ANÁLISE DIGITAL DA HERBIVORIA DE Spodoptera frugiperda EM SOJA Bt VIA ÍNDICE ESPECTRAL VISÍVEL

Abstract

Soybean is one of the most important crops worldwide, with extensive use in human and animal nutrition, as well as applications in cosmetics, pharmaceuticals, and biofuels. In Brazil, soybean plays a crucial role in the economy, with the adoption of advanced agricultural technologies—such as genetically modified cultivars—being one of the main drivers of increased production. Bt soybean, which expresses insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt), provides protection against various pests, particularly those from the orders Coleoptera, Diptera, Hymenoptera, and Lepidoptera. However, the increasing resistance of pests such as Spodoptera frugiperda to the Cry1Ac protein found in some Bt cultivars compromises the effectiveness of this technology, making it necessary to develop complementary strategies to maintain efficient pest control. The objective of this study was to evaluate the application of digital imaging to quantify the efficacy of bioinsecticides in controlling Spodoptera frugiperda on Bt soybean by digitally analyzing the leaf area consumed by the caterpillar. The experiment was conducted between October and December in Uberlândia, Minas Gerais, using a transgenic soybean cultivar (RR and Bt technology). Six treatments were tested: chemical control (thiamethoxam and lambda-cyhalothrin), B. thuringiensis strains HD-1 and CCT 1306 (B1), B. thuringiensis var. aizawai strain GC 91 (B2), B. thuringiensis var. kurstaki strain HD-1 (B3), B. thuringiensis strains CCTB22, CCTB23, and CCTB25 (B4), and a control (no insecticides), with 20 replications per treatment. The leaves were treated and placed in trays, where they were exposed to larvae for assessment of foliar consumption. RGB images of the leaf blade were captured and used to determine the consumed area using R® software. The analysis revealed that the chemical control resulted in an average consumption of 2.6% of the soybean leaf area. The bioinsecticides showed variable efficacy, with treatments B2 and B3 displaying intermediate performance (approximately 52.2% of the soybean leaf area), whereas B1 and B4 were less effective (approximately 78.1% of the soybean leaf area). These results highlight the need to improve the formulation of bioinsecticides and to integrate different control strategies, such as the combined use of bioinsecticides and chemical insecticides, for more effective and sustainable integrated pest management.