Parasitoids Associated with the Invasive Fall Armyworm, Spodoptera Frugiperda (J.E. Smith) Under Biorational Insecticide Treatments

Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith) is presently the most economically important pest of maize in sub-Saharan Africa. Synthetic insecticides have been the most reliable control option since its invasion in the sub-region. The outbreak of the pest in Africa has led to several recommendations of insecticides, including biopesticides. However, the effects of these products on the environment, especially on parasitoid species have not been assessed under field conditions. Studies were conducted in Nyankpala and Nanton-Changnayilli in the northern region of Ghana during the 2024 cropping season to determine the influence of selected biorational insecticides on parasitoid species associated with the pest. The biorational insecticides; Grow-Safe (3% Azadirachtin), Eradicaot (282 g/l Maltodextrin), Agoo (Bt 55% + Monosultap 45%), Bypel 1 (Perisrapae granulosis virus + Bacillus thuringensis 5%) and the synthetic insecticide, Ema Star (Emamectin benzoate 48 g/l plus acetamiprid 64 g/l) were applied on 11 selected farms. Samples of S. frugiperda larvae were collected from the fields and incubated to determine the parasitoid species emerged, their relative abundance and parasitism rates. Three parasitoid species of the pest were identified. These were Coccygidium luteum (Brulle), Chelonus bifoveolatus (Szepligeti) and Charops sp. C. luteum was the most abundant parasitoid and with the highest parasitism rate whilst Charops sp was the least abundant in the surveyed areas. Parasitoid abundance and parasitism rates increased with botanical insecticide application over the synthetic insecticide. The botanical insecticide Grow-safe (Azadirachthin) recorded the highest parasitoid abundance and parasitism rate. Ema star recorded the least parasitism rate and parasitoid abundance. Management of FAW in the savanna zone should focus on the use of Grow-safe in order to conserve the population of C. luteum for biocontrol interventions.