Pepper wilt in southern Ethiopia

Fusarium wilt is one of the major biotic factors affecting hot pepper production in Ethiopia. Therefore, this study was designed with the objectives to assess the prevalence and incidence of hot pepper wilt in southern Ethiopia, determine the effect of biophysical factors on the intensity of the disease and evaluate the biocontrol potential of some antagonists for the management of the disease. For this purpose, field surveys were carried out in 80 fields across five major pepper growing districts of southern Ethiopia during the 2022 main cropping season. During the field surveys, data were collected on disease prevalence and incidence, and pathogen isolates were collected for characterization based on morphological features and pathogenicity test. The in vitro and in vivo efficacy of six Trichoderma spp. and Bacillus subtilis was investigated under dual culture assays and in a greenhouse, respectively. The disease was distributed across five hot pepper growing districts with 100% prevalence in the region. The highest (42.3%) and lowest (26%) mean incidence were recorded in Abeshege and in both Mareko and Wera districts, respectively. Soil analysis results revealed significant relationship between disease parameters on one hand and organic matter, soil moisture, total nitrogen and soil texture on the other. Soil pH had non-significant relationship with wilt incidence. Planting method and previous crop history were factors that significantly affected hot pepper Fusarium wilt incidence in the study areas in combination or solely. Twenty nine isolates of F. oxysporium were identified from the 80 samples based on macroscopic and microscopic characteristics. Isolate LWS7 was the most pathogenic and hence used in in vitro and in vivo bioassay. The highest (81.8%) and lowest (48%) mycelial growth inhibition were estimated from Trichoderma harzianum and Trichoderma hamatum, respectively. Lower wilt incidence (31%) was recorded on pepper plants following seedling root dip inoculation by Trichoderma viride. The present study confirmed the importance of hot pepper Fusarium wilt in southern Ethiopia, its association with biophysical factors, the variability of the isolates and efficacy of biocontrol agents tested. The efficacy and economic feasibility of hot pepper management through biocontrol agents may need additional investigation to come up with conclusive results.