passo Fundo, RS. Os tratamentos constaram da aplicação do fungicida triadimenol (Baytan 150 SC ® ) em três doses da formulação comercial: 150; 250 e 350 mL/100 Kg de sementes de cevada. Os experimentos foram conduzidos separadamente com cada população em câmara de crescimento com o mesmo fotoperíodo e temperatura. Na inoculação posicionou-se entre as parcelas, vasos contendo plântulas de cevada colonizadas pelo fungo. Após o início do aparecimento dos sintomas, procederam-se as avaliações da severidade estimada da doença realizadas em intervalo de dois dias. Os experimentos foram repetidos Reis, E. M.; Zanatta, M.; Brustolin, F.; Danelli, A.L.D. Redução da sensibilidade de Blumeria graminis f. sp. hordei ao fungicida triadimenol aplicado em tratamento de sementes. Summa Phytopathologica, v.39, n.4, p.276-280, 2013. Palavras-chave adicionais:Controle químico, Hordeum vulgare, oídio da cevada, resistência fungicida. RESUMOduas vezes individualmente com cada população do fung...

Fungicide Resistance in Powdery Mildew Fungi

“…During the 1990s, a reduced effect of amines (fenpropimorph and fenpropidin) and several DMIs (cyproconazole, epoxiconazole, fenpropimorph, flutriafol, propiconazole, tebuconazole, and triadimenol) were reported in the same pathogen in different parts of Europe, including Hungary, England and Scotland [ 115 , 116 , 117 , 118 , 119 ] ( Table 2 ). Triadimenol resistance was also observed in 2013 in Brazilian farms, with this fungicide exhibiting only 26.1% disease control [ 120 ]. Regarding the wheat powdery mildew B. graminis f. sp.…”