Apple Scab Disease Severity in the Sais Region of Morocco and its Sensitivity to Three Commercial Fungicides

  • Rachid LAHLALI Ecole Nationale d’Agriculture de Meknès, Department of Crop Protection, Phytopathology Unit, BP/S 40, Meknès 50001 https://orcid.org/0000-0002-1299-5733
  • Alieu MOININA Ecole Nationale d’Agriculture de Meknès, Department of Crop Protection, Phytopathology Unit, BP/S 40, Meknès 50001
  • Said EZRARI Ecole Nationale d’Agriculture de Meknès, Department of Crop Protection, Phytopathology Unit, BP/S 40, Meknès 50001
  • Dustin MACLEAN University of Guelph, Department of Plant Agriculture, N1G 2W1, Ontario
  • Mohammed BOULIF Ecole Nationale d’Agriculture de Meknès, Department of Crop Protection, Phytopathology Unit, BP/S 40, Meknès 50001
Keywords: apple cultivars; efficacy; Sais region; sensitivity; susceptibility; Venturia inaequalis

Abstract

Apple scab, Venturia inaequalis (Cooke) G. Winter, results in numerous fungicide applications in the Sais region of Morocco. We conducted the study to determine the susceptibility of cultivars through field survey and to evaluate the sensitivity of V. inaequalis to three fungicides using both in vitro and in vivo methods. We surveyed 100 apple orchards and collected two samples. Disease survey showed that the cultivars were highly susceptible to apple scab (grand mean of leaf scab: Golden Delicious, 40.31%; Starking Delicious, 20.45%; and Gala, 18.92%). Results underlined no significant differences between isolates in term of inhibition rate of mycelial growth and averaged disease severity. However, both treatment and concentration were statistically significant. EC50 values ranged from 2.33 µg/ml to 7.40 µg/ml and resistance factor (RF) values of 0.55, 1.02 and 1.79 were obtained for difenoconazole, trifloxystrobin and thiophanate-methyl, respectively. In vivo tests at a concentration of 10 µg/ml on the isolate ViIF using a curative method showed a high efficacy of trifloxystrobin (96.38%), and low efficacy of thiophanate-methyl (29.65%) and difenoconazole (24.62%). V. inaequalis was most sensitive to trifloxystrobin followed by difenoconazole and thiophanate-methyl, respectively. From this work, it was recommended testing more isolates and contact fungicides in order to develop a baseline sensitivity of the pathogen population against commonly used fungicides to treat the disease, as continued usage over time and the introduction of new fungal races may result in a decrease in fungicide efficacy.

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Published
2019-06-28
How to Cite
LAHLALI, R., MOININA, A., EZRARI, S., MACLEAN, D., & BOULIF, M. (2019). Apple Scab Disease Severity in the Sais Region of Morocco and its Sensitivity to Three Commercial Fungicides. Notulae Scientia Biologicae, 11(2), 249-257. https://doi.org/10.15835/nsb11210434
Section
Research articles