Self-Assembled Nanoparticles of a Prodrug Conjugate Based on Pyrimethanil for Efficient Plant Disease Management.

Self-assembled nanotechnology is a promising strategy for improving the effective utilization of pesticides due to its distinct advantages. Herein, an amide-bonded prodrug conjugate based on pyrimethanil (PYR) and butyric acid (BA) was successfully synthesized by the nucleophilic substitution reaction and subsequently self-assembled into spherical nanoparticles (PB NPs) with an average size of 85 nm through the solvent exchange method without using any toxic adjuvant. The results showed that PB NPs based on PYR and BA had a synergistic antimicrobial activity against S. sclerotiorum on plant leaves due to good photostability, low volatilization, good surface activity, and improved retention. Additionally, PB NPs could be used by plant cells as nutrients to promote the growth of plants and thus reduced the toxicity of PYR to plant. Therefore, this prodrug conjugate self-assembly nanotechnology would provide a promising strategy for improving the effective utilization rates of pesticides and reducing their toxicities to plants.

Pectin functionalized metal-organic frameworks as dual-stimuli-responsive carriers to improve the pesticide targeting and reduce environmental risks.

Encapsulation of active ingredients into intelligent response controlled release carriers has been recognized as a promising approach to enhance the utilization efficiency and reduce the environmental risks of pesticides. In this work, an intelligent redox and pectinase dual stimuli-responsive pesticide delivery system was constructed by bonding pectin with metal-organic frameworks (FeMOF nanoparticles) which were loaded with pyraclostrobin (PYR@FeMOF-pectin nanoparticles). The successful fabrication of PYR@FeMOF-pectin nanoparticles was proved by a series of physicochemical characterizations. The results indicated that the loading capacity of PYR@FeMOF-pectin nanoparticles for pyraclostrobin was approximately 20.6%. The pectin covered on the surface of PYR@FeMOF nanoparticles could protect pyraclostrobin from photolysis and improve their spreadability on rice blades effectively. Different biological stimuli associated with Magnaporthe oryzae could trigger the release of pyraclostrobin from the pesticide-loaded core-shell nanoparticles, resulting in the death of pathogens. The bioactivity survey determined that PYR@FeMOF-pectin nanoparticles had a superior fungicidal activity and a longer duration against Magnaporthe oryzae than pyraclostrobin suspension concentrate. In addition, the FeMOF-pectin nanocarriers showed no obvious phytotoxicity and could enhance the shoot length and root length of rice plants. More importantly, PYR@FeMOF-pectin nanoparticles had an 8-fold reduction in acute toxicity to zebrafish than that of pyraclostrobin suspension concentrate. Therefore, the dual-responsive FeMOF-pectin nanocarriers have great potential for realizing site-specific pesticide delivery and promoting plant growth.

Pectin-conjugated silica microcapsules as dual-responsive carriers for increasing the stability and antimicrobial efficacy of kasugamycin.

Kasugamycin is an aminoglycoside antibiotic originally isolated from Streptomyces kasugaensis, which has been widely used for the management of plant diseases. However, photo-thermal instability and low efficiency limit its application. Therefore, it is an urgent task to prevent unwanted loss of kasugamycin and ensure maximum bioactivity at target site. In this work, a novel formulation of kasugamycin that responds to different biological stimuli produced by pests was prepared using silica microcapsules crosslinked with pectin via special disulfide bonds. The results demonstrated that the silica-SS-pectin microcapsules had a high loading efficiency (20% w/w) and could effectively enhance the thermal and light stability of kasugamycin. The microcapsules displayed excellent pectinase and glutathione dual-responsive properties and the release kinetics investigated by Riger-Peppas model suggested combination of various release mechanisms. Compared with kasugamycin wettable powder, the microcapsules possessed sustained and improved antimicrobial efficacy against Erwinia carotovora. Thus, the dual-responsive microcapsules potentially have agricultural application as a controlled release system.

Synthesis, characterization, and application of microbe-triggered controlled-release kasugamycin-pectin conjugate.

The controlled and targeted release of pesticides with high water solubility has been a challenge for integrated pest management. In this paper, kasugamycin, an antibiotic broadly used in plant disease control, was covalently conjugated to pectin to form a kasugamycin-pectin conjugate by an amide bond. The conjugate was structurally characterized by Fourier transform infrared spectroscopy, ultraviolet spectrophotometry, and thermal gravimetric analysis. The results showed that the conjugate was stable over a wide range of pH and temperatures, as well as under UV irradiation. When incubated with Pseudomonas syringae pv. lachrymans, the conjugate could be activated, releasing the kasugamycin, which made it a promising controlled-release formulation of pesticide.

Evaluation of the efficacy of glyphosate plus urea phosphate in the greenhouse and the field.

BACKGROUND: Glyphosate is a non-selective, foliar-applied, systemic herbicide that kills weeds by inhibiting the synthesis of 5-enolpyruvylshikimate-3-phosphate synthase. Urea phosphate (UPP), made by the reaction of urea with phosphoric acid, was applied as an adjuvant for glyphosate in this study. Experiments in the greenhouse and the field were conducted to determine the effects of UPP by comparing the efficacies of glyphosate plus UPP, glyphosate plus 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS) and Roundup. RESULTS: The optimum concentration of UPP in glyphosate solution was 2.0% when UPP was used as an adjuvant. The ED50 values for glyphosate-UPP were 291.7 and 462.4 g AI ha(-1) in the greenhouse and the field respectively, while the values for Roundup were 448.2 and 519.6 g AI ha(-1). The ED50 values at 2 weeks after treatment (WAT) and 3 WAT were lowered when UPP was used as an adjuvant in the greenhouse and field study, and the glyphosate+UPP was absorbed over a 2 week period. UPP may increase the efficacy by causing severe cuticle disruption or accelerating the initial herbicide absorption. The result also showed that UPP could reduce the binding behaviour of Ca2+ to glyphosate. CONCLUSION: The application of UPP as an adjuvant could increase the efficacy of glyphosate and make it possible to achieve effective control of weeds with glyphosate at lower dose. Moreover, UPP showed less causticity to spraying tools and presented less of a health hazard. Therefore, UPP is accepted as being a new, effective and environmentally benign adjuvant for glyphosate.