Laboratory-to-field evaluation of ZnO nanoparticles for management of Fusarium solani–associated tea dieback

Tea dieback disease caused by Fusarium solani (Mart.) Sacc. is an emerging constraint to tea ( Camellia sinensis L.) production in several tea-growing regions, including Assam, India. In this region, the disease poses a growing threat to pluckable tea yield, with reported losses of up to 20% in harvestable shoots under severe infection, underscoring the need for more effective and judicious disease management strategies. In the present study, zinc oxide nanoparticles (ZnO-NPs) synthesized via a sol–gel route were evaluated for antifungal efficacy against F. solani under laboratory and field conditions, supported by comprehensive physicochemical characterization. X-ray diffraction confirmed the formation of phase-pure hexagonal wurtzite ZnO with an average crystallite size of 12.04 ± 2.45 nm. F. solani was isolated from infected tea plants in Assam, India, and identified by ITS region sequencing (GenBank accession PV171106.1) and TEF1-α sequencing (GenBank accession PX903872). In vitro assays demonstrated concentration-dependent inhibition of mycelial growth and spore germination, with ZnO-NPs showing stronger antifungal activity than zinc sulfate (ZnSO 4 ), which was used as a soluble ionic zinc control. The EC 50 for mycelial growth inhibition was 465.6 μg mL −1 for ZnO-NPs, compared with 992.4 μg mL −1 for ZnSO 4 , while spore germination was inhibited by up to 85.50 ± 2.22% at 1200 μg mL −1 . Scanning electron microscopy further revealed severe hyphal deformation and surface disruption following ZnO-NP exposure. Field evaluation demonstrated that short-term foliar application of ZnO-NPs significantly reduced disease severity, achieving up to 47.34% suppression by Day 30. Treated plants also exhibited lower disease intensity together with increased leaf chlorophyll content and enhanced foliar zinc accumulation. These findings confirm that ZnO-NPs possess measurable antifungal activity against F. solani under field conditions and may contribute to short-term suppression of tea dieback while simultaneously improving plant physiological status. However, because the field assessment was limited to a 30-day observation period, the results should be interpreted as evidence of short-term suppression rather than sustained long-term efficacy. Graphical abstract of ZnO-NPs synthesis, characterization and field application for control of Fusarium solani –induced tea dieback. • ZnO-NPs inhibited growth and spore germination of Fusarium solani more than ZnSO₄ at lower doses. • Short-term foliar application of ZnO-NPs reduced tea dieback severity under field conditions. • ZnO-NPs treatment increased leaf zinc content and chlorophyll levels in tea plants.