TY - JOUR AU - LAHLALI, Rachid AU - MOININA, Alieu AU - EZRARI, Said AU - MACLEAN, Dustin AU - BOULIF, Mohammed PY - 2019/06/28 Y2 - 2024/03/29 TI - Apple Scab Disease Severity in the Sais Region of Morocco and its Sensitivity to Three Commercial Fungicides JF - Notulae Scientia Biologicae JA - Not Sci Biol VL - 11 IS - 2 SE - Research articles DO - 10.15835/nsb11210434 UR - https://notulaebiologicae.ro/index.php/nsb/article/view/10434 SP - 249-257 AB - <p style="text-align: justify;">Apple scab, <em>Venturia inaequalis</em> (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 <em>V. inaequalis</em> to three fungicides using both <em>in vitro</em> and <em>in vivo</em> 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. EC<sub>50</sub>&nbsp;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. <em>In vivo</em> 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%). <em>V. inaequalis</em> 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.</p> ER -