Field Responses of Provitamin A Fortified Maize (Zea mays L.) Varieties to Fall Armyworm (Spodoptera frugiperda J. E. Smith) Infestation and Natural Enemies

Abstract

The fall armyworm (FAW), has successfully invaded Africa, posing a significant threat to maize production across the continent. In this study, two pro-vitamin A varieties, SYN 2 and SYN 13 were evaluated for their performance under fertilised and unfertilised soils against FAW infestation and damage, while monitoring the presence of native parasitoids and predators at the Institute of Agricultural Research and Training in Ibadan. The field plot was laid out in a split-plot design with three replications. The main plot was treated with or without nitrogen fertiliser (75 kg/ha), while the two varieties were placed in the subplots. Twenty plants per plot were sampled to assess the percentage infestation and relative density of larvae. Damage was rated fortnightly using a scale of 1 to 9, and grain yield was determined at harvest. Indigenous parasitoids and predators were assessed from field-collected larvae following standard procedures. The relative abundance and parasitism rate of parasitoids were determined. The percentage infestation varied considerably, from 17% (unfertilised SYN 13) to 100% (fertilised SYN 2 and SYN 13). The relative density of FAW larvae ranged from 0.17±0.17 in unfertilised to 2.32±0.61 in fertilized plots. Foliar damage ratings ranged from 1.3 on unfertilised SYN 13 to 7.0 on fertilized SYN 13. The highest grain yield, 2.3 t/ha, was obtained from fertilised SYN 13. Two larval parasitoids, Coccygidium luteum and Chelonus sp., were recorded, with C. luteum showing a parasitism rate and relative abundance of 32.5% and 92.86%, respectively. Insect predators recorded includes; Crematogaster sp., Cheilomenes lunata lunata, Forficula auricularia and Zelus sp. Fertilised SYN 2 and SYN 13 suffered higher larval infestation and damage but yielded better crops. Parasitoids represent a promising means of control against FAW, although further studies are required to assess their potential in field conditions.