Soil Insecticides Research Articles

Formalin-casein enhances water absorbency of calcium alginate beads and activity of encapsulated Metarhizium brunneum and Saccharomyces cerevisiae

The control of root-feeding wireworms has become more challenging as synthetic soil insecticides have been progressively phased out due to environmental risk concerns. Innovative microbial control alternatives such as the so-called attract-and-kill strategy depend on the rapid and successful development of dried encapsulated microorganisms, which is initiated by rehydration. Casein is a functional additive that is already used in food or pharmaceutical industry due to its water binding capacity. Cross-linked forms such as formalin-casein (FC), exhibit altered network structures. To determine whether FC influences the rehydration of alginate beads in order to increase the efficacy of an attract-and-kill formulation for wireworm pest control, we incorporated either casein or FC in different alginate/starch formulations. We investigated the porous properties of alginate/starch beads and subsequently evaluated the activities of the encapsulated entomopathogenic fungus Metarhizium brunneum and the CO2 producing yeast Saccharomyces cerevisiae. Adding caseins altered the porous structure of beads. FC decreased the bead density from (1.0197 ± 0.0008) g/mL to (1.0144 ± 0.0008) g/mL and the pore diameter by 31%. In contrast to casein, FC enhanced the water absorbency of alginate/starch beads by 40%. Furthermore, incorporating FC quadrupled the spore density on beads containing M. brunneum and S. cerevisiae, and simultaneous venting increased the spore density even by a factor of 18. Moreover, FC increased the total CO2 produced by M. brunneum and S. cerevisiae by 29%. Thus, our findings suggest that rehydration is enhanced by larger capillaries, resulting in an increased water absorption capacity. Our data further suggest that gas exchange is improved by FC. Therefore, our results indicate that FC enhances the fungal activity of both fungi M. brunneum and S. cerevisiae, presumably leading to an enhanced attract-and-kill efficacy for pest control.Graphic abstract

A liquid chromatographic method for determination of acetamiprid and buprofezin residues and their dissipation kinetics in paddy matrices and soil.

The present study was conducted to investigate the residue status of two insecticides (acetamiprid and buprofezin) and their dissipation kinetics in three matrices viz. paddy grain, straw, and soil. The extraction procedure for residues of these two insecticides was executed using acetonitrile solvent. The analytical method was validated, which showed good linearity with the limit of quantification (LOQ) value of 0.01 and 0.02 mg kg-1 for acetamiprid and buprofezin, respectively. The recovery range was 79.67-98.33 % concerning all the matrices in both the insecticides. Acetamiprid (20% SP) and Buprofezin (25% SC) were applied separately in the paddy field in two doses: single dose (recommended dose) and double dose along with untreated control throughout the experiment. Residue analysis of these two insecticides in paddy (grain and straw) and soil was accomplished employing high-performance liquid chromatography (HPLC) with ultraviolet (UV) detector and confirmed by ultra-performance liquid chromatography (UPLC) coupled with mass spectrometry (UPLC-MS/MS). The dissipation data showed that acetamiprid exhibited higher dissipation in comparison with buprofezin. However, their persistence was found slightly higher in soil. The dissipation dynamics in the rice and soil were discussed with biological half-lives of both the insecticides. Consumer risk assessment study was also made considering its fate to the consumers.

Can the botanical azadirachtin replace phased-out soil insecticides in suppressing the soil insect pest Diabrotica virgifera virgifera?

BackgroundDue to recent bans on the use of several soil insecticides and insecticidal seed coatings, soil-dwelling insect pests are increasingly difficult to manage. One example is the western corn rootworm (Diabrotica virgifera virgifera, Coleoptera: Chrysomelidae), a serious root-feeder of maize (Zea mays). We investigated whether the less problematic botanical azadirachtin, widely used against above-ground insects, could become an option for the control of this soil insect pest.MethodsArtificial diet-based bioassays were implemented under standard laboratory conditions to establish dose response curves for the pest larvae. Then, potted-plant experiments were implemented in greenhouse to assess feasibility and efficacy of a novel granular formulation of azadirachtin under more natural conditions and in relation to standard insecticides.ResultsBioassays in three repetitions revealed a 3-day LD50 of 22.3 µg azadirachtin/ml which corresponded to 0.45 µg/neonate of D. v. virgifera and a 5-day LD50 of 19.3 µg/ml or 0.39 µg/first to second instar larva. No sublethal effects were observed. The three greenhouse experiments revealed that the currently proposed standard dose of a granular formulation of 38 g azadirachtin/hectare for in-furrow application at sowing is not enough to control D. v. virgifera or to prevent root damage. At 10× standard-dose total pest control was achieved as well as the prevention of most root damage. This was better than the efficacy achieved by cypermethrin-based granules and comparable to tefluthrin-granules, or thiamethoxam seed coatings. The ED50 for suppressing larval populations were estimated at 92 g azadirachtin/ha, for preventing heavy root damage 52 g/ha and for preventing general root damage 220 g/ha.ConclusionsThere seems clear potential for the development of neem-based botanical soil insecticides for arable crops such as maize. They might become, if doses are increased and more soil insecticides phased out, a promising, safer solution as part of the integrated pest management toolkit against soil insects.

The human and ecological risks of neonicotinoid insecticides in soils of an agricultural zone within the Pearl River Delta, South China

Neonicotinoid insecticides (NIIs) are extensively used worldwide and frequently detected in the environment. The human and ecological risks associated with the occurrence of NIIs in agricultural zones are of high importance. The present study highlights the regional occurrence and human exposure risks of NIIs in agricultural soil within the Pearl River Delta (PRD), South China. Six neonicotinoids, i.e., imidacloprid, clothianidin, acetamiprid, imidaclothiz, dinotefuran, and flonicamid, were measured in 351 soil samples from Zengcheng, a typical agricultural zone. The soil samples were categorized into three groups based on cultivated plants: vegetables, rice, and fruits. At least one of these neonicotinoid insecticides was detected in 95% of the soil samples. The levels of ∑6NII (range (median)) were 0.26–390 (23), 0.26–280 (6.1), and 0.26–120 (5.0) ng g−1 dry weight in soil samples from vegetable farms, rice paddies, and fruit farms, respectively. Neonicotinoids were detected more frequently and at statistically higher concentrations in vegetable farms than in both rice paddies and fruit farms. This is likely ascribed to higher application frequencies of NIIs in vegetable farms due to higher planting frequencies. The hazard index values for human exposure to NIIs in the agricultural soils were all below 1, suggesting negligible non-cancer risks. The current residual levels of NIIs in the soils could however pose sub-lethal or acute effects to non-target terrestrial organisms such as earthworms. The present study suggests that more information is needed regarding NIIs contamination in soils from agricultural regions of South China to ensure that human and ecological risk from exposure to these compounds can be fully addressed.

Wireworms in Florida Sugarcane

Wireworms, the larval stage of a click beetle, often cause severe damage to numerous crops in Florida. At least twelve species of wireworms have been found in southern Florida, but only the corn wireworm, Melanotus communis, is considered to cause significant economic damage to sugarcane. Since M. communis is the important wireworm species, the rest of this document will pertain to this species. Generally, wireworms are a pest of newly planted sugarcane and only rarely a pest in ratoon sugarcane. More studies are needed, but the current information suggests substantial percentages (e.g. 40% or more) of wireworms could be killed by flooding but, in general, the flood duration had to be at least 4 to 5 weeks at water temperatures above 24 °C. Soil insecticides are generally used in newly planted sugarcane for wireworm control. Insecticides are not used for wireworm control in ratoon sugarcane. Pheromone traps are untested in Florida sugarcane for click beetles but have an important function in for both mass trapping and monitoring in other agricultural systems.

Development of a nanobody-based ELISA for the detection of the insecticides cyantraniliprole and chlorantraniliprole in soil and the vegetable bok choy.

Cyantraniliprole and chlorantraniliprole are anthranilic diamide insecticides acting on ryanodine receptors. In this study, two camel-derived nanobodies (Nbs, named C1 and C2) recognizing cyantraniliprole as well as chlorantraniliprole were generated. C1-based enzyme-linked immunosorbent assays (ELISAs) for the detection of the two insecticides were developed. The half-maximum signal inhibition concentrations (IC50) of cyantraniliprole and chlorantraniliprole by ELISA were 1.2 and 1.5ngmL-1, respectively. This assay was employed to detect these two insecticides in soil and vegetables. The average recoveries of cyantraniliprole from both bok choy (Brassica chinensis L.) and soil samples were 90-129%, while those of chlorantraniliprole were in a range of 89-120%. The insecticide residues in soil and bok choy, which were collected from plots sprayed with cyantraniliprole and chlorantraniliprole, were simultaneously detected by the resulting ELISA and a high-performance liquid chromatography (HPLC) method, showing a satisfactory correlation. Higher concentrations of chlorantraniliprole than cyantraniliprole were detected in soil and vegetables, which indicates the longer persistence of chlorantraniliprole in the environment.

Influence of imidacloprid on bacterial community diversity of mango orchard soil assessed through 16S rRNA sequencing-based metagenomic analysis

Imidacloprid, used against mango hopper, is a persistent insecticide in soil. Microbes have the ability to remove toxic pesticides from soil surface. Metagenomic is an approach for understanding the diversity and related metabolic activities in any environmental sample without culturing the microbes. Metagenomic analysis of mango orchard soil was carried out using 16S rRNA gene sequencing to understand the impact of imidacloprid on soil microbial population. In control and imidacloprid applied soil samples, representative sequences clustered were 0.142930 and 0.082320 million, respectively. At the kingdom level, 85 and 88 percent represented to bacteria, 2 and 1 percent to archaea, and 13 and 11 percent to unassigned for control and treated metagenomes, respectively. At phylum level, 16 and 17 percent of OTUs (operational taxonomic units) were assigned with Proteobacteria, while 13 and 11 percent of OTUs were unassigned in control and imidacloprid-treated samples, respectively. The other abundant phyla in both the samples were Planctomycetes, Bacteroidetes, and Actinobacteria. At class level, 9 and 11 percent of OTUs were assigned with Planctomycetia in control as well as imidacloprid-treated samples, respectively. A number of OTUs present in control and imidacloprid applied samples are 31,173 and 21,909, respectively, with 18,018 number of OTUs shared between the two samples. The genus Gemmata totally disappeared in imidacloprid applied soil, while those belonging to class Phycisphaerae, genus Prevotella and species copri were identified in imidacloprid treatment. Bacterial community transformation was evident from this study indicating possible microbial bioremediation of imidacloprid in mango orchard soil.

The Use of Insecticides to Manage the Western Corn Rootworm, Diabrotica virgifera virgifera, LeConte: History, Field-Evolved Resistance, and Associated Mechanisms.

Simple SummaryThe structure of agricultural enterprises in the western United States Corn Belt (large irrigated monocultures, continuous planting of maize, strong aerial pesticide application and livestock industries) has led to a tradition of extensive insecticide use over time to manage the western corn rootworm, Diabrotica virgifera virgifera LeConte (Dvv) a key insect pest of maize. Dvv damages maize roots, which can cause maize plant instability, reduced plant growth, and significant yield loss. Long-term insecticide use has contributed to Dvv becoming resistant to cyclodiene, organophosphate, carbamate, and pyrethroid insecticides since the 1950s. This paper reviews the historical and current use of insecticides in Dvv management programs and Dvv adaptation to insecticide use. Currently, insecticides have a reduced role in Dvv management programs but are still used as complementary tactics with other management approaches. Past history suggests that the probability of selecting for resistance to any future Dvv control technology will be high if it is not used within an integrated pest management framework with other tactics.The western corn rootworm, Diabrotica virgifera virgifera LeConte (Dvv) is a significant insect pest of maize in the United States (U.S.). This paper reviews the history of insecticide use in Dvv management programs, Dvv adaptation to insecticides, i.e., field-evolved resistance and associated mechanisms of resistance, plus the current role of insecticides in the transgenic era. In the western U.S. Corn Belt where continuous maize is commonly grown in large irrigated monocultures, broadcast-applied soil or foliar insecticides have been extensively used over time to manage annual densities of Dvv and other secondary insect pests. This has contributed to the sequential occurrence of Dvv resistance evolution to cyclodiene, organophosphate, carbamate, and pyrethroid insecticides since the 1950s. Mechanisms of resistance are complex, but both oxidative and hydrolytic metabolism contribute to organophosphate, carbamate, and pyrethroid resistance facilitating cross-resistance between insecticide classes. History shows that Dvv insecticide resistance can evolve quickly and may persist in field populations even in the absence of selection. This suggests minimal fitness costs associated with Dvv resistance. In the transgenic era, insecticides function primarily as complementary tools with other Dvv management tactics to manage annual Dvv densities/crop injury and resistance over time.

Interaction of Soil Microbes and Insecticides in Rice-Brinjal Crop Sequence

Results of a study on the interaction of rynaxypyr, fipronil, cartap hydrochloride, carbofuran, phorate and chlorpyriphos with the soil microbial population are reported. The bacterial population in soil was the most susceptible towards insecticides compared to fungi and actinomycetes. Insecticides exerted negative effect on the population of soil microbes, the effect being more prominent up to 14 d after application. The population of microbes started to recover from 21 d after application. Mean reduction in total bacterial population ranged between 0.22 to 45.86 per cent over control. Cartap hydrochloride was relatively more toxic towards the bacterial community. Fungal population was less susceptible to insecticides, their mean reduction ranging from -1.13 to 30.02 per cent over control. Rynaxypyr was relatively more toxic towards fungal population, while carbofuran was the least. The actinomycetes population also showed relatively less susceptibility to insecticides.Carbofuran recorded toxicity towards actinomycetes population (44.27% mean reduction over control). Cartap hydrochloride was relatively less toxic (9.19% mean reduction over control).

Influence of the neonicotinoid insecticide thiamethoxam on soil bacterial community composition and metabolic function

Understanding of neonicotinoid insecticides toxicity on non-target organisms, such as bees, has indirectly promoted their soil treatment use. However, their effect on soil ecosystems haven’t fully understood. Here, based on 16S rRNA high-throughput sequencing and metagenomics, the effects of neonicotinoid insecticide thiamethoxam on bacterial communities and metabolic functions in two types of soils were studied. Thiamethoxam treatment significantly affected soil bacterial abundance, reduced microbial diversity, and changed the bacterial community structure in the short term, and the structure soon returned to a stable state. Soil type and time were important factors affecting bacterial community structure. Some plant growth-promoting rhizosphere bacteria (PGPR) including Actinobacteria were found, and their populations were reduced, while pollutant-degrading bacteria including Firmicutes were also found, and their populations were increased. Based on metagenomics analysis, thiamethoxam treatment insignificantly promoted or inhibited multiple metabolic processes, but gene abundance of some key processes significantly changed. Subtypes of 18 biodegradation genes (BDGs) and 5 pesticide degradation genes (PDGs) were identified. Thiamethoxam treatment significantly increased the abundance of BDGs and PDGs, including cytochrome P450. Potential hosts of P450 degradation genes, including the genus Rhodococcus, were discovered. Conclusions of this study will promote safety evaluation and degradation-related research on neonicotinoid insecticides in soil.

Western corn rootworm abundance, injury to corn, and resistance to Cry3Bb1 in the local landscape of previous problem fields.

Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of corn in the United States. Transgenic corn expressing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is an important tool used to manage rootworm populations. However, field-evolved resistance to Bt threatens this technology. In areas where resistance is present, resistant individuals may travel from one field to a neighboring field, spreading resistance alleles. An important question that remains to be answered is the extent to which greater-than-expected root injury (i.e., >1 node of injury) to Cry3Bb1 corn from western corn rootworm is associated with rootworm abundance, root injury, and levels of resistance in neighboring fields. To address this question, fields with a history of greater-than-expected injury to Cry3Bb1 corn (focal fields) and surrounding fields (< 2.2 km from focal fields) were examined to quantify rootworm abundance, root injury, and resistance to Cry3Bb1 corn. Additionally, use of Bt corn and soil insecticide use for the previous six years were quantified for each field. Resistance to Cry3Bb1 was present in all fields assayed, even though focal fields had grown more Cry3 corn and less non-Bt corn than surrounding fields. This finding implies that some movement of resistance alleles had occurred between focal fields and surrounding fields. Overall, our data suggest that resistance to Cry3Bb1 in the landscape has been influenced by both local rootworm movement and field-level management tactics.

The value of insect management to US maize, soybean and cotton farmers.

Most US maize, soybean and cotton farmers use Bt crops, insecticidal seed treatments, soil-applied insecticides, and foliar sprays to manage insect pests. Given the global economic importance of these crops, we examine farmer benefits of this insecticide use. Using a telephone survey, we document pest management practices and concerns, estimate adoption and farmer perceived values for these practices, and determine factors besides yield and cost that impact adoption and perceived value. Seed-based technologies (Bt seed, seed treatments) dominated insecticide use. Almost 80% of respondents' planted hectares used Bt crops and more than half used seed treatments, while about one-sixth used soil insecticides and one-sixth to one-third used foliar insecticides. Perceived farmer values per treated hectare were greatest for Bt cotton and foliar insecticides in cotton, especially after first bloom. Values for maize and other cotton insecticide uses were greater than for soybean. Aggregating over treated areas, the largest total values for each crop were for seed-based technologies. In addition to yield and cost, farmers showed significant concern for economic risk and human and environmental safety when making pest management decisions. These non-monetary concerns significantly affected the likelihood farmers used these practices and their perceived value. For these crops, seed-based insecticides dominate farmer insecticide use and the value they derive from insecticides. Because seed purchase is months before planting, farmers rely on risk-based integrated pest management to make pest management decisions, weighing both monetary and non-monetary factors when deciding whether the risks are sufficient to justify the use of insecticides. © 2020 Society of Chemical Industry.

Foxtail Millet: A Climate-Resilient Crop Species with Potential to Ensure Food and Agriculture Security Amidst Global Climate Change

Foxtail millet is one among the earliest cultivated and climate-resilient crop species with an immense nutritional profile. They are adapted to grow under a wide range of harsh environmental conditions ranging from high temperature to drought and salinity. It does not demand proper irrigation, artificial soil nutrients or insecticide. But they are incredible with their nutritional contents; almost five to ten times more nutritionally richer than the extensively consumed rice or wheat in terms of micronutrients, fibres and vitamins. It is a staple food crop in the various regions of Asia and Africa. The current COVID-19 pandemic and forthcoming environmental challenges may lead to the instability of agriculture and food security. Therefore, foxtail millet may serve an emissary crop to meet the demand of food supply for humans and cattle as well as rejuvenate other economically important crops against environmental constraints through biotechnological approaches.

Multiresidue procedure to assess the occurrence and dissipation of fungicides and insecticides in vineyard soils from Northwest Spain

The presence of fungicide and insecticide residues in wine has been largely investigated. However, few studies have addressed the persistence of these compounds in vineyard soils. In this research, we investigate the residues of a relevant number of fungicides and insecticides in vineyard soils, obtained in the Northwest of Spain, at the beginning of each agriculture campaign. Moreover, the dissipation of species showing high concentrations were monitored during the non-vegetative period of vines, in order to understand their soil evolution between application campaigns. To this end, a multiresidue analytical procedure based on pressurized liquid extraction (PLE) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) determination was first optimized. Under final working conditions, absolute recoveries in the range from 70 to 130% were achieved for 44 out of 51 selected compounds. The method LOQs remained at the low ng g−1 level (0.2–13 ng g−1) with a linear response range up to 500 ng g−1. Analysis of vineyard soils, collected during a 2-year period, from a geographic area with a high incidence of fungal diseases, demonstrated the presence of relevant concentrations of several fungicides and the insecticide imidacloprid (IMI) in this compartment. Most compounds detected at the end of the application season remained in soil at the beginning of the next year campaign. Among them, six fungicides (dimethomorph, boscalid, myclobutanil, penconazole, pyraclostrobin and pyrimethanil) and IMI showed average dissipation efficiencies below 50%, so they pose a potential to accumulate in this kind of soils.

Effect of toxicity in Folsomia candida by the use of fungicide and insecticide in subtropical soil

Tropical rainforests are among the most endangered biomes on the planet. They have become the new frontiers for capital expansion, both for the production of agricultural commodities and the exploitation of their natural resources. This article seeks to analyze how the command and control system is being practiced on one of such tropical rainforests, namely the Brazilian Amazon. To achieve the objectives set in the research, exploratory/descriptive methods of qualitative and quantitative approach were carried out through field research and literature review on the subject. In addition, we evaluated the publications that best described the “state of the art” of the theme, always aiming at the quality and comprehensiveness of research by bibliometric mining and field survey through questionnaires administered to military police corporations. While examining the environmental protection agencies and law enforcement agencies, both from Union and the states that make up the Legal Amazon, the conclusion was that all of them devote very little material resources to effective forest protection, and that human resources are infinitely smaller than those recommended by other international nature protection organizations. Moreover, the structure in charge of investigating environmental crimes in the states is either poor or non-existent, and distant from the main regions of deforestation and other environmental crimes, something which favors impunity. It is concluded that the lack of structure of command and control bodies in the Amazon threatens the sustainability of the ecosystem, the economy and the society on local, regional, and global levels.

TOXICITY, NATURAL AND INDUCED DEGRADATION OF CHLORPYRIFOS

The increase in demand for agricultural products due to the growing population led to excessive inputs of pesticides in the agriculture field which resulted in contamination of the environmental segments of life i.e. air, water, and soil. Chlorpyrifos is one of the most extensively used broad-spectrum organophosphate insecticides. The usage and broad-spectrum applicability of chlorpyrifos lead to widespread contamination in the environment and serious damage to non-target organisms. Moreover, metabolites of chlorpyrifos i.e. chlorpyrifos-oxon and 3,5,6-trichloro-2-pyridinol are found to be more toxic than its parent compound. This review emphasizes on various toxic effects of chlorpyrifos and its metabolites on living organisms. The efforts put to develop the efficient methods for the degradation of the insecticide in soil and water i.e. photocatalytic, biodegradation, electrochemical and others have been discussed. Analytical techniques used for the study of degraded products and various intermediates formed during degradation under different conditions are summarized. It also includes the general pathway for the degradation of chlorpyrifos. The review will help in the development of tools for degradation and mineralization of organophosphate pesticides by knowing the mechanism of degradation and applicability of the developed process at a large scale.

Comparing Populations of Western Corn Rootworm (Coleoptera: Chrysomelidae) in Regions With and Without a History of Injury to Cry3 Corn.

Transgenic corn expressing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is an important pest management tool. Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a key pest of corn in the midwestern United States that has developed field-evolved resistance to all available Bt traits. The first Bt trait to be commercialized for management of rootworm was Cry3Bb1 in 2003, and field-evolved resistance appeared in 2009. In this study, we examined fields in counties where greater-than-expected injury to Cry3 (Cry3Bb1 or mCry3A) corn roots (>1 node) had previously been reported (problem counties) and counties where injury had not been reported (non-problem counties). Four to eight fields were sampled per county in 2015, 2016, and 2017 to quantify rootworm abundance, root injury, Cry3Bb1resistance, and rootworm management strategies. Rootworm abundance, root injury, and resistance to Cry3Bb1 did not differ between county types. Management tactics differed between county types, with problem counties growing more corn, using more soil insecticide, and growing more Cry34/35Ab1 corn. Additionally, a comparison of root injury to Bt and non-Bt corn within fields indicated that farmers derived an economic benefit from planting Bt corn to manage corn rootworm. Our results suggest that rootworm populations are similar between problem and non-problem counties in Iowa due to similar levels of selection pressure on Cry3 corn, but problem county fields have applied more management tactics due to previous rootworm issues in the area.

Fate of selected neonicotinoid insecticides in soil–water systems: Current state of the art and knowledge gaps

The occurrence of emerging contaminants, such as: personal care products, medicines, pharmaceuticals, pesticides, and their transformation products in the environment is of concern for human health and aquatic ecosystems due to their high persistence, toxicity and potential to bioaccumulation. Among pesticides, the main attention and thus our focus is on neonicotinoids: acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam, which are widely used classes of insecticides in agriculture. Determining the associated risk to humans and ecosystems from neonicotinoid insecticides requires detailed understanding of their fate and transport in the environment which is complex and includes diverse pathways and processes depending on environmental compartments in which they occur. This paper critically reviews the current state of the art about processes, parameters and phenomena influencing the fate of neonicotinoid insecticides in soil-water systems (i.e. soil and groundwater), and reveals existing knowledge gaps. Sorption, biodegradation, chemical transformations of neonicotinoid insecticides in the soil and leaching to the groundwater, as well as groundwater/surface water interactions are highlighted, as they determine their further migration from sources, through soils to groundwater systems and then to other environmental compartments posing ecological and human risks. A number of key knowledge gaps in fate of neonicotinoid insecticides in soil-water systems are identified, that concern mostly processes and pathways occurring in the groundwater, and require further research to assess the associated risk to humans and ecosystems.

Effects on soil microbial community after exposure to neonicotinoid insecticides thiamethoxam and dinotefuran

The wide application of neonicotinoid insecticides in soil may affect soil microbial community, yet the information is limited. This study first reports the effects of thiamethoxam and dinotefuranon on soil microbial community. Soil from a forest land was collected and spiked with different nominal levels (0.02 mg kg−1, 0.2 mg kg−1 and 2.0 mg kg−1) of thiamethoxam and dinotefuran, respectively, and cultivated for 112 days. During the study, concentrations of the two neonicotinoids and their potential degradation products were monitored by LC-MS/MS. At day 112, the soils were analyzed for genetic profile by high-throughput sequencing and carbon metabolic profile by Biolog-ECO plate. The results showed that thiamethoxam and dinotefuran were both attenuated during the study with rate constants being 0.008–0.017 d−1 and 0.024–0.032 d−1, respectively, and biodegradation played an important role. As compared to the blank control, the exposure to the studied two neonicotinoids changed the microbial community, and the changes were influenced by both the type of neonicotinoid and the level of exposure. As compared to the blank control, the relative abundances of phyla Gemmatimonadetes and OD1 decreased under most exposed conditions, while the relative abundances of Chloroflexi and Nitrospirae increased under most exposed conditions. The community transition changed the functional potential, particularly carbon metabolism (mostly decreased) and nitrogen metabolism (mostly increased). As compared to the blank control, the utilization of total 31 carbon sources (including six categories) was increased under low exposure to thiamethoxam, but was decreased under all other exposed conditions. Low exposure to dinotefuran stimulated the utilization of three categories of carbon sources (amines, carbohydrates and phenolic compounds). Low exposure to both neonicotinoids increased the community diversity, while middle and high exposure to both neonicotinoids decreased the community diversity. These findings provide new insights into the effects of neonicotinoids on microbial community in soil.

The combination of two microextraction methods coupled with gas chromatography for the determination of pyrethroid insecticides in multimedia environmental samples: air, water, soil, urine and blood

AbstractThe salting‐out assisted liquid–liquid extraction (SALLE) combined with dispersive liquid–liquid microextraction based on the solidification of floating organic droplet (DLLME‐SFO) has been first developed as a high preconcentration technique for the extraction of pyrethroid insecticides (PYRs) in multimedia environmental samples, including air, soil, water, human urine, hedgehog serum and plasma. GC‐MS was the separation and determination technique. Under the optimum extraction conditions (sample pH 2; salting‐out solution volume and pH, 2 mL and 3; extraction solution, 300 µL of 1‐undecanol; centrifugation speed and time, 2000 rpm and 15 min) and determination conditions, a linearity range (R2 = 0.9993–0.9999) was obtained in a range of 5–5000 ng/mL. The limits of detection based on a signal‐to‐noise ratio of 3 were between 1.5 and 6.1 ng/mL. The recoveries of the four PYRs ranged from 66 to 122%. The results demonstrated that this SALLE–DLLME‐SFO–GC‐MS method allowed the satisfactory enrichment, purification and determination results of PYRs in multimedia environmental samples.