Evaluating the efficacy of fungicides for the management of Sorghum (Sorghum bicolor) anthracnose (Colletotrichum spp.) in West Gondar.

Abstract

Sorghum is a critical food crop in Ethiopia, yet its productivity is severely threatened by anthracnose, caused by Colletotrichum sublineolum. The present study was conducted in West Gondar, Amhara Region, during the 2022 growing season, with field experiments established at Metema and West Armachiho. A randomized complete block design with three replications was employed to evaluate the efficacy and profitability of various fungicide regimes. Treatments included both single and combined applications of Thiram, Tilt, Redomil, and Natura, delivered as seed dressings, foliar sprays, or their combination, alongside an untreated control. The experiments utilized the susceptible local cultivar 'Tewzale' in 4 × 3 m plots, with 5 cm intra-row and 75 cm inter-row spacing. Statistical analysis indicated highly significant differences among treatments for key parameters: percent severity index (PSI), area under the disease progress curve (AUDPC), yield, and thousand seed weight (TSW) (p < 0.0001). Both location and treatment × location interactions were significant, especially for PSI at 65, 75, and 86 days after planting. The most effective disease suppression and lowest AUDPC values were observed with Tilt plus Thiram and Natura plus Thiram treatments, while untreated controls experienced the highest disease pressure. Notably, the Natura plus Thiram combination resulted in the highest grain yield (4614.6 kg ha⁻¹) and TSW (17.7 g), with the untreated control producing the lowest values (2076.6 kg ha⁻¹). Relative yield loss was completely mitigated by Natura plus Thiram, whereas the control plots recorded up to 61.8% loss. Economic assessment through partial budget analysis revealed that Natura plus Thiram was the most profitable option, delivering a net benefit of 79,162 ETB and a marginal rate of return of 2881.33%. Natura alone and Redomil plus Thiram also generated substantial returns, but to a lesser extent. In conclusion, integrating seed dressing with foliar fungicide applications specifically the Natura plus Thiram combination proved to be both an effective and economically viable strategy for managing sorghum anthracnose. For optimal results, this approach should be complemented by the use of resistant varieties and adherence to sound agronomic practices.