Chocolate spot caused by Botrytis fabae is one of the major biotic constraints of faba bean production in the highlands of Ethiopia. Therefore, the current work was designed to evaluate the effect of varieties and fungicide spray frequency on disease development and crop performance. Field experiments involving four faba bean varieties and four fungicide (Mancozeb 80% WP) spray frequencies were carried out at two locations i.e. Atsela and Ayba. The experiments were arranged in 4 x 4 factorial combinations in a randomized complete block design. Data were collected on disease incidence and severity as well as faba bean yield and yield components. Results suggested significant (P < 0.05) effects of varieties and fungicide frequencies on disease intensity, agronomic traits, yield and yield components of faba bean. However, variety-fungicide frequency interaction effects were not significant. The disease occurred at 46 and 52 days after planting at Atsela and Ayba, respectively. Disease severity was the highest on the local variety and the lowest on variety Walki regardless of the location. Besides, chocolate spot was the most severe on unsprayed plots both at Atsela and Ayba. On the other hand, three times Mancozeb 80% WP application resulted in the lowest AUDPC i.e. 1023%-days at Atsela and 1107%-days at Ayba. The disease resulted in grain yield loss of up to 34.9, 26.9 and 15.28% on unsprayed, once sprayed and twice sprayed plots, respectively. The highest cost benefit ratio (1:10.8) was obtained from three times fungicide application followed by two times (1:8.93) and once (1:7.08) application frequencies. The present findings ascertain the importance of chocolate spot in the region. Walki variety and three times Mancozeb 80% WP application appeared to be the best option for the management of chocolate spot in the region. However, current results need to be verified in multi-location and multi-season trials to come up with conclusive recommendation.
Keywords: Cost-benefit ratio, Incidence, Severity, Fungicide frequency, Yield loss