Association of Root Rot Disease With Common Bean Stem Maggot ( <i>Ophyiomia phaseoli</i> ) and Testing of Insecticides for Stem Maggot Control on Common Bean ( <i>Phaseolus vulgaris</i> L.) in West Hararghe, Ethiopia

Bean stem maggot (BSM) and root rot are significant pests of common beans in terms of economic impact. The wounds caused by the feeding of BSM act as entry points to root rot‐causing pathogens. The objective of this paper is to assess root rot disease associated with stem maggots and evaluate insecticides for managing stem maggots on common beans in west Hararghe, Ethiopia. This study contained two parts survey and field experiment. The survey part was conducted at different common bean growing agro‐ecologies of the west Hararghe zone namely Oda Bultum, Habro, and Chiro districts, while the field experiment was conducted at Habro district, Bareda, Oda Bultum University farm site. Twenty farms were chosen at random from four kebeles in each district to study the occurrence and impact of bean root rot and BSM separately, as well as their interactions. All bean roots were inspected for the existence of BSMs and pathogens responsible for root rot disease. The findings indicated that there were notable occurrences of bean root rot diseases and BSMs in the areas that were examined, with statistically significant results ( p &lt; 0.05). Rhizoctonia solani , Pythium spp., and Fusarium spp. were the major root rot pathogens isolated. Ophyiomia phaseoli was the dominant BSM in surveyed districts. The incidence of common bean fly and root rot computed was a significant difference ( p &lt; 0.05) among surveyed districts. The highest disease and bean fly interaction incidence (50.85%) was obtained from the chiro district followed by Habro (36.04%). The least disease and bean fly interaction incidence (26.97%) was recorded from the Oda Bultum district. Six insecticides, namely Confidor SL 200, Karate 5% EC, Dimeto 40% EC, Alpha guard, Apron Star 42 WS, and Bravo 5% EC (W/V), were tested in a field experiment against an unsprayed control to assess their differences. Common bean agronomic parameters showed significant variations ( p &lt; 0.0001–0.05) among the treatments compared to the control. Grain yield ranged from 1095 to 2950 kg/ha observed among treatments. Confidor SL 200 followed by Apron Star 42 WS and dimethoate 40% significantly reduced the number of BSMs and increased common bean agronomic yield and yield component parameters.