Trichoderma harzianum and some antioxidants for suppressing faba bean chocolate spot incidence under natural field infection

Abstract

Chocolate spot is one of the most important diseases affecting faba bean in Egypt. The field experiment was conducted for two cropping seasons with the objective of evaluating the efficacy of 'Trichoderma harzianum' and five antioxidant agents, i.e. Vitamin C, Vitamin E, Selenium, VitaMax Plus against Chocolate spot disease incidence and severity under field conditions. Field study was performed during two successive growing seasons (2015/2016 and 2016/2017) using the bioagent T. harzianum and antioxidants individually or in combinations. All treatments were applied as faba bean foliar spray three times with 15 days interval starting at the beginning of flowering stage. Percentages of disease incidence and severity were measured for each growing season and their mean was calculated. Results showed that all applied treatments could reduce chocolate spot disease incidence at a range of 66.6 to 92.2% compared to the fungicide Diathane M45 (39.0%). Meanwhile, disease severity followed similar trend. It was reduced by a range of 38.7 up to 75.1% and 20.9% relatively to control at applied treatments of antioxidants individually or combined with 'T. harzianum' and the fungicide, respectively. Combined treatments showed that when 'T. harzianum' combined with either one or all of the used antioxidants, they had superior effect for reducing disease incidence and severity on faba bean plants compared to fungicide and the control. Meanwhile, all of the antioxidants in combination showed lesser suppression effect on disease incidence and severity than individual treatment. The present findings demonstrate that bio-agent 'T. harzianum' integrated with antioxidant as foliar spray treatment can be recommended for the future use in a commercial scale for effective management of Chocolate spot on faba bean.