Incidence and within field dispersion pattern of pod borer, Helicoverpa armigera (Lepidoptera: Noctuidae) in chickpea in Ethiopia

Abstract

Podborer is a major pest of chickpea in Ethiopia. Field surveys were conducted in 2013/2014 and 2014/2015 in central and northwestern Ethiopia to assess the prevalence and within field distribution of the pest. Although podborer was prevalent throughout the surveyed areas, there was a significant difference in larval density (0.10–3.75 larvae per m2) among zones and districts within zones. This variation was attributed to cropping history, cropping patterns, chickpea-crop adjacency, and weather (rainfall and temperature) conditions before and during the season as well as control measures applied. The optimum sample size required for precision ranged from 98, when podborer density was 10/m2, to 1045, when podborer density was ≤1/m2. Within field distribution of the larvae fitted a negative binomial distribution indicating that the larvae had a clumped/aggregated dispersion pattern. These results will enable chickpea stakeholders to develop and apply appropriate integrated crop management techniques for the control of podborer.