Progression of chocolate spot (Botrytis fabae) and grain yield of faba bean as influenced by integration of fungicide rate and host resistance in Southern Ethiopia

Chocolate spot is economically the most important and destructive disease of faba bean. Field studies were conducted to develop and determine an integrated option that consisted of host resistance and fungicide rates to reduce chocolate spot progression and minimize yield loss of faba bean at two locations in Southern Ethiopia in 2018 and 2019. The experiment was factorial arranged in a randomized block design with three replications. Results revealed cultivar, fungicide rate, and their interactions strongly (p < 0.001) influenced disease progress rate, severity, and area under disease progress curve (AUDPC). The lowest (0.0094–0.0254 units d­ay⁻¹) and the highest (0.0175–0.0393 units d­ay⁻¹) progression rates were computed from cultivar Gebelcho and local at all application rates, respectively. All cultivars highly reduced disease severity and AUDPC at 3 kg ­ha⁻¹ foliar application rate over controls at both locations and seasons. Cultivars and fungicide rates variably affected yield where Gebelcho (+63.09%), Moti (+55.58%), and Degaga (+54.91%) exceeded yield obtained from the local cultivar at Bonke in 2019. In addition, Degaga performed well at Chencha in both years. In addition, cultivars attained very low yield loss when treated at a rate of 2½ and 3 kg ­ha⁻¹ fungicide applications. Moreover, disease components established significantly negative relationships with yield parameters at both sites over years. Furthermore, integration of host resistance (Degaga and Gebelcho) and fungicide application rates of 2½ and 3 kg ­ha⁻¹ provided higher monetary advantages than the untreated plots. However, stability analysis, low yield loss and monitory advantage showed planting Degaga at a rate of 2½ kg ­ha⁻¹ was the most cost-effective option in reducing disease pressure and increasing yield parameters; and suggested to growers in the study areas.