Sensitivity of Epiphytic Fungal Isolates from Banana to a Commercial Mixture of Two Demethylation Inhibitors Propiconazole and Difenoconazole

Banana is one of the most important fruit crops globally. To protect bananas from devastating fungal diseases, demethylation inhibitors (DMIs) such as difenoconazole and propiconazole are commonly used as fungicides. However, their potential impact on non- target of the fungicide spray on the epiphytic fungi present on banana leaves, remains poorly understood. This study was conducted to determine the sensitivity of thirty-eight epiphytic fungi isolated from sigatoka-infected banana leaves to a commercial product, Armure 300 EC, containing two DMIs, propiconazole and difenoconazole, using a fungicide-amended potato dextrose agar (PDA) plate assay. Differential sensitivity was found in test isolates. Out of thirty non-target fungal isolates, nineteen of which were classified as sensitive ( E*C_{50} = 0mu*g / m * l to 0.08mu*g / m * l ) , eight were moderately resistant (EC S0 = 0.19mu*g / m * l to 0.72mu*g / m * l ) and three were resistant ( E*C_{50} = 0.19mu*g / m * l to 0.72 ) to propiconazole. For difenoconazole, twenty-eight of these isolates were also found to be sensitive ( E*C_{50} = 0mu*g / m * l to 1.81mu*g / m * l ) to difenoconazole and the remaining two, resistant (E*C_{50} >= 24.29mu*g / m * l) . Target fungal isolates exhibited high resistance to the mixed commercial fungicide with E C S0 ranging from 60.87 µg/ml to 25,118.86 µg/ml which were found to be about 3,000 to a 1,000,000 times higher than the baseline E*C_{50} One non-target and eight target fungal isolates displayed resistance higher than reported E C s0 for other fungal isolates indicating the emergence of highly DMI-resistant strains within the fungal collection. This study highlights the importance of considering the sensitivity of epiphytic fungi to DMIs and their potential non-target effects. Understanding the specific responses of epiphytic fungi to difenoconazole and propiconazole can contribute to the development of more targeted and sustainable practices that minimize the negative impact on non-target organisms that have ecological roles in plant health and disease control.