Assessing Venturia inaequalis Response to Common Fungicides in Morocco

Area of Science:

• Plant Pathology
• Agricultural Entomology
• Fungal Genetics

Background:

• Apple scab, caused by Venturia inaequalis, is a significant threat to Moroccan apple production.
• Over-reliance on fungicides has led to increasing reports of Venturia inaequalis resistance.
• This resistance compromises the efficacy of disease management and orchard economic sustainability.

Purpose of the Study:

• To evaluate the sensitivity of Moroccan Venturia inaequalis isolates to key fungicides.
• To assess the efficacy of difenoconazole, trifloxystrobin, and thiophanate-methyl against apple scab.
• To inform sustainable apple scab management strategies in Morocco.

Main Methods:

• Isolation and identification of five Venturia inaequalis strains from the Fes-Meknes region.
• Morphological and molecular (ITS region) confirmation of isolate identity.
• In vitro and in vivo assays to determine fungicide sensitivity (EC50 values) and efficacy.

Main Results:

• Difenoconazole showed high efficacy (EC50: 0.05–1.46 µg/mL), reducing disease severity by up to 85.8%.
• Trifloxystrobin and thiophanate-methyl exhibited high EC50 values (2.94–29.62 µg/mL and 14.84–1237.20 µg/mL, respectively), indicating widespread resistance.
• Preventive fungicide applications were significantly more effective than curative treatments for all tested fungicides.

Conclusions:

• Urgent revision of apple scab management strategies in Morocco is required.
• Fungicide rotation and integration of non-chemical methods are crucial for sustainable control.
• Continuous sensitivity monitoring and molecular diagnostics are recommended for effective disease management.