Bacterial speck disease, caused by Pseudomonas syringae pv. tomato (Pst), is one of the most pervasive biological adversities in tomato cultivation, in both industrial and in table varieties. In this work synthesis, biochemical and antibacterial properties of a novel organic nanostructured pesticide composed of chitosan hydrochloride (CH) as active ingredient, cellulose nanocrystals (CNC) as nanocarriers and starch as excipient were evaluated. In order to study the possibility of delivering CH, the effects of two different types of starches, extracted from a high amylose bread wheat (high amylose starch—HA Starch) and from a control genotype (standard starch—St Starch), were investigated. Nanostructured microparticles (NMP) were obtained through the spray-drying technique, revealing a CH loading capacity proximal to 50%, with a CH release of 30% for CH-CNC-St Starch NMP and 50% for CH-CNC-HA Starch NMP after 24 h. Both NMP were able to inhibit bacterial growth in vitro when used at 1% w/v. Moreover, no negative effects on vegetative growth were recorded when NMP were foliar applied on tomato plants. Proposed nanostructured pesticides showed the capability of diminishing Pst epiphytical survival during time, decreasing disease incidence and severity (from 45% to 49%), with results comparable to one of the most used cupric salt (hydroxide), pointing out the potential use of CH-CNC-Starch NMP as a sustainable and innovative ally in Pst control strategies.

Nanomaterials in agriculture represent one of the most innovative method for protecting crops, due to possibility of being applied as nanopesticides or nanocarriers for active ingredients. Furthermore, nanotechnology could be combined with the concept of circular economy through the opportunity of obtaining highly technological nanometric materials starting from agro-industrial wastes. The present research evaluated the possibility of synthesizing cellulose nanocrystals (CNCs) from olive pruning wastes through chemical bleaching, reusing them as sustainable tool to control the causal agent of the olive knot disease (Pseudomonas savastanoi pv. savastanoi). CNCs showed an interesting in vitro effect in inhibiting bacterial growth and bacterial biofilm formation, as well as the ability of reducing bacterial epiphytic survival in a comparable way to copper sulphate on leaf surfaces, when used at 1% w/v. CNCs were at the same time investigated for their interaction with olive tree seedlings, showing no negative effects on leaf development, and a promising root uptake, indicating that CNCs could be used also as nanocarriers for active ingredients. Obtained results highlight the innovative possibility of designing sustainable plant protection strategies capable of revalorise lignocellulosic wastes, meaning a simultaneous low environmental impact thanks to reduction of traditional agrochemicals input.

Quarantine pathogens require the investigation of new tools for effective plant protection. In particular, research on sustainable agrochemicals is the actual challenge. Plant extracts, essential oils, and gels are natural sources of efficient biocides, such as aromatic secondary metabolites. Thymol is the major phenolic constituent of thyme and oregano essential oils, and it can inhibit many pathogenic microbes. Thymol nanoparticles were obtained through adsorption on CaCO₃ nanocrystals, exploiting their carrier action. High loading efficiency and capability were reached as verified through UV and TGA measurements. We report the first study of thymol effect on Xylella fastidiosa, conducing both fluorometric assay and in vitro inhibition assay. The first test confirmed the great antibacterial effect of this compound. Finally, an in vitro test revealed an interesting synergistic action of thymol and nanocarriers, suggesting the potential application of thymol-nanoparticles as effective biocides to control Xylella fastidiosa infection.

Essential oil-based pesticides, which contain antimicrobial and antioxidant molecules, have potential for use in sustainable agriculture. However, these compounds have limitations such as volatility, poor water solubility, and phytotoxicity. Nanoencapsulation, through processes like micro- and nanoemulsions, can enhance the stability and bioactivity of essential oils. In this study, thyme essential oil from supercritical carbon dioxide extraction was selected as a sustainable antimicrobial tool and nanoencapsulated in an oil-in-water emulsion system. The investigated protocol provided high-speed homogenisation in the presence of cellulose nanocrystals as stabilisers and calcium chloride as an ionic crosslinking agent. Thyme essential oil was characterised via GC-MS and UV-vis analysis, indicating rich content in phenols. The cellulose nanocrystal/essential oil ratio and calcium chloride concentration were varied to tune the nanoemulsions’ physical–chemical stability, which was investigated via UV-vis, direct observation, dynamic light scattering, and Turbiscan analysis. Transmission electron microscopy confirmed the nanosized droplet formation. The nanoemulsion resulting from the addition of crosslinked nanocrystals was very stable over time at room temperature. It was evaluated for the first time on Pseudomonas savastanoi pv. savastanoi, the causal agent of olive knot disease. In vitro tests showed a synergistic effect of the formulation components, and in vivo tests on olive seedlings demonstrated reduced bacterial colonies without any phytotoxic effect. These findings suggest that crosslinked cellulose nanocrystal emulsions can enhance the stability and bioactivity of thyme essential oil, providing a new tool for crop protection.

Hazelnut represents a relevant agro-food supply chain in many countries worldwide. Several biological adversities threaten hazelnut cultivation, but among them bacterial blight is one of the most feared and pernicious since its control can be achieved only by prevention through the observation of good agricultural practices and the use of cupric salts. The aim of this work was to evaluate the lignocellulosic biomasses obtained from hazelnut pruning and shelling residues as a renewable source of cellulose nanocrystals and lignin nanoparticles and to investigate their antimicrobial properties against hazelnut bacterial blight. Cellulose nanocrystals were obtained through an acid hydrolysis after a chemical bleaching, while lignin nanoparticles were synthesized by a solvent–antisolvent method after an enzymatic digestion. Both collected nanomaterials were chemically and morphologically characterized before being tested for their in vitro and in vivo antibacterial activity and biocompatibility on hazelnut plants. Results indicated the selected biomasses as a promising starting material for lignocellulosic nanocarriers synthesis, confirming at the same time the potential of cellulose nanocrystals and lignin nanoparticles as innovative tools to control hazelnut bacterial blight infections without showing any detrimental effects on the biological development of treated hazelnut plants.

Nanotechnology is rapidly gaining ground in crop protection, with the growing quest for sustainable nanopesticides and nanocarriers for plant pathogen management. Among them, cellulose nanocrystals (CNC) are emerging as innovative agrofood-waste-derived antimicrobial materials. In this work, new chemical and enzymatic CNC extraction methods from tomato harvest residues were evaluated. The obtained nanomaterials were characterized and tested for their antimicrobial properties on Pseudomonas syringae pv. tomato (Pto), the causal agent of bacterial speck disease on tomato. Both protocols were efficient. The enzymatic extraction method was greener, producing purer CNC at slightly lower yield. The obtained CNC, although they weakly inhibited cell growth and did not promote reactive oxygen species (ROS) formation, provoked bacterial aggregation and the inhibition of biofilm production and swimming motility. Both protocols produced CNC with similar morpho-chemical features, as well as promising antimicrobial activity against plant bacterial pathogens, suggesting their potential role in sustainable crop protection strategies. The new protocols could be a valuable alternative to conventional methods.