Effect of integrating variety, seed treatment, and foliar fungicide spray timing on managing common bean Anthracnose at Bako, western Ethiopia

Abstract

Bean anthracnose [Colletotrichum lindemuthianum (Sacc. And Magn.) Lams.-Scrib] is one of the major diseases of common bean (Phaseolus vulgaris L.), and causes huge yield losses in western Ethiopia. The research was conducted at Bako during 2014 main cropping season with the objectives to: 1) assess the efficacy of seed treatment and foliar fungicide spray timing; 2) determine the effect of integrated use of common bean varieties, seed treatment and foliar fungicide spray timing on anthracnose severity, yield and yield components; and 3) assess the economic feasibility of the treatments. The treatments consisted of three bean varieties (Awash Melka, Awash-1 and Mexican 142), two levels of seed treatment (thiram-treated at the rate of 5 g kg^-1 seed and non-treated) and four foliar spray timing with tebuconazole at the rate of 350 ml ha^-1 (at the fifth trifoliate, flowering, pod setting stages and unsprayed control). The experiment was laid out as a randomized complete block design (RCBD) in a factorial arrangement and replicated three times per treatment. Disease parameters were assessed from 18 pre-tagged plants per plot; yield components were assessed from ten randomly pre-tagged plants; seed yields were recorded from plants in the three central rows in each plot. Variety, seed treatment, and foliar spray timing interacted significantly (p  ≤ 0.05) to influence foliage and pod disease severity index, area under the disease progress curve (AUDPC), infected pod per plant and seed yield. Awash-1, without seed treatment and without foliar spray, showed the highest (86.0%) foliage severity and the highest (71.32%) pod severity with calculated AUDPC values of 2771.19 and 1150.25%-days for leaf and pod, respectively. Mexican 142 from treated-seed and sprayed with tebuconazole at the fifth trifoliate stage produced the highest (2354.074 kg ha^-1) seed yield, followed by Awash-1 (2239.76 kg ha^-1) from non-treated seed and sprayed starting at the flowering stage. The highest marginal rates of return of 3071 and 2568% were calculated for Awash-1 without seed treatments but sprayed at flowering and pod setting, respectively, followed by Awash Melka (1962%) that was sown without seed treatment but sprayed at the flowering stage. Therefore, Awash-1 and Awash Melka without seed treatment and spraying with tebuconazole at the flowering stage resulted in the optimum yields of the crop, indicating that these treatments could be practiced as the most effective management measures against common bean anthracnose for sustainable production of the crop in the study area and elsewhere with similar agroecologies.

Keywords: Area under the disease-progress curve (AUDPC); [Colletotrichum lindemuthianum (Sacc. and Magnus) Lams.-Scrib]; Phaseolus vulgaris L.; foliar spray timing seed treatment