Nanocarrier (NC)‐mediated drug delivery is widely researched in medicine but to date has not been used in agriculture. The first curative NC‐based treatment of the worldwide occurring grapevine trunk disease Esca, with more than 2 billion infected plants causing a loss yearly of $1.5 billion, is presented. To date, only repetitive spraying of fungicides is used to reduce chances of infection. This long‐term treatment against Esca uses minimal amounts of fungicide encapsulated in biobased and biodegradable lignin NCs. A single trunk injection of <10 mg fungicide results in curing of an infected plant. Only upon Esca infection, ligninolytic enzymes, secreted by the Esca‐associated fungi, degrade the lignin NC to release the fungicide. The specific antifungal activity is confirmed in vitro and in planta (in Vitis vinifera L. cv. ‘Portugieser’). All treated plants prove to exhibit significantly fewer symptoms several weeks after treatment, and their condition is monitored for 5 years (2014–2018), proving a long‐term curative effect of this NC treatment. This study proves the efficacy of this NC‐mediated drug delivery for agriculture, using a minimum amount of fungicides. It is believed that this concept can be extended to other plant diseases worldwide to reduce extensive spraying of agrochemicals.

Lignin is an abundant biopolymer that is mainly burned for energy production today. However, using it as a polyfunctional macromolecular building block would be desirable. Herein, Kraft lignin was modified through esterification of its hydroxyl groups with methacrylic anhydride. Then lignin nanocarriers with different morphologies (solid nanoparticles, core–shell structures, porous nanoparticles) were produced by a combination of miniemulsion polymerization and a solvent evaporation process. A UV-active cargo is used as a drug model to investigate the release behavior of the lignin nanocarriers depending on their morphology. To prove the enzymatic response of the lignin nanocarriers, we tested the enzyme laccase as a trigger to release the encapsulated cargo. Furthermore, porous lignin nanoparticles with high surface area were produced by carbonization. The carbon material has a high potential as an adsorbent, which was studied by adsorption tests with methylene blue. These biodegradable nanocarriers based on the polyfunctional bioresource lignin may find useful application as novel drug delivery vehicle in agriculture or as carbon materials for water purification.

Lignin-based nano- and microcarriers are a promising biodegradable drug delivery platform inside of plants. Many wood-decaying fungi are capable of degrading the wood component lignin by segregated lignases. These fungi are responsible for severe financial damage in agriculture, and many of these plant diseases cannot be treated today. However, enzymatic degradation is also an attractive handle to achieve a controlled release of drugs from artificial lignin vehicles. Herein, chemically cross-linked lignin nanocarriers (NCs) were prepared by aza-Michael addition in miniemulsion, followed by solvent evaporation. The cross-linking of lignin was achieved with the bio-based amines (spermine and spermidine). Several fungicides—namely, azoxystrobin, pyraclostrobin, tebuconazole, and boscalid—were encapsulated in situ during the miniemulsion polymerization, demonstrating the versatility of the method. Lignin NCs with diameters of 200–300 nm (determined by dynamic light scattering) were obtained, with high encapsulation efficiencies (70–99%, depending on the drug solubility). Lignin NCs successfully inhibited the growth of Phaeomoniella chlamydospora and Phaeoacremonium minimum , which are lignase-producing fungi associated with the worldwide occurring fungal grapevine trunk disease Esca. In planta studies proved their efficiency for at least 4 years after a single injection into Vitis vinifera (“Portugieser”) plants on a test vineyard in Germany. The lignin NCs are of high interest as biodegradable delivery vehicles to be applied by trunk injection against the devastating fungal disease Esca but might also be promising against other fungal plant diseases.

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Spraying of agrochemicals (pesticides, fertilizers) causes environmental pollution on a million‐ton scale. A sustainable alternative is target‐specific, on‐demand drug delivery by polymeric nanocarriers. Trunk injections of aqueous nanocarrier dispersions can overcome the biological size barriers of roots and leaves and allow distributing the nanocarriers through the plant. To date, the fate of polymeric nanocarriers inside a plant is widely unknown. Here, the in planta conditions in grapevine plants are simulated and the colloidal stability of a systematic series of nanocarriers composed of polystyrene (well‐defined model) and biodegradable lignin and polylactic‐co‐glycolic acid by a combination of different techniques is studied. Despite the adsorption of carbohydrates and other biomolecules onto the nanocarriers’ surface, they remain colloidally stable after incubation in biological fluids (wood sap), suggesting a potential transport via the xylem. The transport is tracked by fluorine‐ and ruthenium‐labeled nanocarriers inside of grapevines by 19F‐magnetic resonance imaging or induced coupled plasma – optical emission spectroscopy. Both methods show that the nanocarriers are transported inside of the plant and proved to be powerful tools to localize nanomaterials in plants. This study provides essential information to design nanocarriers for agrochemical delivery in plants to sustainable crop protection.