Fungicide Formulations Influence Their Control Efficacy by Mediating Physicochemical Properties of Spray Dilutions and Their Interaction with Target Leaves

Biomass-Based, Dual Enzyme-Responsive Nanopesticides: Eco-friendly and Efficient Control of Pine Wood Nematode Disease

Pine wood nematode (PWN) disease is a globally devastating forest disease caused by infestation with PWN, Bursaphelenchus xylophilus, which mainly occurs through the vector insect Japanese pine sawyer (JPS), Monochamus alternatus. PWN disease is notoriously difficult to manage effectively and is known as the "cancer of pine trees." In this study, dual enzyme-responsive nanopesticides (AVM@EC@Pectin) were prepared using nanocoating avermectin (AVM) after modification with natural polymers. The proposed treatment can respond to the cell wall-degrading enzymes secreted by PWNs and vector insects during pine tree infestation to intelligently release pesticides to cut off the transmission and infestation pathways and realize the integrated control of PWN disease. The LC50 value of AVM@EC@Pectin was 11.19 mg/L for PWN and 26.31 mg/L for JPS. The insecticidal activity of AVM@EC@Pectin was higher than that of the commercial emulsifiable concentrate (AVM-EC), and the photostability, adhesion, and target penetration were improved. The half-life (t1/2) of AVM@EC@Pectin was 133.7 min, which is approximately twice that of AVM-EC (68.2 min). Sprayed and injected applications showed that nanopesticides had superior bidirectional transportation, with five-times higher AVM contents detected in the roots relative to those of AVM-EC when sprayed at the top. The safety experiment showed that the proposed treatment had lower toxicity and higher safety for nontarget organisms in the application environment and human cells. This study presents a green, safe, and effective strategy for the integrated management of PWN disease.

Ascendancy of pyraclostrobin nanocapsule formulation against Rhizoctonia solani: From a perspective of fungus

High-performance pesticide formulations are essential for sustainable agriculture. Among these, nano-pesticides exhibit great advantages in pest control because of their unique size effects. However, the direct effects of nano-formulation fungicides on fungal pathogens remain largely unexplored. In this study, three qualified formulations, suspension concentrate (SC), microcapsules (CS), and nanocapsules (NCS) of pyraclostrobin (PYR) were prepared and utilized to reveal their biocontrol activities against Rhizoctonia solani. Among these three formulations, NCS exhibited notable biocontrol efficacy against R. solani exemplified by an EC50 of 0.319 mg/L for mycelia, distortion of mycelia and abnormalities in cell ultrastructure. Moreover, NCS displayed excellent internalization within R. solani mycelia, contributing to severe damage to cell membrane permeability. Importantly, an equivalent quantity of NCS-PYR showed potent inhibitory effects on the target pathogen, as indicated by reduced adenosine triphosphate (ATP) content and mitochondrial Complex III activity. The NCS consistently exhibited superior in vivo protective and curative activities against R. solani compared to those of CS and SC in rice and faba bean. In summary, we uncovered the strength of rapid efficacy and biocontrol activity of NCS against R. solani and elucidated the advantages of NCS-PYR from the perspective of the target pathogen in agriculture.

Using a Dynamic Hydrophilization Strategy to Achieve Nanodispersion, Full Wetting, and Precise Delivery of Hydrophobic Pesticide

Various strategies have been developed to improve the applicability of hydrophobic pesticides for better effectiveness in agriculture. However, existing formulations of hydrophobic pesticides still suffer from complicated processing, abused organic solvents, indispensable surfactants, or inescapable ecotoxicity, which strictly limit their applications. Herein, a dynamic covalent bond tailored pesticide (fipronil) amphiphile is constructed to address the above issues, which accomplishes the nanodispersion, full wetting, and precise delivery without organic solvents, surfactants, and materials simultaneously. By introducing a hydrophilic ligand on the hydrophobic fipronil through an imine bond, the cleavable fipronil amphiphile (FPP) exhibits superior water solubility and can even self-assemble into micelles at higher concentrations, which can be directly applied in powder form without organic solvents. Attributed to the suitable hydrophilic/hydrophobic ratio, FPP achieves full wetting and effective deposition on superhydrophobic rice leaves without surfactants. Moreover, benefiting from the unique dynamic nature of the imine bond, FPP maintains good storage stability while sensitively releasing back to fipronil under the humidity and pH trigger, consequently implementing the precise delivery for nontarget Apis cerana and target Chilo suppressalis without materials. To our knowledge, this dynamic covalent bond tailored amphiphile strategy is the first idea that simultaneously takes the dispersibility, wettability, and responsiveness of hydrophobic pesticides into account, providing a possibility to control the entire journey of field application and even promising to be incorporated into the synthesis process, thus paving the way for modern sustainable agriculture.

Amphiphilicity-Driven Small Alcohols Regulate the Flexibility of Pesticide-Loaded Microcapsules for Better Foliar Adhesion and Utilization

The foliar loss of pesticides causes serious utilization decline and environmental risk. On the basis of biomimetics, pesticide-loaded microcapsules (MCs) with spontaneous deformation on foliar micro/nanostructures, like the snail suction cup, are prepared by interfacial polymerization. By controlling the usage or types of small alcohols in the MC preparation system, the flexibility of MCs is tunable. Through the investigation of emulsions and MC structures, we discover that the migration and distribution of small alcohols driven by amphiphilicity affect the process of interfacial polymerization between polyethylene glycol and 4,4-methylenediphenyl diisocyanate. By hydrophobic modification of the polymer and competition for oil monomers of small alcohols, the thickness and compactness of shells are reduced, whereas the density of the core is increased. As a result of the regulation in structures, the flexibility of MCs is improved significantly. In particularly, the MCs-N-pentanol (0.1 mol kg^-1) with the best flexibility show strong scouring resistance on varied foliar structures, sustained release property on the air/solid interface, and persistent control effect against foliar diseases. The pesticide-loaded soft MCs provide an effective way to improve pesticide foliar utilization.

pH-responsive release and washout resistance of chitosan-based nano-pesticides for sustainable control of plumeria rust

Controlled pesticide release in response to environmental stimuli by encapsulating pesticides in a carrier is a feasible approach to improve the effective utilization rate. In this study, pH-responsive release nanoparticles loaded with penconazole (PE) were prepared by ionic cross-linking of chitosan and carboxymethyl chitosan (PE@CS/CMCS-NPs). PE@CS/CMCS-NPs exhibited good washout resistance and wettability properties, increasing the washing resistance of the pesticide by approximately 20 times under continuous washing. The results of the release experiments showed that nanoparticles had adjustable controlled-release characteristics with the change in pH based on the swelling of nanoparticles. The results of spore germination experiments showed that PE@CS/CMCS-NPs enhanced the inhibitory effect under acidic conditions. The field experiment results showed that PE@CS/CMCS-NPs had a better control effect than PE-aqueous solution, extended the duration and slowed down the dissipation of PE. These results indicated that the CS/CMCS-NPs pH-responsive release system has great potential in the development of an effective pesticide formulation.

Different leaf-mediated deposition, absorbed and metabolism behaviors of 2,4-D isooctyl ester between Triticum aestivum and Aegilops tauschii Coss

Tausch's goatgrass (Aegilops tauschii Coss.), is a major weed species, infesting wheat (Triticum aestivum) fields in China. 2,4-D isooctyl ester is widely used for broadleaf weed control and selected as a tool to study the differences between, A. tauschii and T. aestivum. In this study, we measured the growth responses of these species to 2,4-D isooctyl ester and found that T. aestivum was more sensitive to the herbicide than A. tauschii. To clarify the reasons for this difference, we measured the leaf-mediated deposition, absorption and metabolism of 2,4-D isooctyl ester and the expression of auxin receptor transport inhibitor response (TIR1) gene in T. aestivum and A. tauschii. The results indicated that the deposition of 2,4-D isooctyl ester droplets may be lower on A. tauschii than on T. aestivum, because of the increased contact angle and greater density of trichomes on the leaves of the former. A distinct increase in 2,4-D isooctyl ester uptake was detected in T. aestivum during the entire experimental period, and the rate was 2.2-fold greater than that in A. tauschii at 6 h after treatment. Compared with A. tauschii, T. aestivum exhibited a greater accumulation of primary metabolite 2,4-D in plants, which may be responsible for the different responses of the two species. Additionally, the absolute expression level of TIR1 was clearly greater in T. aestivum than that in A. tauschii. These data will be helpful to further understand the differences between T. aestivum and A. tauschii, which may provide a unique perspective for the development and identification of new target compounds that are effective against this weed species.

Residue and dissipation of two formulations of emamectin benzoate in tender cowpea and old cowpea and a risk assessment of dietary intake

The dissipation and residue levels of emamectin benzoate emulsifiable concentrate (EC) and microemulsion (ME) formulations in tender cowpeas and old cowpeas were investigated under field conditions. The decline curves of emamectin benzoate residues in cowpea corresponded to first-order kinetics. The dissipation rate of emamectin benzoate in tender cowpeas was faster than that in old cowpeas. The half-lives of the EC were 1.34-1.39 d and 1.74-2.31 d in tender cowpea and old cowpea, respectively. For the ME, the half-lives were 1.39-1.51 d and 2.08-2.67 d, respectively. The risk of adult intake of emamectin benzoate from cowpea is within the acceptable limits of the human body. Compared to tender cowpeas, the risk of eating old cowpeas is higher. Emamectin benzoate (EC) is recommended for cowpeas when the intention is to harvest tender cowpeas, while both formulations are acceptable for cowpeas when the intention is to harvest old cowpeas.

Impact of the equilibrium relationship between deposition and wettability behavior on the high-efficiency utilization of pesticides

BACKGROUND

Often, due to the occurrence of powdery mildew, cucumber leaf surfaces is changed into a more hydrophobic surface, which affects wetting and spreading of liquid pesticides, reducing their efficiency. The wetting and deposition behavior of liquid pesticides can be improved by adding surfactants to pesticides. Added surfactants affect the spray volume of the pesticide, which can lead to waste and a low utilization rate of the pesticide. It is important to further balance the relationship between deposition and wettability of pesticide liquid on the surfaces of healthy leaves and powdery mildew leaves of cucumber.

RESULTS

This study evaluated the deposition and wettability of hexaconazole (Hexa) with surfactants on the surfaces of healthy leaves and powdery mildew leaves of cucumber. The deposition rates of Hexa with surfactants were lower than that of Hexa due to the loss of solution in conventional spray volume (750 L ha^-1 ). The deposition rate of Hexa did not necessarily increase with increasing spray volume, and the deposition rate did not increase again after the spray volume increased to a certain level. Under the condition that the prevention and control effect were not reduced, we found that the volume of solution spray with added Silwet618 or AEO-5 should be adjusted to half of the normal volume, while the volume of solution spray with added 1227 or rosin-based quarternary ammonium should be adjusted to two-thirds of the normal volume to increase the deposition rate by approximately 30%. Regarding the wetting parameters, the results showed that the wettability of Hexa with Silwet618 was the best, but their combination was not ideal according to the composite index and deposition. By analyzing all the parameters, it was found that the spray volume reduction of Hexa with surfactant was approximately equal to the solution surface tension reduction, compared with the parameters of Hexa.

CONCLUSION

The equilibrium relationship between deposition rate and wetting parameters was determined to provide guidance for the application of surfactants and to lower the dosage of pesticides to increase their efficiency and reduce their application. © 2021 Society of Chemical Industry.

Tank-mixing adjuvants enhanced the efficacy of fludioxonil on cucumber anthracnose by ameliorating the penetration ability of active ingredients on target interface

In this study, pot and field experiments showed that S903, Hasten and Gemini-31511 can significantly enhanced the control efficacy of fludioxonil on cucumber anthracnose. Then by studying the deposition and penetration interaction between active ingredients and cucumber leaves to revealed how the adjuvants influence the interaction process between pesticide active ingredients and target plants to improve the control efficacy. By analysis the effect of fludioxonil deposition to synergism of adjuvants, indicated that fludioxonil active ingredient deposition caused by adjuvants was not the main factor for the adjuvants synergistic effect. Fludioxonil + S903 yielded the lowest surface tension and contact angle, which also implying the best wetting ability. The mean diameters in Hasten + fludioxonil group were much smaller than those in only fludioxonil group (5.39 μm-90 g a.i. ha^-1, 5.50 μm-180 g a.i. ha^-1), the average particle size only had 3.45 μm (90 g a.i. ha^-1) and 3.94 μm (180 g a.i. ha^-1). And the result of spray droplets was consistent with the particles of fludioxonil crystals observed on glass slides and cucumber leaves. Therefore, S903 improved the penetrability of fludioxonil in the target plants by improving the wetting and dispersion of active ingredients on the target interface. Meantime, Hasten improved the penetrability of fludioxonil in the target plants by decreasing the particle size of active ingredients.

Dissipation kinetics and safety evaluation of pyraclostrobin and its desmethoxy metabolite BF 500-3 in a cucumber greenhouse agroecosystem

Pyraclostrobin (PYR), a fungicide of the strobilurin class, is used to control many different kinds of fungal diseases in greenhouses and on agricultural fields. In the present study, an efficient method was established for simultaneously determining PYR and its metabolite BF 500-3 in cucumber fruits, leaves, and soil matrices using QuEChERS pretreatment coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The residue levels and dissipation kinetics of PYR were determined under greenhouse conditions. The recoveries ranged from 89.8 to 103.6% with relative standard deviations (RSDs) of 3.6-7.5% at three spiking levels. The results demonstrated that PYR dissipated quickly in the cucumber field with half-lives (DT₅₀) of 2.14-4.17 days on different sites and in different matrices. The residue of its metabolite BF 500-3 was very low and showed a trend of first increasing and then decreasing. The degradation rate of PYR in soil was the fastest, followed by that on cucumber fruits and leaves. The terminal residue of PYR at an application rate of 150 g a.i. ha^-1 (the maximum recommended rate) in cucumber fruits was below the maximum residue limit (MRL) of 0.5 mg/kg established in China. However, the application of the fungicide at 225 g a.i. ha^-1 (1.5× the maximum recommended rate) resulted in residues that were above the MRL 1 day after the final application, which is an unacceptable risk. Therefore, the application dosage of PYR at the recommended rates was safe to human beings and animals.

Determination of pyraclostrobin dynamic residual distribution in tilapia tissues by UPLC-MS/MS under acute toxicity conditions

As a lipophilic fungicide, pyraclostrobin is highly toxic to aquatic organisms, especially to fish. In recent years, research has mainly focused on the pyraclostrobin residue in fish tissues under chronic toxicity, but less is known about its distribution in fish tissues under acute toxicity conditions. In this study, the distribution of pyraclostrobin in fish tissues (blood, liver, muscle and gill) was determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The purification effects of different purification materials [1) mixtures of PSA, C₁₈ and MgSO₄; 2) QuEChERS-PC; and 3) Oasis HLB SPE] were compared for the detection of pyraclostrobin in fish tissues. Finally, the quick and easy clean-up tool of the Oasis HLB SPE procedure was selected. Under optimum conditions, the linearities had a good relationship (determination coefficient R² > 0.999). The mean recoveries of the analyte for all tested concentrations ranged from 86.94% to 108.81% with RSDs of 0.7%-4.9%. The pyraclostrobin residue amount was much different in fish tissues. Furthermore, the pyraclostrobin residue in different fish tissues increased initially and then decreased gradually. The concentrations in each tissue were initially ranked before 120 min in the following order: gill > liver > blood > muscle. These phenomena may be attributed to the stress response of fish under acute poisoning. This is the first study to document the distribution of pyraclostrobin in fish tissues under acute toxicity conditions, and it provides reference for the management of agrochemicals in terms of aquatic ecological risks.