Seasonal abundance and foliar damage of Spodoptera frugiperda (Lepidoptera: Noctuidae) on selected open pollinated maize varieties in Ibadan, Southwest Nigeria

The fall armyworm (FAW) is a highly destructive insect pest of maize that first invaded Africa in 2016 and has since posed additional constraints to maize production and food security in the region. Integrated Pest Management is a sustainable alternative to the sole use of insecticides for FAW control in Africa but its success relies on a good understanding of when the pest would occur. This study, therefore, investigated the seasonal abundance of FAW egg mass and larva on 25 open-pollinated maize varieties in the early and late planting seasons of 2018 and 2019 in Ibadan, southwest Nigeria. The relationship between larva abundance and foliar damage at three-, five- and seven weeks after planting was also investigated. Using standard procedures for maize varietal field trials and a 0 - 5 foliar damage rating scale, the study showed that FAW egg masses were relatively more abundant in the early seasons, especially at three weeks after planting (3WAP). Unlike egg masses, high larva abundance was observed in both seasons at 3WAP and 5 WAP but not at 7WAP. Varieties generally had moderate foliar damage scores in both seasons. Also, in both seasons, damage scores were strongly correlated with larva abundance at 3WAP and/or 5WAP but not at 7WAP. This suggests that observed foliar damage at 7WAP may not always be a true reflection of current larva infestation. In order to make timely and effective FAW management decisions, regular field scouting, especially within the first two weeks after planting, is recommended.