Tunisian isolates of Trichoderma spp. and Bacillus subtilis can control Botrytis fabae on faba bean

Faba bean crops worldwide are often attacked by different diseases, particularly chocolate spot caused by Botrytis fabae Sard. Fungal and bacterial isolates collected from faba bean and barley leaves in Tunisia were evaluated for their antagonistic potential against B. fabae. In a test on detached leaves, the highest rate of decrease in disease severity was scored by Trichoderma viride, followed by T. harzianum, the fungicide Carbendazim then Bacillus subtilis. Under glasshouse conditions, all tested fungi resulted in significant disease severity reduction. T. viride reduced the rate of chocolate spot infestation on leaves and stems by 35% and 31.5%, respectively, when the rate on the control was 100%. For T. harzianum, Carbendazim and B. Subtilis, the rates of infestation on the leaves were 41.7%, 43.1% and 59.7%, respectively. On the stems, T. harzianum scored the lowest rate of 54.2% followed by B. subtilis with 79.2% then Carbendazim with 87.5%. Two consecutive seasons of field trials using the Trichoderma species, B. subtilis and Carbendazim showed significant and consistent reduction in the severity of chocolate spot infestation rates. The highest protection against the disease was obtained from T. viride. Based on these results, Tunisian isolates of Trichoderma spp. can be recommended for developing commercial bio-fungicides for integrated management of chocolate spot.