Precision management of Spodoptera frugiperda infestation hotspots in Bt and non-Bt corn crops with bioproduct applied and monitored via drone
Abstract Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a polyphagous pest widely distributed in tropical and subtropical regions, with reports of occurrence in various areas of the world. It encompasses 357 host plants, with emphasis on soybean (Glycine max L.), maize (Zea mays L.), and cotton (Gossypium hirsutum L.). The damage caused by this species severely compromises agricultural productivity and generates significant economic losses. Traditional management, based on intensive use of synthetic chemical insecticides, has had negative impacts on agroecosystems and on selected resistant populations. In this scenario, the use of drones and bioproducts emerges as a valuable tool for adequate sampling and sustainable management. Considering that NDVI versus NDRE comparison under real field conditions is still necessary, and the field-level validation of these spectral indices associated with bioproduct-based management in Bt and non-Bt corn remains limited, the present study aimed to detect, at the field level, the spectral reflectance of Bt and non-Bt corn plants infested with S. frugiperda larvae using the NDVI and NDRE vegetation indices derived from multispectral imaging acquired by remotely piloted aircraft (RPA). The experiment was conducted at the Chã de Jardim Experimental Area, UFPB, in Areia-PB, under a randomized block design (RBD). The varieties B2433PWU, Robusto, and Jabatão were evaluated. The treatments consisted of the application of Fitoneem® (active ingredients Azadirachtin A and B) and control (water) via DJI T40 spray drone. The results showed that leaf injuries can be efficiently monitored using remote sensing, with the NDVI index being the most effective. Infestation was influenced by both the cultivar and the applied treatment. In the Jabatão variety, applications of Azadirachtin reduced the expression of damage by up to 95%. Regarding production variables, only the number of grains per row and the number of grains per ear were significantly affected by the treatments. In practice, our research shows that the spectral reflectance of Bt and non-Bt corn plants infested with S. frugiperda larvae, as measured by the NDVI, is effective for validating the spectral response associated with bioproduct-based management in Bt and non-Bt corn fields.