Enantioselective dissipation of pyriproxyfen in soils and sand

The promoting effects of pyriproxyfen on autophagy and apoptosis in silk glands of non-target insect silkworm, Bombyx mori

Pyriproxyfen is a juvenile hormone analogue. The physiological effects of its low-concentration drift during the process of controlling agricultural and forestry pests on non-target organisms in the ecological environment are unpredictable, especially the effects on organs that play a key role in biological function are worthy of attention. The silk gland is an important organ for silk-secreting insects. Herein, we studied the effects of trace pyriproxyfen on autophagy and apoptosis of the silk gland in the lepidopteran model insect, Bombyx mori (silkworm). After treating fifth instar silkworm larvae with pyriproxyfen for 24 h, we found significant shrinkage, vacuolization, and fragmentation in the posterior silk gland (PSG). In addition, the results of autophagy-related genes of ATG8 and TUNEL assay also demonstrated that autophagy and apoptosis in the PSG of the silkworm was induced by pyriproxyfen. RNA-Seq results showed that pyriproxyfen treatment resulted in the activation of juvenile hormone signaling pathway genes and inhibition of 20-hydroxyecdysone (20E) signaling pathway genes. Among the 1808 significantly differentially expressed genes, 796 were upregulated and 1012 were downregulated. Among them, 30 genes were identified for autophagy-related signaling pathways, such as NOD-like receptor signaling pathway and mTOR signaling pathway, and 30 genes were identified for apoptosis-related signaling pathways, such as P53 signaling pathway and TNF signaling pathway. Further qRT-PCR and in vitro gland culture studies showed that the autophagy-related genes Atg5, Atg6, Atg12, Atg16 and the apoptosis-related genes Aif, Dronc, Dredd, and Caspase1 were responsive to the treatment of pyriproxyfen, with transcription levels up-regulated from 24 to 72 h. In addition, ATG5, ATG6, and Dronc genes had a more direct response to pyriproxyfen treatment. These results suggested that pyriproxyfen treatment could disrupt the hormone regulation in silkworms, promoting autophagy and apoptosis in the PSG. This study provides more evidence for the research on the damage of juvenile hormone analogues to non-target organisms or organs in the environment, and provides reference information for the scientific and rational use of juvenile hormone pesticides.

Environmental implication and cancer risk assessment of residual pollutants in cotton crop: a case study of Multan District, Pakistan

Pakistan is the fourth largest yarn producer in the world heavily that relies on cotton crop which receives a substantial 62% of all pesticide applications. The present study was conducted to quantify the levels of pesticides such as bifenthrin, spirotetramat, pyriproxyfen, imidacloprid, and diafenthiuron in soil and plants residue at selected cotton fields of Multan District, Pakistan. In addition to pesticides, the assessment of heavy metal concentration was also conducted in order to determine the overall risks that these compounds to both plants and human population. For this analysis, 20 soil samples and 10 plant samples were collected from 10 selected cotton fields. Pesticides and heavy metals in soil and plant samples were analyzed using high-performance liquid chromatography (HPLC) and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), respectively. It was observed that all samples collected from selected fields contained pesticide residue in top soil (0-15 cm). However, no pesticides were detected in the lower soil layer (16-30 cm). In case of heavy metals, the highest concentration of Fe, Pb, and Mn was observed in both soil and plant residue samples. The heavy metals were found in the order of Fe > Mn > Pb > Zn > Cu > Cd in the soil. The total carcinogenic risk values for a few pesticides were found to range from 10-6 to 10-2, indicating that residents of the study area have low to higher chances of developing cancer. A positive correlation was observed among the pesticides (r = 0.18-0.95) as well as in metals related parameters (r = 0.49-0.96), where a weak negative correlation was found among metal to pesticide parameters except Pd where the maximum r value was 0.62. In general, the finding of this study encourages the development and adoption of sustainable agricultural practices that lower the dependence on toxic pesticides and endorse environmentally friendly alternatives.

Persistence, leaching and associated toxicity risks of insecticide pyriproxyfen in soil ecosystem

Pyriproxyfen is a pyridine-based insecticide used for pest control in fruits and vegetables. It is a potent endocrine disruptor and hormone imitator. Considering its potential hazards to non-target organisms and the associated environment, a lab study was conducted for assessing persistence, mobility in sandy loam soil and associated risk to various non-target organisms and soil enzymes. Pyriproxyfen formulation was applied at 0.05 and 0.10 µg g^-1 soil which was equivalent to recommended and double dose of 100 and 200 g a.i. ha^-1, respectively. Three methods namely QuEChERS, liquid-solid extraction (LSE) and matrix solid phase dispersion (MSPD) were compared for achieving efficient sample preparation. MSPD was applied for final analysis as it gave better recoveries (94.2 to 104.3%) over other methods with limits of detection and quantification (LOD and LOQ) as 0.0001 and 0.0005 µg g^-1, respectively. Dissipation followed first order kinetics with half-lives of 7.6 and 8.2 days in both doses but residues retained over 45 days in soil. Leaching studies conducted at 50 and 100 µg of pyriproxyfen showed extremely poor leaching potential. Retention of over 90% residues in top 5 cm soil surface indicated minimal threat of ground and surface water contamination. Toxicological study demonstrated very different behaviour toward different enzymatic activities. Pyriproxyfen was relatively toxic for alkaline phosphatase and fluorescein diacetate hydrolase enzymes. β-glucosidase activity was triggered whereas arylsulfatase activity remained unaffected. Unacceptable risk to soil invertebrates at double dose application clearly indicated that its longer persistence in soil could be toxic to other non-target organisms and needs further investigations.

Systemic assessment of the chiral insecticide pyriproxyfen in a citrus nectar source system: Stereoselective degradation, biological effect and exposure risk

BACKGROUND

Balancing the safety and efficiency of chiral pesticides can help protect pollinators. We evaluated the stereoselective behavior, bioactivity, toxicity and exposure risk of the chiral insecticide pyriproxyfen in a citrus nectar system.

RESULTS

Density functional theory (DFT) and ultra-performance liquid chromatography tandem mass spectroscopy (UPLC-MS/MS) were applied for absolute configuration appraisal and chiral analysis validation, respectively. The recoveries ranged from 72.3% to 100.5% with an relative standard deviation (RSD) ranging from 1.2% to 9.7%. In a field trial, we determined insecticide half-lives in citrus leaves and flowers, which were 7.0 and 8.6 days for R-(+)-pyriproxyfen, and 11.7 and 14.7 days for S-(-)-pyriproxyfen, respectively. We found that the bioactivity of R-(+)-pyriproxyfen was 3.39 and 2.37 times higher than S-(-)-pyriproxyfen against Unaspis yanonensis and Diaphorina citri nymphs, respectively. S-(-)-pyriproxyfen had 3.8 times higher acute toxicity than R-(+)-pyriproxyfen on Apis mellifera L., and its exposure risk was moderate based on the hazard quotient.

CONCLUSION

The phenomenon of stereoselective degradation and biological effect demonstrated that the high-risk stereoisomer of S-(-)-pyriproxyfen degraded more slowly than R-(+)-pyriproxyfen, but R-(+)-pyriproxyfen with better efficiency for target. Therefore, an increased duration of R-(+)-pyriproxyfen activity on citrus was beneficial for efficacy. Our results could guide the scientific application and evaluation of chiral pesticides on nectar plants. © 2022 Society of Chemical Industry.

LC-MS/MS method for the simultaneous quantification of pyriproxyfen and bifenthrin and their dissipation kinetics under field conditions in chili and brinjal

Bifenthrin, a synthetic pyrethroid, and pyriproxyfen, a plant growth regulator, are used extensively in agriculture for controlling the different insect pests. The present study was undertaken to examine the dissipation behavior of a formulation with a combination of pyriproxyfen and bifenthrin on chili and brinjal under field conditions at four different locations. Dissipation study of combination of pyriproxyfen and bifenthrin revealed swift degradation in both crops with a half-life of 2.5-2.6 and 2.0-2.1 days in brinjal and chili, respectively. Also, a simple method for simultaneous quantification of pyriproxyfen and bifenthrin was developed and validated using modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) technique on liquid chromatography with tandem mass spectrometry (LC-MS/MS). Recovery of the method was found to be under an acceptable range of 90.0%-93.5% and 88.7%-94.3% in chili and 92.4%-96.6% and 97.4%-100.9% in brinjal for pyriproxyfen and bifenthrin, respectively. At harvest time, the terminal residues of bifenthrin and pyriproxyfen were below the maximum residue limits set by European Union in chili and brinjal, respectively, suggesting that the use of this pesticide formulation is safe and does not impose harmful effects on human health. PRACTICAL APPLICATION: In this paper, dissipation behavior of a pesticide formulation with a combination of pyriproxyfen and bifenthrin was undertaken under field conditions at four different locations on chili and brinjal in India. The simultaneous quantification of pyriproxyfen and bifenthrin using LC-MS/MS technique has been validated incorporating modified QuEChERS extraction method with limit of detection at 0.005 µg/g and limit of quantification at 0.01 µg/g, which is well below the EU-MRLs (European Union legislation Maximum Residue Level) of pyriproxyfen and bifenthrin in both chili and brinjal. Furthermore, dissipation kinetics of a formulation undertaken under field conditions at four different locations on chili and brinjal suggested that the terminal residues of both bifenthrin and pyriproxyfen were below the maximum residue limits set by European Union in chili and brinjal, respectively, at the time of harvest and that the use of this pesticide formulation is safe.

Fate of Pyriproxyfen in Soils and Plants

Since the 1990s, the insect growth regulator pyriproxyfen has been widely used worldwide as a larvicide in vector control and in agriculture to fight a very large number of pests. Due to its widespread use it is of first importance to know how pyriproxyfen behaves in the terrestrial ecosystems. This was the goal of this work to establish the fate profile of pyriproxyfen in soils and plants. Thus, in soil, pyriproxyfen photodegrades slowly but its aerobic degradation is fast. The insecticide presents a high tendency to adsorb onto soils and it is not subject to leaching into groundwater. On the contrary its two main metabolites (4'-OH-Pyr and PYPAC) show a different fate in soil. When sprayed to plants, pyriproxyfen behaves as a translaminar insecticide. Its half-life in plants ranges from less than one week to about three weeks. The review ends by showing how the fate profile of pyriproxyfen in soils and plants influences the adverse effects of the molecule on non-target organisms.

Soil presence reduces the control effectiveness of a slow-release formulation of pyriproxyfen on Aedes aegypti (Diptera: Culicidae) larvae

OBJECTIVE

To assess the influence of soil on the effectiveness of two new slow-release formulations (floating and non-floating) of pyriproxyfen coextruded with low-density polyethylene.

METHODS

Two slow-release devices were developed using low-density polyethylene, pyriproxyfen as larvicide and calcium carbonate as filler. A factorial design was used to evaluate the effect of soil presence on the performance of each device. Weekly bioassays were performed.

RESULTS

Soil presence affected treatment effectiveness, but this effect was associated with device type. The tablets were effective for nearly 3 months.

CONCLUSION

Treatment effectiveness could be reduced because of the loss of pyriproxyfen by several physico-chemical processes such as adsorption into the soil.

Determination by chromatography and cytotoxotoxic and oxidative effects of pyriproxyfen and pyridalyl

Pyriproxyfen (PPF) is a larvicide, used to combat the proliferation of Aedes aegypti larvae. The objective of this study was to analyze the compounds of pyriproxyfen and pyridalyl (PYL) in a commercial larvicide to analyze the cytotoxic and oxidative effects of PPF and PYL. The toxic potential of PPF and PYL were assessed based on lethal concentration (LC₅₀) in Artemia salina, cytotoxicity based on the mitotic index and the chromosomal alterations in Allium cepa and the oxidative damage in Saccharomyces cerevisiae. The PPF and PYL compounds were identified by HPLC-PDA based on their retention times and spectral data. The wavelengths λ_max (258 nm) and (271 nm) of the UV spectrum of PYL and PPF and the retention times (R_T) (3.38 min) and (4.03 min), respectively. The toxicological potentials of PPF and PYL were significant at concentrations (1, 10, 100 and 1000 ppm), with an LC₅₀ of 48 h (0.5 ppm). PPF and PYL pointed out a cytotoxic effect in A. cepa at all concentrations (0.0001, 0.001, 0.01, 0.1, 1.0, 100 and 1000 ppm), genotoxic effect at concentrations only (0.0001; 0.1; 1; 100 and 1000 ppm), and mutagenic for concentrations (0.1, 100 and 1000 ppm). In relation S. cerevisiae, PPF e PYL prompted oxidative damage at concentrations (100 and 1000 ppm) in all strains (SODWT, Sod1, Sod2, Sod1Sod2, Cat1 and Sod1Cat1). Therefore, the PPF and PYL identificated in commercial larvicide by HPLC-PDA produced cytotoxic and oxidative effects that could cause health and ecosystem risks.

The enantioselective environmental behavior and toxicological effects of pyriproxyfen in soil

We synthesized nine pyriproxyfen (PYR) metabolites and developed a chiral residual analysis method for PYR with its metabolites in five soils using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Soil degradation research showed that higher organic matter content and bigger soil particle size were conducive to the degradation of PYR and metabolites. Metabolite A 4'-OH-PYR was mainly found in five soils. PYR and metabolite A performed enantioselective degradation in soil with half-lives ranging from 2.11 d to 9.69 d and 2.80 d to 13.30 d, respectively. The activity of dehydrogenase, sucrase was inhibited and catalase activity was promoted under the disturbance of PYR. Urease was more sensitive to PYR with uncertain influences. Most soil enzymes were not restored to their initial active state after 120 d. The toxicity of metabolites to earthworms was greater than that of the parent compound PYR. This study provides the basic degradation and toxicity data of chiral pesticide PYR and its main metabolites in soil ecosystem, which is of great significance for guiding safe use and comprehensive evaluation of PYR on environmental risk.

Enantioselective dissipation of pyriproxyfen in soil under fertilizers use

An enantioselective method of pyriproxyfen enantiomers in fertilized soil was established on Lux Cellulose-3 column using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The effects of urea, potassium dihydrogen phosphate, organic fertilizer and compound fertilizer on the dissipation of pyriproxyfen in soil were investigated. Studies have shown that pyriproxyfen had a good linearity in the range of 0.050-7.5 μg/g. The method LODs and LOQs of two enantiomers were 0.0032-0.015 μg/g and 0.050 μg/g, respectively. The recoveries of two enantiomers ranged from 80.61% to 110.86%, intra-day together with inter-day RSDs of 1.38-12.52%. The results indicated that compound fertilizer could promote the dissipation of pyriproxyfen in soil, while the organic fertilizer, potassium dihydrogen phosphate and urea slowed down the dissipation of pyriproxyfen. Enantioselective dissipation of pyriproxyfen enantiomers occurred in blank soil and fertilized soil but performed not obviously. Pyriproxyfen almost not dissipated for 42 d when urea was added. These results revealed that the use of fertilizers would have impacts on the behaviors of this pesticide. The impacts were relatively complex which should be fully considered in future environmental risk evaluation.