Comparative Toxicity of Limonoid-Based Commercial Botanical Insecticides in the Management of Corn Leafhopper—The Corn Stunt Complex Vector
摘要
In the search for alternative tools for the management of Dalbulus maidis, the corn stunt disease vector, the use of multi-target formulations based on neem derivatives remains unclear, despite their widespread use in Brazil and elsewhere. In this study, we employed high-performance liquid chromatography coupled with mass spectrometry (HPLC/MS) to quantify the concentrations of the primary active ingredients in these formulations. Additionally, we evaluated the lethal toxicity and feeding and oviposition deterrence of these formulations. The chemical analysis revealed a distinctive chemical profile and variable levels of the major bioactive components of these formulations (azadirachtin and 3‑tigloylazadirachtol), but with levels of these compounds below those attested in the product leaflet. In topical application bioassays, Fitoneem® (LC50 = 1251 mg L−1) and Lagartol® (LC50 = 1316 mg L−1) were observed to cause mortality in more than 80% of D. maidis adults, exhibiting equitoxicity to the positive control (ethripole). In contrast, Original Neem® and Original Plus® showed greater lethal toxicity for D. maidis adults through residual contact, however, at a lower level of activity. Additionally, Openeem Valente® demonstrated potential in deterring D. maidis oviposition. Moreover, all formulations tested demonstrated the ability to reduce the feeding of D. maidis nymphs and adults, with the exception of Bioexos Plus®, which did not exhibit any significant deterrent effect on adult insects. Thus, the levels of lethal and sublethal toxicities observed in these limonoid-based formulations can contribute to D. maidis management and, consequently, reduced the impact of corn stunt complex diseases in cornfields.