Bioestimulantes e voláteis de plantas como ferramentas para o manejo de dalbulus maidis (DeLong & Wolcott) (hemiptera: cicadellidae) em milho

Abstract

The growing agricultural demand has intensified the use of phytosanitary products, whose excessive and improper application has caused significant impacts on ecosystems. In this context, it becomes essential to develop more sustainable production systems, especially in crops such as maize (Zea mays L.), which is heavily affected by the corn leafhopper, Dalbulus maidis (DeLong & Wolcott, 1923) (Hemiptera: Cicadellidae), one of the main pests of this crop. Given this scenario, the present dissertation aimed to investigate the application and effectiveness of different bioinputs as management strategies for D. maidis. In this study, we evaluated the effects of silicon (Si) and humic substances (HS), applied individually or in combination, on plant growth, colonization, and establishment of D. maidis through behavioral and biological analyses, as well as the assessment of plant defense mechanisms under controlled conditions. The biostimulants did not influence shoot growth, although HS alone promoted root development—an effect that was suppressed when combined with Si. Treatments with Si and Si+HS reduced host plant acceptance for oviposition, without negatively affecting the insect’s biological parameters. Notably, the Si+HS treatment accelerated the development of the first nymphal instar of the leafhopper on maize plants. Although Si treatment slightly enhanced maize resistance to the pest, this effect was not associated with increased levels of total phenolic compounds. Si, whether applied alone or in combination with HS, exhibited a protective effect against pest-induced oxidative stress by reducing the activities of superoxide dismutase (SOD) and catalase (CAT). We also evaluated the effects of the volatile organic compounds (VOCs) myrcene, linalool, methyl salicylate (MeSA), and methyl jasmonate (MeJA) on oviposition preference of D. maidis. In choice bioassays, myrcene at 20 ng μL⁻¹ significantly reduced oviposition, while MeSA at 2 ng μL⁻¹, myrcene at 200 ng μL⁻¹, and linalool at 200 ng μL⁻¹ increased the number of eggs laid. MeJA, however, did not influence oviposition behavior at any of the tested concentrations. These results demonstrate dose-dependent behavioral responses of the pest to specific VOCs, with myrcene acting as a repellent at moderate doses, while MeSA, high-dose myrcene, and linalool acted as attractants to D. maidis. Altogether, the findings highlight the potential of biostimulants and VOCs as promising tools for the integrated management of the corn leafhopper, offering sustainable alternatives capable of modulating the oviposition behavior of D. maidis. Key words: Silicon; Humic Substances; semiochemicals; corn leafhopper; plant defenses; olfactory responses.