Obligate endosymbionts as promising targets for planthopper pest control: Exploring their effect on probing behavior

BACKGROUND: Planthoppers (Hemiptera: Delphacidae) are sap-sucking insects that have emerged as major pests of economically important agricultural crops worldwide. These insects establish an obligate mutualistic relationship with fungal endosymbionts (yeast-like symbionts, YLS) which play a key role in their nutrition and physiology. Despite this, the influence of YLS on host probing behavior remains poorly understood. In this study, we experimentally reduced YLS abundance in the maize planthopper Delphacodes kuscheli, the main vector of Mal de Río Cuarto virus in the Neotropical region, by exposing host plants to systemic fungicides. We then evaluated the effects of YLS depletion on female probing behavior using the electrical penetration graph technique. RESULTS: Sub-symbiotic females showed longer non-probing periods (mean values, 95% CI 70.80 min, 46.3-108) than control females (19.59 min, 12.8-30). They also required more probes and more time to reach the phloem and allocated less time to phloem sap ingestion (113.82 min, 84.9-153) than control females (180.96 min, 136.4-240). Additionally, sub-symbiotic females exhibited a higher proportion of probing time spent in pathway activities (32.52%, 26.30-39.42) than control females (22.38%, 17.13-28.70). CONCLUSION: These findings suggest that nutritional symbionts may play an overlooked role in shaping probing behavior in D. kuscheli females. Our results highlight the ecological significance of YLS in these phloem-feeding insects and provide novel insights into symbiont-vector-plant interactions. The ability to alter probing behavior through reduction of obligate mutualistic symbionts in an agricultural pest opens new avenues for the development of integrated pest management strategies. © 2026 Society of Chemical Industry.