Insect pests like thrips attack onion crops and cause a yield loss of 30%—90% in the Mecha district. Hence, field research was conducted in Mecha District, Ethiopia, under irrigation conditions in 2019/2020 to develop management options for onion thrips. The treatment combinations were: two onion varieties: Adama red and Bombay red; two botanicals, namely, Datura stramonium and Azadirachta indica leaf powder, and the two synthetic insecticides, dimethoate (40%) and karate (5%). The study was set up in a randomized full-block design and repeated three times. Data were recorded and an analysis of variance was performed 3 times. The highest mortality percentage (65%) with the lowest population of thrips per plant (1.66) was shown from the Adama red variety treated with Datura stramonium. The lowest mortality (24.43%) with a high population of thrips per plant (4.0) was shown on Bombay red treated with Karate 5% EC. Bombay treated with Karate 5% EC gave the highest mortality percentage (53.3%), plant height (13.2 cm), marketable yield in kg ha-1 (8600, and total yield ha-1 (9441), subsequently Adama red treated with Datura stramonium. Partial budget analysis revealed that the application of Karate 5% EC ha-1 on the Bombay red variety yielded the highest net benefit with the lowest production cost that can be recommended for the study area.