Fungicidal management of chocolate spot of faba bean and assessment of yield losses due to the disease

Abstract

This work was carried out at Sers El-Lyain Agriculture Research Station Farm, El-Minufiya Governorate during 2007/08 and 2008/09 growing seasons to evaluate the amount of losses in the seed yield of the five faba bean cultivars Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2 under. In vitro studies show that Dithan M45 was the most effective agent against Botrytis fabae than Galben manozeb and copper oxychloride. Application Dithan M45 of under greenhouse conditions, 2 days before inoculation reduced the disease severity (3.11%) at 200ppm compared with the control treatment (18.59%) on Giza 40 cv., while the symptoms did not appear at the same concentration on other tested cultivars. It was observed that, the cvs. Giza 716 and Sakha 2 showed lower infection than the other tested cvs, except with Giza 40 which was highly susceptible. Field studies showed significant differences under the influence of chocolate spot disease. The area under the disease progress curve (AUDPC) was higher on Giza 40 followed by Sakha 1, Giza 3 Mohassen, Sakha 2 and Giza 716, respectively, with higher disease infection in the first season 2007/08 than 2008/09 season. High negative significant correlation (r) was obtained between AUDPC and the yield of the five tested cultivars in the two seasons. High negative correlation was observed between disease severity and each of plant height, number of branches, number of pods, weight of pods and weight of 100 seeds of Giza 40 and Sakha 1 in the first season. High negative regression coefficient (b) was found between each of the five studied characters and disease severity of five cultivars. However, plant height and number of branches were not significant for the Giza 716 and Sakha 2. The regression coefficient (b) values were found significant for number of pods (X3) with 0.532 and 0.096, for weight of pods (X4) with 0.422 and 0.0126 and for weight of 100 seed (X5) with 0.753 and 0093 for Giza 716 in the two seasons, respectively. While for Giza 40 these values were 0.644 and 0.226, 0.115 and 0.64 and 0.159 and 0.222, respectively. Coefficient of determination (R2) values were 0.63 and 0.341 for Giza 716 and were 0.757 and 0.854 for Giza 40 for the weight of pods in the two seasons, respectively.