Effects of cultivar resistances and chemical seed treatments on fusarium head blight and bread wheat yield-related parameters under field condition in southern Ethiopia.

Fusarium head blight (Fusarium graminearum Schwabe), FHB, is considered among the economically significant and destructive diseases of wheat. Thus, the study was worked out at seven sites in southern Ethiopia during the 2019 main cropping year to decide the effects of host resistance and chemical seed treatment on the progress of FHB epidemics and to decide grain yield benefit and yield losses derived from the use of wheat cultivars integrated with chemical seed treatments. The field study was worked out with the integration of two wheat cultivars, including Shorima as well as Hidase, and five chemical seed treatments, including Carboxin, Thiram + Carbofuran, Imidalm, Proceed Plus, and Thiram Granuflo. Twelve experimental treatments were arrayed in factorial arrangement with randomized complete block design. Each experimental treatment was replicated three times and delegated at random to experimental plots within a block. Significant (P < 0.01) variations were observed among the evaluated treatment combinations for rates of disease progress, incidence, severity, the area under the disease progress curve (AUDPC), and yield-related parameters across the locations. Results showed that the lowest incidence was registered on Shorima treated with Thiram + Carbofuran fungicide (27.40%). The lowest mean disease severity was recorded from Shorima integrated with Imidalm (21.23%) and Shorima treated with Thiram + Carbofuran (21.78%). The AUDPC was as low as 211.27, 226.39, and 236.46%-days were recorded on Shorima treated with Imidalm, Thiram + Carbofuran, and Proceed Plus, respectively. The highest disease severity of 57.91% (Hidase) and 27.22% (Shorima), and AUDPC of 552.71%-days (Hidase) and 313.04%-days (Shorima) were recorded from untreated control plots of the two cultivars. Paramount grain yield was found from Shorima treated with Imidalm and Dynamic fungicides, each of which was noted with GY of 4.40 and 4.05 t ha-1, respectively. Results also showed the highest yield losses (21.89 and 23.23%) were computed on untreated control plots of the cultivars Hidase and Shorima, respectively, compared with maximum protected experimental treatment for both cultivars. Moreover, cost-benefit analysis confirmed that Shorima treated with Imidalm exhibited the most prominent net benefit (NB) ($67,381.26 ha-1) and benefit-cost ratio (BCR) (4.43), followed by Shorima treated with Thiram + Carbofuran (NB of $60,837.76 ha-1 and BCR of 3.98). Based on the lowest yield loss and highest economic advantage, the use of Shorima treated with either Imidalm or Thiram + Carbofuran could be suggested to the farmers in the study areas and elsewhere having analogous agro-ecological conditions to manage the disease. However, sole use of chemical seed treatment is not as effective as post-anthesis aerial application up to maturity of the crop. For this reason, post-anthesis aerial application should be considered besides chemical seed treatment for effective management of FHB.

Integration of host resistance, fungicides, and spray frequencies for managing Fusarium head blight of bread wheat under field conditions in southern Ethiopia.

A field experiment was carried out in Adiyo, Bonke, Chencha, Sodo zuriya, and North Ari districts, they are found in Southern Ethiopia, during the 2019 main production season. The objective of the experiment was to evaluate the effectiveness of the integrations of host resistance and application of fungicides with designated spray frequency on Fusarium head blight under natural epiphytotic conditions and to determine the management effects on yield and yield components of wheat. The treatments consisted of wheat cultivars (Shorima and Hidase) and fungicides (Propiconazole and Tebuconazole) with four spray frequencies, including an unsprayed one. The experiment was arranged in a split-split plot design with three replications. Wheat cultivars were assigned to the main plots and fungicides allotted to the sub-plots, while the spray frequencies were appointed to sub-sub plots. Results exhibited that integration of wheat cultivars and fungicides with spray frequencies significantly (p < 0.001) reduced disease pressure and increased grain yields across the locations. The highest disease severity (36.46%) and area under disease progress curve (AUDPC) (404.78%-day) and lowest grain yield (2.42 t ha-1) were recorded at North Ari. The lowest severity (7.70%), and AUDPC (130.26%-day), and the highest grain yield (6.68 t ha-1) were recorded in Bonke. The lowest severity (4.78 and 5.74%) and AUDPC (52.86 and 59.78%-day) were recorded from Shorima due to integrated use of Tebuconazole with three and two times spray frequencies, respectively. The highest grain yield of 5.30 t ha-1 was recorded on Shorima in combination with Tebuconazole with three times spray frequencies. The grain yield loss of 46.49% was computed on unsprayed plots of Hidase cultivar. Overall, the results exhibited a combination of moderately resistance wheat cultivars supplemented by fungicide with appropriate spray frequencies right at disease onset reduced disease pressure and increased grain yield. Planting of Shorima combined with Tebuconazole with three times spray frequencies was found effective in reducing FHB epidemics and increasing grain yield with the highest monetary advantage. Therefore, this could be recommended to growers in the study areas and similar agro-ecologies to manage F. graminearum causing FHB in wheat.