Modelling the biocontrol of Spodoptera frugiperda: A mechanistic approach considering Bt crops and oviposition behaviour

Abstract

The fall armyworm (Spodoptera frugiperda Smith & Abbot, 1797, Lepidoptera, Noctuidae) is a widespread agricultural pest native of the Americas. It is a lepidopteran pest with the ability to consume an enormous variety of crops. There are several control strategies, including natural enemies employed to control the pest, particularly egg parasitoids and genetically modified crops with Bacillus thuringiensis Berliner, 1915, Bacillaceae (Bt) toxins. However, the constant use of Bt crops has allowed the emergence of positive selection pressure to create pests increasingly resistant to the toxins. Furthermore, female moths can lay eggs in layers and deposit scales to enhance their defences against egg parasitoids. In the present work, we intend to understand how (i) the attack rate of the parasitoid, (ii) the degree of vulnerability of the eggs to parasitism, and (iii) the mortality caused by Bt toxins affect crop production and the overall dynamics. We developed a tritrophic crop-pest-parasitoid mathematical model to study the fall armyworm dynamics focusing on crop density. Our findings indicate that crop production decreases by approximately 60.03% in the absence of parasitoids. We discuss the results regarding pest resistance to Bt toxins, pest defence against parasitism, and the selection of parasitoids for pest control, and propose potential extensions for future work.