Silício em algodoeiro como indutor de resistência aos lepidópteros-praga Alabama argillacea e Spodoptera frugiperda

Abstract

Cotton is a crop of great economic importance for the textile industry and for income generation in Brazilian agribusiness. However, its cultivation faces serious challenges due to attacks by insects, especially caterpillars such as Alabama argillacea and Spodoptera frugiperda. These insects cause intense defoliation and damage to reproductive structures, compromising productivity and fiber quality. Managing these pests requires integrated strategies, such as biological and chemical control, and cultural practices. The adoption of sustainable technologies is essential to reduce losses and preserve crop competitiveness. This study aimed to assess the development, survival, and reproduction of A. argillacea and S. frugiperda on cotton leaves treated with varying doses of silicon (Si). Two experiments were conducted: the first evaluated the effects of silicon on the biological parameters of A. argillacea, while the second focused on S. frugiperda. Both experiments were carried out under greenhouse conditions and in the Entomology Laboratory of Embrapa Cotton, located in Campina Grande, Paraíba state, Brazil. The experimental design was a randomized complete block design with three treatments, distributed into five replicates. Treatments consisted of A. argillacea or S. frugiperda caterpillars feeding on cotton leaves collected from plants without Si (T1) or fertilized with 150 mg kg-1 (300 kg Si ha-1) (T2) and 300 mg kg-1 (600 kg Si ha-1) (T3) of Si applied to the soil. Cotton plants fertilized with Si at doses of 150 and 300 mg kg-1 of soil accumulated this nutrient proportionally in their leaves, reducing the development, survival, and reproduction of A. argillacea. Spodoptera frugiperda caterpillars fed on silicon supplemented cotton leaves had a shortened larval period, with an irregular and disordered growth pattern. Female S. frugiperda moths hatched from caterpillars fed on silicon supplemented cotton plants had limited oviposition period, longevity, number of eggs, and predicted egg and egg mass per female. Multivariate analysis of S. frugiperda's reproductive parameters revealed two groups: one composed solely of the control and the other of treatments with 150 and 300 mg kg-1 of silicon. The difference between the 150 and 300 mg kg-1 doses was reduced compared to the control. This result suggests that these doses influenced several reproductive variables of S. frugiperda. These findings confirm that soil-based silicon application somehow interferes with specific stages of the caterpillars' life cycle, compromising their development. This indicates that silicon use may be a promising strategy for managing these lepidopteran pests.