Screening structure and predicting toxicity of pesticide adjuvants using molecular dynamics simulation and machine learning for minimizing environmental impacts.

Surfactants as synergistic agents are necessary to improve the stability and utilization of pesticides, while their use is often accompanied by unexpected release into the environment. However, there are no efficient strategies available for screening low-toxicity surfactants, and traditional toxicity studies rely on extensive experimentation which are not predictive. Herein, a commonly used agricultural adjuvant Triton X (TX) series was selected to study the function of amphipathic structure to their toxicity in zebrafish. Molecular dynamics (MD) simulations, transcriptomics, metabolomics and machine learning (ML) were used to study the toxic effects and predict the toxicity of various TX. The results showed that TX with a relatively short hydrophilic chain was highly toxic to zebrafish with LC50 of 1.526 mg/L. However, TX with a longer hydrophilic chain was more likely to damage the heart, liver and gonads of zebrafish through the arachidonic acid metabolic network, suggesting that the effect of surfactants on membrane permeability is the key to determine toxic results. Moreover, biomarkers were screened through machine learning, and other hydrophilic chain lengths were predicted to affect zebrafish heart health potentially. Our study provides an advanced adjuvants screening method to improve the bioavailability of pesticides while reducing environmental impacts.

Salinity-Driven Interface Self-Assembly of a Biological Amphiphilic Emulsifier to Form Stable Janus Core-Shell Emulsion for Enhancing Agrichemical Delivery.

Agrichemical losses are a severe threat to the ecological environment. Additionally, some agrichemical compounds contain abundant salt, which increases the instability of formulations, leading to a lower agrichemical utilization and soil hardening. Fortunately, the biological amphiphilic emulsifier sodium deoxycholate alleviates these problems by forming stable Janus core-shell emulsions through salinity-driven interfacial self-assembly. According to the interfacial behavior, dilational rheology, and molecular dynamics simulations, Janus-emulsion molecules are more closely arranged than traditional-emulsion molecules and generate an oil-water interfacial film that transforms into a gel film. In addition, at the same spray volume, the deposition area of the Janus emulsion increased by 37.70% compared with that of the traditional emulsion. Owing to the topology effect and deformation, the Janus emulsion adheres to rice micropapillae, achieving better flush resistance. Meanwhile, based on response of the Janus emulsion to stimulation by carbon dioxide (CO2), the emulsion lost to the soil can form a rigid shell for inhibiting the release of pesticides and metal ions from harming the soil. The pyraclostrobin release rate decreased by 50.89% at 4 h after the Janus emulsion was exposed to CO2. The Chao1 index of the Janus emulsion was increased by 12.49% as compared to coconut oil delivery in soil microbial community. The Janus emulsion ingested by harmful organisms can be effectively absorbed in the intestine to achieve better control effects. This study provides a simple and effective strategy, which turns waste into treasure, by combining metal ions in agrichemicals with natural amphiphilic molecules to prepare stable emulsions for enhancing agrichemical rainfastness and weakening environmental risk.

Promising Delivery Platform for Smart Pest Control with High Water-Retaining Capacity.

Hydrogels have been extensively used in agriculture to improve crop yields for their excellent properties. However, they are currently used either as pesticide delivery platforms or water retention agents alone; the combination of these two functions into one agricultural hydrogel formulation has never been reported, which is crucial to promote sustainable development in agriculture. Herein, using poly(ß-cyclodextrin) and adamantane-grafted poly(acrylic acid) (PAA-Ada) as the host and guest, respectively, an easy operating, multi-responsive, and safer hydrogel delivery system for insecticides is fabricated by the host-guest interaction between cyclodextrin and adamantane, which can load uniformly dispersed insecticides (fipronil, imidacloprid, and thiamethoxam) up to 60%. Benefiting from the carboxyl and hydroxyl groups on polymer chains, different temperatures (25, 35, and 45 °C) and pH values (5.0, 6.8, and 10.0) change the intermolecular forces within the hydrogel network and then the diffusion of the content, finally resulting in controlled release behaviors. Besides, this platform can rapidly release the insecticides in the presence of amyloglucosidase due to its ring-opening effect on cyclodextrin. Moreover, this platform exhibits high water-retaining capacity toward soil, which can increase the maximum water absorption of nutrient soil and quartz sand by 31.6 and 13.9%, respectively, and slows down the water loss. Compared with commercial formulation, this smart system reduces the acute toxicity to non-target organism earthworms by 52.4% and improves the efficacy against target organism aphids by 47.3%, showing better durability, lower environmental toxicity, and higher efficiency. To our knowledge, this is the first idea that simultaneously adopts the water-retaining capacity and controlled release ability of hydrogels to improve insecticide efficacy. In this regard, this smart hydrogel platform holds great potentials as slow-release granules with water-holding ability for protection against insect pests, providing an alternative platform for the sustainable development in green agriculture.

The simple strategy to improve pesticide bioavailability and minimize environmental risk by effective and ecofriendly surfactants.

Low pesticide efficiency has caused serious environmental pollution and economic loss, which are closely related to each link in the targeted delivery of pesticides. However, the existing strategies for improving pesticide utilization rate are not comprehensive, and the regulation of foliar absorption and biological activity has been neglected. As surfactants are the most important agricultural synergists, the impact, wetting, adhesion, and leaf retention behaviors of pyraclostrobin (PYR) droplets containing the surfactant Triton X (TX) series on hydrophobic scallion leaf surfaces were studied. The results showed that TX-102 can sufficiently reduce the splash and roll of droplets when they impact inclined leaves, owing to its low dynamic surface tension. Moderate wetting ability and high adhesion also maximizes leaf retention of the TX-102-added PYR solution sprayed on scallion leaves. Furthermore, TX-102 improved the permeation and absorption of PYR in scallion leaves through the synergistic effects of opening the stomata and dissolving the waxy layer. The synergistic bioactivity of TX-102 against pathogenic fungi Alternaria porri and its safety to non-target organism zebrafish have also been demonstrated. Our study provides a more comprehensive theoretical rationale for screening adjuvants to improve the effectiveness and bioavailability of pesticides and reduce the risk of pesticides entering the environment.

Surface properties of Tetranychus urticae Koch (Acari: Tetranychidae) and the effect of their infestation on the surface properties of kidney bean (Phaseolus vulgaris L.) hosts.

BACKGROUND: The wettability of the target surfaces affects the wetting and deposition of pesticides on them. The properties of leaf surfaces change after infestation by Tetranychus urticae Koch. Studying the surface wettability of T. urticae and the changes in leaf wettability after infestation is important to guide the use of acaricides. RESULTS: The body surface of T. urticae is an ellipsoidal crown covered with dense cuticle striations and hairs arranged in different directions, which makes the surface of T. urticae rough and hydrophobic. The abaxial surfaces of the leaves are rougher and more hydrophobic than the adaxial surfaces. After infestation by T. urticae, the faded spots were sunken on the adaxial surface and raised on the abaxial surface, where they had formed new wide peaks and valleys. The adaxial surface became obviously rougher and more hydrophobic, while the roughness of the abaxial surface became slightly larger, and the change in hydrophobicity was not obvious. The contact angles of the studied commercial acaricide on these surfaces were greater than 65° and were affected by the infestation. Reducing the surface tension can allow for better wetting of these surfaces and eliminate changes in leaf wettability. CONCLUSION: The surfaces of kidney bean leaves became more hydrophobic after infestation by T. urticae with hydrophobic surface. The wettability of the acaricide solution should be adjusted according to the changes in leaf wettability. This study has important theoretical guiding significance for improving effective deposition of acaricide.