Sensitivity of the causative agent of net blotch of barley (Pyrenophora teres) to a two-component fungicide based on triazole and strobilurine classes

The study was conducted to investigate the sensitivity of net blotch of barley (pathogen – Pyrenophora teres Drechsler) to two-component fungicides based on triazole and strobilurine classes. The work was carried out on intact barley plants and in pure culture of the fungus using four preparations (Amistar Extra, SC, Amistar Gold, SC, Baliy, MC, Delaro, SC) and five treatment options with different application rates from those recommended by the manufacturers (0 (control without fungicide), 50%, 100% (manufacturers’ recommended rate), 150%, 200%). It was found that the sensitivity of the P. teres fungus varied significantly depending on the active ingredient in the toxicant and the mechanism of interaction with the preparation – in vivo (indirect) or in vitro (direct). When the plants were treated with the doses recommended by the manufacturers, the minimum biological efficacy was found after treatment with the fungicide Delaro, SC – 76.3% (based on protioconazole (175 g/l) and trifloxystrobin (150 g/l)), the maximum biological efficacy was found after treatment with Baliy, MC – 83.1% (based on azoxystrobin (120 g/ l) and propiconazole (180 g/l)). When fungicides were applied to cups with a nutrient medium, the growth of fungal colonies was slowed down in all experimental variants, the maximum biological efficacy values were found after application of Amistar Gold, SC – 98.8% (on the basis of azoxystrobin (125 g/l) and diphenoconazole (125 g/l)), Delaro, SC – 98.4% (based on based on protioconazole (175 g/l) and trifloxystrobin (150 g/l)); minimum values were found when applying Amistar Extra, SC – 38.8% (on the basis of azoxystrobin (200 g/l) and ciproconazole (80 g/l)). The introduction of all preparations into the nutrient medium caused excessive structuring and pathological differentiation of P. teres fungus mycelium, and an acceleration of colony growth phases was observed on the medium with fungicides in comparison with the control variant. The introduction of Amistar Gold, SC, Delaro, SC, and Baliy, MC preparations completely inhibited sporulation. The conducted studies provided new knowledge on the changes in morphological and cultural characteristics of the regional population of P. teres under the action of fungicides of the triazole and strobilurine classes and its sensitivity to toxicants.

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