Dose-Dependent Effect of Plant Volatiles on the Oviposition Preference of the Corn Leafhopper Dalbulus maidis

Abstract

Maize (Zea mays L.) is a major annual crop cultivated worldwide. In the Americas, the corn leafhopper Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) is a key pest of this crop, causing direct damage to plants through phloem feeding and indirect damage by transmitting phytopathogens. Despite extensive efforts, effective management and control of this pest remain challenging. In this study, we assessed the effects of volatile organic compounds (VOCs)—myrcene, linalool and methyl salicylate (MeSA), which are emitted by maize either constitutively or in response to herbivory plants—and methyl jasmonate (MeJA), a compound detectable in the volatile emissions of some maize genotypes. Dual-choice assays consisted of releasing female leafhoppers into cages containing a pair of maize plants: one associated with a dispenser loaded with the tested VOC at one of the three concentrations (2, 20 or 200 ng μ L⁻¹) and the other with a dispenser containing only the solvent (paraffin oil). Myrcene at 20 ng μ L⁻¹ significantly reduced oviposition, whereas MeSA at 2 ng μ L⁻¹, myrcene at 200 ng μ L⁻¹ and linalool at 200 ng μ L⁻¹ significantly increased the number of eggs laid on maize plants. MeJA, at any concentration, had no effect on oviposition preference of D. maidis. These results demonstrate a dose-dependent behavioural response of D. maidis to specific VOCs, with myrcene acting as a repellent at moderate dose and MeSA, myrcene (high dose) and linalool functioning as attractants. Such responses underscore the potential of these synthetic compounds for integration into semiochemical-based strategies aimed at manipulating D. maidis oviposition, either by deterring or attracting females, depending on the dose and compound used.