Loss of sensitivity of Blumeria graminis f. sp. tritici to triadimenol applied as seed treatment

The objective of this work was to evaluate the loss of sensitivity of Blumeria graminis f. sp. tritici (Bgt) to the fungicide triadimenol as seed treatment. The experiments were carried out in a growth chamber with temperature and photoperiod partially controlled. A mixture of four isolates of Bgt was used and maintained on potted wheat plants in the same environment. The treatments consisted of triadimenol fungicide (150 Baytan SC ) applied at three concentrations of 150, 250, 350 mL/100 kg of seeds. The inoculation was performed by placing pots with wheat plants heavily colonized by Bgt among the experimental units. After the onset of pathogen symptoms/signs, the evaluations of foliar incidence and severity were performed. The fungicide's efficiency in controlling Bgt was lower than that reported in the literature. The sensitivity of Bgt to triadimenol was not dependent on the fungicide dose, and was not significant when compared to the control treatment with no fungicide. Maximum control was 18.1% for incidence and 31.8% for severity with no significant effect between fungicide concentrations. It can be concluded that the sensitivity to the fungicide triadimenol of the tested populations of B. graminis f. sp. tritici was lost.