USE OF ESSENTIAL OILS AND NANOPARTICLES FOR CONTROLLING PLANT PATHOGENS

Lettuce drop, a significant soilborne disease limiting lettuce production particularly under greenhouse conditions, is primarily caused by Sclerotinia spp. The aim of this thesis was to evaluate different sustainable strategies for the management of lettuce drop through the use potential of essential oils (EOs), biological control agents and chitosan-based formulations as alternatives to synthetic fungicides. In vitro experiments have shown that various EOs strongly inhibit S. sclerotiorum mycelial growth in a dose dependent manner. Thymus vulgaris EO provided complete inhibition but caused significant phytotoxicity, Rosmarinus officinalis, Lavandula hybrida, and Origanum majorana provided effective pathogen suppression with less phytotoxic effect. Greenhouse trials conducted two consecutive years confirmed that low concentrations of EO applications and chitosan significantly reduced disease severity. The treatment application of robotic precision spraying improved treatment selectivity eliminated phytotoxicity, reduced water consumption, and improved disease control. Under optimized conditions, sweet orange EO provided the highest effectiveness, reducing disease incidence by up to 74%, while Streptomyces spp. biological control agents ensured consistent moderate control. Analytical characterization highlighted the importance of formulation characteristics in biological performance. Quantitative 1H-NMR analysis has significant variability among commercial chitosan products in the degree of deacetylation, a key parameter affecting antifungal activity. The strong agreement between benchtop and high-field NMR systems validated the robustness and reproducibility of this analytical approach. A systematic review of nanoparticle-based plant protection strategies demonstrated their potential to enhance pathogen control and plant defense responses. The integration of EOs, chitosan, beneficial microorganisms, and nanotechnology give a promising avenue to reduce chemical inputs and promote environmentally sensitive plant protection.