Maize is one of the most important crops in southern Ethiopia. Africa maize stem borer, Busseola fusca is one of the important biotic constraints. Knowledge of its spatial distribution is important for improving sampling procedures and designing correct control strategies. The spatial distribution pattern of B. fusca was studied in southern Ethiopia during 2015 and 2016 cropping seasons. A total of 24 maize farms were visited in 12 kebeles. In each farm 2000 m2 area was measured and five sampling plots having 3 m × 3 m quadrats were taken in "X" fashion. In each spot percent of infested plants was calculated; the number of larvae and pupae were recorded. Sampling was carried out at mid-whorl, silking and maturity/harvesting stages of maize crop. Data were analyzed using distribution indices and Taylor’s power law. The distribution pattern of B. fusca varied between growth stages of maize crop. In addition, the degree of aggregation significantly varied between years and study areas. In both years, at silking as well as a mid-whorl stage of maize crop B. fusca larvae exhibited an aggregated distribution pattern in all study areas. However, B. fusca larvae at harvesting stage and pupae in both silking and harvesting stages of maize crop found randomly distributed. Percent of infested maize plants by B. fusca per field at the mid-whorl stage was taken and sampling size was determined. Percentage of infected plants and precision levels inversely related with the number of sample plants required in maize field.

Keywords: Busseola fusca, spatial distribution, sample size, precision level