Adapting Microbial Inoculants, Plant Extracts, and Legume Intercrop to Mitigate Fall Armyworm (Spodoptera frugiperda) and Improve Maize (Zea mays L) Performance

Abstract

Infestation by the invasive fall armyworm-FAW (Spodoptera frugiperda) pest has recently emerged as an important constraint for maize (Zea mays L) production, which is frequently managed using chemical pesticides. However, the inappropriate use of chemical pesticides can cause deleterious effects on the environment and humans, and enhance pest resistance. This study evaluated the potential of locally produced microbial inoculants and plant bioactive extracts, and push-pull strategy of cowpea (Vigna unguiculata) intercropping as control measures for FAW infestation on maize plants, while serving as nutrient replenishing source via biological nitrogen fixation. This field study was setup as split plot in two alternate cropping seasons (September 2021 and April 2022) and cropping systems (mono- and inter-cropping) as main plots, and seven treatments as sub-plots (Control, chemical–NPK+Lamida gold, Tithonia diversifolia–Ti+Piper guineense–Pi, Plant growth-promoting bacteria–PGPB+Endophytic fungi–EF, EF+Pi and PGPB+EF+Ti+Pi). Results highlight statistical identical performance of microbial inoculants or plant bioactive extracts and chemical pesticides in reducing FAW infestation by 13-73.9 %. Bio-amendments significantly (P<0.05) increased maize height, 1000 maize grain weight, cob length and degree of filling compared to the untreated control. Maize-cowpea intercrop significantly increased FAW infestation in some treatments when compared to maize monocrop. In September 2021, FAW infestation correlated (P<0.05) negatively with 1000 maize grain weight (r = -0.7), cob length (r = -0.7), number of grains on the longest line (r = -0.8) and degree of filling (r = -0.7) in the monocrop plot. These findings highlight the ability of locally produced microbial inoculants and plant bioactive extracts as sustainable alternatives to mitigate FAW infestation on maize. Thereby, opening up possibilities for further investigation on mechanisms of action that can be explored for biological pest control.