Sensitivity of the pear scab fungus (Venturia nashicola) to three ergosterol biosynthesis‐inhibiting fungicides

Sensitivity patterns of Venturia nashicola strains to ergosterol biosynthesis inhibitors (EBIs) were explored in order to obtain ‘base‐line’ data. For triflumizole or bitertanol, sensitivity was examined in mycelial growth tests and comparisons were based on EC50 rather than MIC values. It was also indicated that measurements of germ‐tube length rather than observation of conidial germination or septum formation were needed to assess sensitivity to these fungicides as a rapid and simple method. Field trials were carried out to examine how fast EBIs might select for lower sensitivity in field populations of V. nashicola. Results suggested that any shifts to lower EBI sensitivity in this fungus would not proceed very quickly. It might be possible to avoid potential problems of EBI resistance and maintain the long‐term effectiveness of EBI fungicides in orchards by applying them sparingly.