Population dynamics of the fall armyworm, Spodoptera frugiperda J. E. Smith (Lepidoptera: noctuidae) on early and late season maize

Abstract

Maize (Zea mays L.), an important staple food crop in Nigeria is recently threatened by an invasive pest species; the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) in different parts of the country. Investigating the population dynamics of this pest will be useful for quantifying and forecasting future trends and provide a proper framework for control. A field experiment was conducted to investigate the dynamics of Spodoptera frugiperda on maize during the 2019 maize cropping season in Benin City, Edo State, Nigeria. Weekly data on number of larvae and number of plants with live larvae or fresh frass were collected on 20 maize plants randomly selected at five locations following a ‘W’ pattern in the bulk plot. Meteorological data were obtained from National Centre for Energy and Environment, University of Benin, Benin City. These data were analysed using Analysis of Variance (ANOVA), t-test and Pearson’s correlation analysis. Results revealed that in the early and late cropping season there was a significant difference (p<0.05) in the larval abundance, larval instar distribution and percentage infestation in the different sampling weeks (SW). Weather parameters varied in both seasons. Larval abundance had a significant negative correlation with rainfall and humidity and a significant positive correlation with temperature in the early season, however, in the late season; larval abundance had a non-significant correlation with rainfall and humidity but a significant negative correlation with temperature. FAW population and larval instar distribution were influence by the crop phenological stage and prevailing weather.