Rhizosphere Bacteria Help to Compensate for Pesticide-Induced Stress in Plants.

Although exogenous chemicals frequently exhibit a biphasic response in regulating plant growth, characterized by low-dose stimulation and high-dose inhibition, the underlying mechanisms remain elusive. This study demonstrates, for the first time, the compensatory function of rhizosphere microbiota in assisting plants to withstand pesticide stress. It was observed that pak choi plants, in response to foliar-spraying imidacloprid at both low and high doses, could increase the total number of rhizosphere bacteria and enrich numerous beneficial bacteria. These bacteria have capabilities for promoting plant growth and degrading the pesticide, such as Nocardioides, Brevundimonas, and Sphingomonas. The beneficial bacterial communities were recruited by stressed plants through increasing the release of primary metabolites in root exudates, such as amino acids, fatty acids, and lysophosphatidylcholines. At low doses of pesticide application, the microbial compensatory effect overcame pesticide stress, leading to plant growth promotion. However, with high doses of pesticide application, the microbial compensatory effect was insufficient to counteract pesticide stress, resulting in plant growth inhibition. These findings pave the way for designing improved pesticide application strategies and contribute to a better understanding of how rhizosphere microbiota can be used as an eco-friendly approach to mitigate chemical-induced stress in crops.

Effect of ultraviolet on the environmental adaptability of Megalurothrips usitatus (Thysanoptera: Thripidae).

Megalurothrips usitatus Bagnall, an important pest of bean plants, is primarily managed with synthetic insecticides. M. usitatus has developed considerable resistance to various insecticides in multiple cowpea-growing areas in Hainan Province, China, posing challenges to its control in the field. Light control technology is a potentially effective physical control method for M. usitatus. The vision of thrips is highly sensitive to UV light, whereas other biological characteristics remain unknown. Therefore, this study evaluated the effects of ultraviolet light on the biological characteristics of M. usitatus. Results showed that the egg, larval, and pupal stages of M. usitatus were significantly shortened, and the emergence rate (79.59%) and adult survival rate (77.95%) were reduced under a devoid of UV light environment (UV-), compared with the full-spectrum light (control treatment group, CK) (p < 0.05). However, the single spawning quantity and total amount of spawning were significantly higher, and the sex ratio (57%) was the highest under UV- (p < 0.05). Single UV light (UV+) only affected the pupation rate. Also, the antioxidant enzymes, polyphenol oxidase, superoxide dismutase (SOD), and peroxidase activities were significantly and negatively correlated with the progression of generations under UV-, whereas catalase and SOD activities were significantly and positively correlated with the progression of generations under UV+. The UV- light conditions significantly interfered with the behavior selection of M. usitatus. The results of this study showed that the adaptability of M. usitatus populations would be greatly reduced in the absence of ultraviolet light, providing a theoretical basis for the control of M. usitatus populations.

Collection of Data on Pesticides in Maize and Tomato in Africa: Protocol for Africa Pesticide Residue Survey Study.

Pesticide use has grown rapidly in West Africa over the past decades. Regulatory capacity has not kept pace with the rapid proliferation of pesticide products and on-farm use. As a result, health and environmental impacts from the growing use of pesticides, despite their potential importance to food safety, remain largely unmonitored, underreported, and poorly understood by key stakeholders. This study protocol was the document for conducting a pesticide survey study to identify the most critically emerging pesticides across the Continent of Africa. Multiple countries were selected in this study to represent the north, east, south, and west regions of Africa. Two food commodities, maize and tomato, were chosen to monitor the pesticide level for food safety. This study protocol describes the fieldwork and laboratory work per the standards of Good Laboratory Practices (GLP) and ISO-17025 and US EPA 860 Residue Chemistry Guidelines but the survey study performed was not considered as a GLP or ISO 17025 study. This is because many steps were not able to be closely monitored per the GLP requirements. This protocol describes the requirements for a pesticide residue study in food collected from local markets. This protocol describes the test commodities, sampling methods, sample transfer/shipping, storage stability, sample analysis, sample disposal, and documentation and record keeping.

Triple-stage Quadrupole Mass Spectrometer to Determine Ubiquitously Present Per- and Polyfluorinated Alkyl Substances in Drinking Water at Part Per Trillion Levels Using Solid Phase Extraction Approach.

An accurate analytical method was developed to determine selected per- and polyfluorinated alkyl substances (PFAS) at the level of parts per trillion (ppt or ng/L) in drinking water. The method included a concentration step using solid phase extraction (SPE) approach in combination with a liquid chromatography-tandem mass spectrometry system (LC-MS/MS). This method was optimized and validated for the common PFAS contaminants in drinking water. An initial demonstration of capability was established with an acceptable initial calibration, minimum reporting limit (MRL), limit of detection (LOD), initial demonstration of low system background, and initial demonstration of precision (IDP). Isotopically labeled internal standards were used for quantification. Surrogate standards were used to monitor method performance. The current method will help in better understanding of PFAS crisis by providing an efficient measurement of PFAS in water. In this study, the recoveries of four surrogates were between 84 and 113%, and calculated limit of detection (DL) and minimum reporting limits (MRL) were generally 1.0-3.0 and 5-10 ng/L, respectively.

Environmental Hormone Effects and Bioaccumulation of Propiconazole and Difenoconazole in Procypris merus.

Studying the bioaccumulation behavior and toxicity of triazole fungicides is a crucial part of comprehensively evaluating the environmental fate and aquatic toxicity.The current research aimed to reveal the toxic effects of propiconazole and difenoconazole on fish through acute toxicity test, bioaccumulation test and oxidase system activity determination. Here, the propiconazole and difenoconazole concentrations were 11.3 mg/L and 31.2 mg/L for LC50-96 h, both having low toxicity. LC-MS/MS was used to determine the propiconazole and difenoconazole concentrations in five organs (muscle, gill, liver, intestine, and kidney) of Procypris meru. The findings indicate that the bioconcentration coefficients of propiconazole and difenoconazole in grass flower carp were 0.66-27.08 and 2.43-22.72, which belonged to medium enrichment pesticides. The bioconcentration coefficients decreased with the increase of exposure concentration. The two fungicides could induce oxidative stress in fish liver, and the activities of three antioxidant enzymes were inhibited in varying degrees (p < 0.05). The results showed that the content of T3 increased, and T4 decreased when exposed to one-tenth LC50 for 7 days. This study shows that triazole pesticides have bioaccumulation risks on aquatic organisms and clear environmental hormonal effects.

A Preliminary Toxicology Study on Eco-friendly Control Target of Spodoptera frugiperda.

Pyrethroid and indoxacarb are commonly used pesticides to control the fall armyworm (Spodoptera frugiperda) in the crops. There are a series of consequences caused by the use of pyrethroid and indoxacarb pesticides under emergency control, such as pest resistance development, contamination of soil, water, and farm products. This study analyzed the structure and physiological function of the sodium channel in S. frugiperda, which is an important step to elaborate the resistance mechanism of S. frugiperda to indoxacarb and pyrethroid pesticides. According to genetic analysis, the cloned cDNA sequences of sodium channel in S. frugiperda (SfNav) showed the shortest genetic distance with that of the sodium channel in Helicoverpa armigera. Under the induction of three pesticides, the expression of SfNav decreased in the first 12 h and then increased after 24 h. It was concluded that SfNav had a typical structure of the sodium channel of insects and its down-regulated expression can decrease the combination of S. frugiperda with pyrethroid and indoxacarb pesticides. The up-regulated expression of SfNav was conducive to the enhancement of the pesticide resistance.

Controlled Release of Spirotetramat Using Starch-Chitosan-Alginate-Encapsulation.

This study was intended to develop an environment-friendly controlled release system for spirotetramat in an alginate matrix. Four formulations, starch-chitosan-calcium alginate (SCCA), starch-calcium alginate (SCA), chitosan-calcium alginate (CCA), and calcium alginate (CA) complex gel beads, were prepared by the extrusion-exogenous gelation method. The properties of the formulations were studied. The results showed that the release behaviors of the formulations in water could be well described by the logistic model, and the release occurred through Fickian diffusion. Among the four formulations, SCCA showed the highest entrapment efficiency, drug loading and the slowest release rate. Degradation studies revealed that the SCCA formulation exhibited an obvious slower degradation rate of spirotetramat in soils than the commercially available formulation. The estimated half-life of the SCCA formulation was 2.31, 3.25, and 4.51 days in waterloggogenic paddy soil, purplish soil, and montmorillonite, respectively, when the soils were moistened to 60% of its dry weight. This study provided a possible approach to prolong the duration of spirotetramat and to reduce environmental contamination.

Genome Analysis of Cytochrome in Dinotefuran-Treated Apolygus lucorum (Meyer-Dür).

In this study, two CYP genes, CYP395G1 and CYP4EY1, were analyzed in Apolygus lucorum (Hemiptera: Miridae). The expression pattern in different developmental stages of both CYP395G1 and CYP4EY1 revealed that first instar nymphs possessed the highest gene-transcript levels. After 12 h of dinotefuran treatments, the expression levels of CYP395G1 increased by 1.92-fold, while the CYP4EY1 expression decreased. It was observed that the sensitivities of dinotefuran to laboratory strains from F0 to F9 and the mRNA expression levels of CYP395G1 in the F9 dinotefuran selected strain were higher when compared to the control strain. The results suggest that CYP395G1 was possibly a candidate P450 that was involved in dinotefuran detoxification. The dinotefuran resistant strain of A. lucorum was difficult to increase, due to its special molecular structure of dinotefuran compared with other neonicotinoids.

Degradation of chlorpyrifos by an endophytic bacterium of the Sphingomonas genus (strain HJY) isolated from Chinese chives (Allium tuberosum).

The degradation of chlorpyrifos (CP) by an endophytic bacterial strain (HJY) isolated from Chinese chives (Allium tuberosum Rottl. ex Spreng) was investigated. Strain HJY was identified as Sphingomonas sp. based on morphological, physiological, and biochemical tests and a 16S rDNA sequence analysis. Approximately 96% of 20 mg L-1 CP was degraded by strain HJY over 15 days in liquid minimal salts medium (MSM). The CP degradation rate could also be increased by glucose supplementation. The optimal conditions for the removal of 20 mg L-1 CP by strain HJY in MSM were 2% inoculum density, pH 6.0, and 30-35°C. The CP degradation rate constant and half-life were 0.2136 ± 0.0063 d-1 and 3.2451 ± 0.0975 d, respectively, under these conditions, but were raised to 0.7961 ± 0.1925 d-1 and 0.8707 ± 0.3079 d with 1% glucose supplementation. The detection of metabolic products and screening for degrading genes indicated that O,O-diethyl O-3,5,6-trichloropyridinol was the major degradation product from CP, while it was likely that some functional genes were undetected and the mechanism responsible for CP degradation by strain HJY remained unknown. Strain HJY is potentially useful for the reduction of CP residues in Chinese chives and may be used for the in situ phytoremediation of CP.

Safety assessment of chromafenozide residue level with decline study on tomato in Egypt.

The objective of this study is to perform a safety assessment of chromafenozide residue level on tomato at the Egyptian national level. An open field decline study of chromafenozide on tomato was performed. The theoretical maximum daily intake (TMDI) of chromafenozide was calculated for assessing the chronic dietary exposure indicating that the ADI value of chromafenozide (0.27 mg/kg bw/day) was not exceeded. As a result, the safety assessment of chromafenozide residue levels was attained. A validated method of the QuEChERS approach followed by HPLC-DAD analysis was used to determine the chromafenozide residues. The recoveries ranged from 70 to 88% with relative standard deviations ranging from 2.0 to 9.0%. The limit of quantitation was 0.01 mg/kg. The half-life of chromafenozide on tomatoes was 3.5 days.

Behavior of Thiophanate Methyl and Propiconazole in Grape and Mango Fruits Under the Egyptian Field Conditions.

This research aims at determining residues of thiophanate methyl and propiconazole in grape and mango fruits as an indication for their persistence in this environmental compartment. Fruit extracts were analyzed for thiophanate methyl using High Performance Liquid Chromatography and using Gas Chromatography Electron Capture Detector (GC/ECD), respectively. The results indicated that propiconazole had a less environmental impact since propiconazole had shorter residue half-lives which were 1.24 and 1.19 days in grape and mango fruits, respectively, while thiophanate methyl had half-lives of 2.49 and 2.64 days in mango and grape, respectively. The degradation rates of propiconazole in grape and mango fruits did not change significantly and neither did those of thiophanate methyl. According to the maximum residue level, the pre-harvest intervals of propiconazole were set to be 3 and 7 days for grape and mango fruits, respectively, and the pre-harvest intervals for thiophanate methyl were 15 days for both grape and mango fruits. Propiconazole was generally considered to be less hazardous to humans and will leave the environment less altered because of its faster degradation than that of thiophanate methyl.

Residue behaviors of six pesticides during apple juice production and storage.

The residue behaviors of carbendazim, thiamethoxam, imidacloprid, acetamiprid, prochloraz, and difenoconazole during the production and accelerated storage of apple clear and cloudy juice was systemically evaluated. The pesticides were determined by liquid chromatography-mass spectrometry (LC-MS/MS) after each processing step and at different storage times. The results indicated that the different processing steps in the apple clear and cloudy juices production have different effects on the reduction of pesticide residues. The pre-processing steps including washing and pressing reduced the pesticide residues significantly by 36.8 % to 67.9 % and 32.9 % to 89.8 %, respectively, mainly due to the water solubility and log Kow of pesticides. The enzymation step in clear juice production slightly reduced six pesticide residues from 1.9 % to 31.6 %, and the filtration step after clarification and purification decreased the pesticide residues from 14.0 % to 87.5 % with no significance, while prochloraz was not detected. The centrifugation step in cloudy juice production reduced the pesticide residues from 6.3 % to 88.9 %. The pasteurization step in clear and cloudy juice production lowered the pesticide residues slightly on account of the short heating time of 30 s. The accelerated storage of clear and cloudy juices was effective in the reduction of pesticide residue levels. The processing factors (PFs) in the whole process of clear and cloudy juice production were equal to or lower than 0.2, especially for prochloraz and difenoconazole, illustrating that apple juice production could decrease the pesticide residues greatly. The results will provide important references to predict the levels of pesticide residues in apple juice during processing and storage. Meanwhile, the PFs identified in the study could be helpful in the risk assessment of pesticides in apple juice.

Effect of biochar amendment on the bioavailability of pesticide chlorantraniliprole in soil to earthworm.

To evaluate the effect of biochar amendment on the bioavailability of chlorantraniliprole (CAP) in soils with different physico-chemical properties, the uptake of CAP from various soils by earthworms was studied. It was observed that the biochar amendment of the soils affected the sorption of CAP, but the magnitude of the sorption enhancement by biochar amendment among the soils was varied, presumably due to the attenuation of the sorptivity of the biochar when amended in the soil. The amendment with biochars leads to a decrease in the bioavailability of CAP in the soils to earthworms, and more prominent for biochar BC850 amendment. In the soil with a CAP concentration of 10 mg kg(-1), the residue of CAP in the earthworm tissues was found to be 9.65 mg kg(-1), in comparison with that the CAP residue was 4.05 mg kg(-1) in BC450 amended soil and 0.59 mg kg(-1) in BC850, respectively. The degree of bioavailability reduction by same level of biochar amendment was different among soils with different properties. The results demonstrate that the properties of soils are important to performance of biochar in soil.

Analysis of honey bee exposure to multiple pesticide residues in the hive environment.

Since the loss of honeybees in hives could have a greater impact on colony health than those of their foraging bees, it is imperative to know beehives' pesticide exposure via oral ingestion of contaminated in-hive matrices. Here, a 4-year monitoring survey of 64 pesticide residues in pollen, nectar and related beehive matrices (beebread and honey) from China's main honey producing areas was carried out using a modified version of the QuEChERS multi-residue method. The results showed that 93.6% of pollen, 81.5% of nectar, 96.6% of beebread, and 49.3% of honey containing at least one target pesticide were detected either at or above the method detection limits (MDLs), respectively, with up to 19 pesticides found per sample. Carbendazim was the most frequently detected pesticide (present in >85% of the samples), and pyrethroids were also abundant (median concentration = 134.3-279.0 µg/kg). The transfer of pesticides from the environment into the beehive was shown, but the pesticide transference ratio may be affected by complex factors. Although the overall risk to colony health from pesticides appears to be at an acceptable level, the hazard quotient/hazard index (HQ/HI) value revealed that pyrethroids were clearly the most influential contributor, accounting for up to 45% of HI. Collectively, these empirical findings provide further insights into the extent of contamination caused by agricultural pesticide use on honeybee colonies.

Modulation of the tumor microenvironment by intratumoral administration of IMO-2125, a novel TLR9 agonist, for cancer immunotherapy.

The objective of cancer immunotherapy is to prime the host's immune system to recognize and attack malignant tumor cells. IMO­2125, a Toll­like receptor 9 (TLR9) agonist, exhibited potent antitumor effects in the murine syngeneic A20 lymphoma and the CT26 colon carcinoma models. IMO­2125 exhibited superior A20 antitumor activity when injected intratumorally (i.t.) compared with equivalent subcutaneous doses. In mice bearing dual CT26 grafts, the i.t. injection of right flank tumors elicited infiltration of cluster of differentiation (CD)3+ T lymphocytes into tumors, resulting in the regression of injected and uninjected left flank tumors. Depletion of CD8+, but not CD4+, T­cells abrogated the IMO­2125­mediated antitumor response, suggesting that CD8+ lymphocytes are required for the antitumor activity. In mice harboring right flank CT26 and left flank ß­galactosidase (ß­gal)­expressing CT26.CL25 grafts, the i.t. administration of IMO­2125 to the CT26 graft resulted in potent and dose­dependent antitumor activity against the two grafts. Splenic T­cells isolated from these mice responded to AH1 antigen (present in the two tumors) and ß­gal antigen (present only in CT26.CL25) in an interferon γ enzyme­linked immunospot assay, suggesting the clonal expansion of T­cells directed against antigens from the two tumors. Mice with ablated CT26 tumors by previous IMO­2125 treatment rejected re­implanted CT26 tumor cells, but not A20 tumor cells, demonstrating that the initial IMO­2125 treatment created a long­lived tumor­specific immune memory of CT26 antigens. A quantitative increase in CD3+ T lymphocytes in injected A20 tumors and an upregulation of selected checkpoint genes, including indoleamine 2,3­dioxygenase (IDO)­1, IDO­2, programmed cell death protein-1 (PD-1); programmed cell death protein ligand 1 (PD-L1), carcinoembryonic antigen­related cell adhesion molecule 1, tumor necrosis factor receptor superfamily member 4 (OX40), OX40 ligand, T­cell immunoglobulin and mucin­domain­containing 3 protein, lymphocyte­activation gene 3, cytotoxic T­lymphocyte­associated protein 4, were observed following IMO­2125 treatment. IMO­2125 also increased immune checkpoint gene expression in injected and uninjected contralateral CT26 tumors, suggesting that the co­administration of anti­CTLA­4, anti­PD­1 or anti­PD­L1 therapies with IMO­2125 may provide additional therapeutic efficacy.

Effect of Chinese traditional cooking on eight pesticides residue during cowpea processing.

Thermal processing can concentrate residues or convert residues to more toxic metabolites in food. Chinese traditional cooking pays more attention to thermal processing and more vegetables were eaten after thermal processing. In this study, the effect of Chinese traditional cooking (washing, blanching, stir-frying, frying and combined operations) on eight pesticides residues (pyridaben, procymidone, chlorothalonil, difenoconazole, α-cypermethrin, bifenthrin, S-fenvalerate and λ-cyhalothrin) in cowpea which was one of the most important legume crops in China was examined. Result showed washing and blanching could reduce residues with low Kow while stir-frying and frying were more effective to residues with high Kow; stir-frying and frying could concentrate residues with low Kow; the residue levels in oil increased following increasing frying time and frequency especially the residues with high Kow; one metabolite studied in this paper was not detected. Blanching (5 min) followed by stir-frying (3 min) was the most effective combined operation.

Residues and dissipation kinetics of triazole fungicides difenoconazole and propiconazole in wheat and soil in Chinese fields.

An analytical method for simultaneously determining the residues of difenoconazole and propiconazole in wheat straw, wheat grain and soil was developed. Mean recoveries and relative standard deviations in all samples ranged 86.2-101.3% and 3.1-12.1% for propiconazole and difenoconazole. The half-lives of difenoconazole and propiconazole were 3.6-5.5days and 5.1-6.9days in wheat straws, and 4.9-5.8days and 6.1-8.4days in soil, respectively. The residues in wheat grain were found to be <0.01mg/kg, based on the application rate (135g a.i./ha) and the pre-harvest interval (PHI=28days) recommended by the manufacturer. The results suggest that the use of difenoconazole and propiconazole on wheat is considered to be safe under the Good Agricultural Practices (GAP) in the Chinese fields, and the main factors for pesticide residue in crops are application times, rates and pre-harvest intervals.

Changes of field incurred chlorpyrifos and its toxic metabolite residues in rice during food processing from-RAC-to-consumption.

The objectives of this study were to determine the effects of food processing on field incurred residues levels of chlorpyrifos and its metabolite 3,5,6-Trichloro-2-pyridinol (TCP) in rice. The chlorpyrifos and TCP were found to be 1.27 and 0.093 mg kg-1 in straw and 0.41 and 0.073 mg kg-1 in grain, respectively. It is observed that the sunlight for 2 hours does not decrease the chlorpyrifos and TCP residues in grain significantly. Their residues in rice were reduced by up to 50% by hulling. The cooking reduced the chlorpyrifos and TCP in rice to undetectable level (below 0.01 mg kg-1). Processing factors (PFs) of chlorpyrifos and TCP residues in rice during food processing were similar. Various factors have impacts on the fates of chlorpyrifos and TCP residues and the important steps to reduce their residues in rice were hulling and cooking. The results can contribute to assure the consumer of a safe wholesome food supply.

Thiabendazole uptake in shimeji, king oyster, and oyster mushrooms and its persistence in sterile and nonsterile substrates.

Thiabendazole in the substrates incurred from spraying and premixing was translocated to the pileus, stipe, and volva of selected mushrooms. The spraying on the substrates resulted in higher residues of thiabendazole in all three mushrooms than the premixing treatment. For premixing, in the five substrates, half-lives of thiabendazole were found to be 13.6 days for shimeji, 10.0 days for king oyster, 13.7 days for oyster, 19.1 days for sterilized substrate, and 8.4 days for nonsterilized substrate, respectively. For spraying, the longest and shortest half-lives were found to be 19.5 and 8.1 days for the nonsterilized and sterilized substrates, respectively. The residues of thiabendazole in three edible fungi were increased with the incubation days from 3 to 5 to 7. The residues of thiabendazole in king oyster were the highest among the three fungi while those in shimeji and oyster showed similar patterns.