Effects of fertilizer on insecticides adsorption and biodegradation in crop soils

Ecological risk assessment of the effects of neonicotinoid insecticides on northern bobwhites (Colinus virginianus) in the South Texas Plains Ecoregion

Neonicotinoid insecticides are among the latest class of insecticides that can have harmful effects on birds. Approximately 30 000 kg of neonicotinoid insecticides are applied annually to 429 100 ha of row-crop fields within the South Texas Plains Ecoregion, Texas, USA. Various studies have demonstrated that treated seeds can be highly toxic to northern bobwhites, with the consumption of only 20 corn seeds causing a fatality. Similarly, other studies have indicated that neonicotinoid insecticides can reduce arthropod populations-a substantial prey base for northern bobwhites, especially during the breeding season-by approximately 60%. Our objective was to conduct an ecological risk assessment of neonicotinoid insecticides' impact on northern bobwhite (Colinus virginianus) populations in the South Texas Plains Ecoregion. We estimated that juvenile and adult northern bobwhites could intake from 7.32 to 27.0 mg/kg/day and from 10.0 to 37.5 mg/kg/day of neonicotinoid insecticides, respectively, which can cause adverse effects on growth, reproductive output, and long-term survival. Our study determined that the application of 30 000 kg of neonicotinoid insecticides annually in the South Texas Plains Ecoregion harms the region's northern bobwhite that are exposed to neonicotinoids. Integr Environ Assess Manag 2022;18:488-499. © 2021 SETAC.

Sorption/Desorption and Kinetics of Atrazine, Chlorfenvinphos, Endosulfan Sulfate and Trifluralin on Agro-Industrial and Composted Organic Wastes

The use of pesticides presents a risk to terrestrial and aquatic ecosystems. For this reason, the development of strategies to prevent and restore pollution is of the greatest interest, including the adsorption to organic matter. The aim of the present study was to investigate the sorption/desorption and kinetics of atrazine, chlorfenvinphos, endosulfan sulfate, and trifluralin onto several raw organic wastes by batch experiments. Three kinetic models were used to fit the obtained sorption kinetics data and two to fit the obtained adsorption isotherm data; both the Freundlich and pseudo-second-order kinetic models described the sorption isotherms well. The desorption study revealed hysteresis in all cases, showing strong, and not completely reversible, adsorption in most cases, with the exception of atrazine-sawdust and chlorfenvinphos-sawdust and chicken manure combinations, for which responses were weak and irreversible. The best kinetic, adsorption and desorption constants were achieved for the hydrophobic pesticides. With respect to sorption-desorption rates, orujillo was found to be the best adsorbent for atrazine, while composted urban solid waste was more suitable for trifluralin and endosulfan sulfate. Sorption constants and simple correlations indicated that, not only the organic matter content, but also the nature of the organic matter itself, and the pesticide and adsorbent properties, determine pesticide sorption-desorption. The use of wastes as efficient and cheap adsorbents for reducing the risk of pesticide pollution is proposed.

Impact of organic manures on the persistence of imidacloprid in the sandy clay loam soil of tropical sugarcane crop ecosystem

Impact of organic manures, viz., composted coir pith, press mud, sugarcane trash, and farmyard manure (FYM) on the persistence of imidacloprid in the sandy clay loam soil of tropical sugarcane crop ecosystem, was studied by employing rapid sample preparation method and reversed phase HPLC. The recoveries of the method employed to determine the residues of imidacloprid in the soil were in the range of 94.5 ± 7.02-97.3 ± 2.94% across the five levels of fortification ranged between 0.005 and 0.5 μg/g. Imidacloprid was observed to persist in the soil manured with FYM and composted coir pith for 30 days with the half-life of 7.62 and 7.0 days, respectively as against 21 days with the half-life of 6.66 days in the non-manurial soil. The comparatively longer persistence of imidacloprid in the FYM and composted coir pith-applied soils was attributed to reduced leaching from the plow layer due to the adsorption of insecticide molecules by the added organic manures.

Decaying Organic Matter Does Not Remove Sublethal Effects of Imidacloprid on Mating in Spalangia endius (Hymenoptera: Pteromalidae), a Parasitoid of Filth Flies

Both the parasitoid wasp Spalangia endius Walker and the insecticide imidacloprid are used to control house flies. A recent study found that negative sublethal effects of imidacloprid on killing flies and on offspring production by this parasitoid wasp are eliminated when females have the opportunity to crawl through decaying matter. An enzyme-linked immunosorbent assay showed that the presence of decaying matter reduces the amount of pesticide on their bodies. This study examined whether this was also true for sublethal effects on mating. S. endius were exposed to a realistic concentration of imidacloprid that induces very low mortality. Then, individual parasitoids were allowed to burrow through decaying organic matter or not, followed by mating tests in the absence of decaying matter. Even after 24 h with the decaying matter, copulation for both males and females that had previously been exposed to imidacloprid was delayed compared with no-pesticide controls. Furthermore, for pesticide-exposed males, subsequently burrowing through media made copulation even more delayed than if they were not exposed to media. For pesticide-exposed females, subsequently burrowing through media neither increased or decreased the negative effect of the pesticide exposure. Together with other studies, these results reinforce that use of S. endius and use of imidacloprid are incompatible, even at much lower than recommended concentration, unless application is sufficiently separated in place and time.

A Neonicotinoid Affects the Mating Behavior of Spalangia endius (Hymenoptera: Pteromalidae), a Biological Control Agent of Filth Flies

Spalangia endius Walker is a parasitoid wasp that is commercially available as a biological control agent for filth fly pests in livestock-rearing operations. Imidacloprid is often used to control these flies. The present study examined the sublethal effect of field-realistic concentrations of imidacloprid on mating behavior, offspring sex ratios, and male preference for virgin females. After exposure to imidacloprid, S. endius females that survived were less likely to mate than control females, which will result in male-biased sex ratios because only mated females can produce daughters. Males did not avoid exposed females, but exposed females were almost always unreceptive. Males that survived exposure to imidacloprid exhibited reduced mating competitiveness against unexposed males. However, if an exposed male mated, his mate's sex ratio and ability to control flies was unaffected. Exposed males were also still able to discriminate against mated, and thus usually unreceptive, females. Together with previous studies, these results suggest that not only does imidacloprid reduce the ability of S. endius females to survive and parasitize hosts, but when an exposed female does survive and parasitize hosts, she is likely to produce just sons, because of her lack of receptivity. More-male-biased populations of S. endius will decrease their efficacy for fly control. Thus, the use of imidacloprid along with this parasitoid may be financially inefficient for pest management.

Dissemination of Imidacloprid Through Dairy Cattle Manure and Its Effect on the Biological Control Agent, Spalangia endius (Hymenoptera: Pteromalidae), and a Filth Fly Host, Musca domestica (Diptera: Muscidae)

Filth flies, including house flies, Musca domestica L., develop in animal manure. Adult house flies often are controlled with pesticides such as imidacloprid. How imidacloprid disseminates and persists after it contaminates manure was measured at a dairy farm. A week after application of imidacloprid via fly bait to cattle manure, a mean of approximately 4 ppm of imidacloprid, and as high as 15 ppm, was quantifiable up to 12 cm from the application site, but not farther. Laboratory experiments addressed the impact of 15 ppm of imidacloprid in manure on egg-to-adult development of house flies and on the biological control ability of a house fly pupal parasitoid, Spalangia endius Walker. In uncontaminated manure, 93% of eggs developed to adults, versus 7% in contaminated manure. In the parasitoid experiment, fly pupae were placed in contaminated or uncontaminated manure with or without S. endius. In the absence of S. endius, nearly 100% of flies emerged, with or without imidacloprid. In the presence of S. endius, only 11% of flies emerged from uncontaminated manure, versus 36% from contaminated manure; and parasitoids emerged from 82% of hosts in uncontaminated manure versus 53% in contaminated manure. These results suggest that realistic concentrations of imidacloprid in filth fly breeding habitat may interfere with house flies developing to the pupal stage, but also with parasitoids locating and utilizing house flies. However, after 1 wk, the effects on parasitoids will be low 12 cm beyond where bait was applied.

Determination of nitenpyram and 6-chloronicotinic acid in environmental samples by ion chromatography coupled with online photochemically induced fluorescence detector

A simple, cost-effective, sensitive, and quick method for the determination of nitenpyram and its metabolite 6-chloronicotinic acid in environmental samples was developed by coupling an ion chromatograph with a fluorescence detector and a post-column photochemical reactor. This developed analytical method involved a rapid sample extraction by modified and miniaturized quick, easy, cheap, effective, rugged, and safe method followed by isocratic ion chromatographic separation of nitenpyram and 6-chloronicotinic acid into an IonPac^™ AS11-HC column protected by IonPac^™ AG11A guard column by running 30 mM NaOH + 10% acetonitrile mobile phase. A homemade post-column photochemical reactor was also integrated with the ion chromatographic system for online transformation of both analytes into their respective highly fluorescent photoproduct in basic media without using an extra pump. The developed method was validated by following SANTE/11945/2015 guidelines on analytical quality control and validation procedures. The method showed a good linear response (r > 0.999), improved limit of detection (0.101-0.132 μg/L), minimum or no matrix effect, excellent recoveries (90.2-100.10%) and relative standard deviations were found to be ≤6.50%.

Degradation of chiral neonicotinoid insecticide cycloxaprid in flooded and anoxic soil

Cycloxaprid (CYC), with two stereogenic centers from oxabridged ring, is a novel potent neonicotinoid insecticide. The investigation of relevant transformation products (TPs) is critical for the risk evaluation of CYC on environment impact and further regulatory decisions. In this study, stereoselective soil metabolism of CYC enantiomers was investigated using isotope labeling techniques. Liquid scintillation counting with LC-MS/MS was used to identify and quantify the major transformation products (TPs) of CYC enantiomers in four various soils under anoxic and flooded condition. Most of CYC had been transformed in four soils at 5d after treatment. Furthermore, CYC was found converted to a range of transformation products, which exhibited soil-specific dynamic changes. Cleavage of the oxabridged seven-member ring, reductive dechlorination in the chloropyridinyl and cleavage of C-N between the chloropyridinylmethyl and imidazalidine ring are the main transformation pathways of CYC. It is presumed that acidic condition may conduce to form the cleavage product of oxabridged seven-member ring. However, abiotic or biotic stereoselective persistence of TPs in all soils was not observed from the experimental data and may be attributed to the unstable oxabridged ring.

A Survey of Imidacloprid Levels in Water Sources Potentially Frequented by Honeybees (Apis mellifera) in the Eastern USA

Imidacloprid, a water-soluble neonicotinoid pesticide used globally in many applications, has been the subject of numerous studies (1) to determine its sublethal effects (5-100 ppb, LD50 ∼200 ppb) on honeybees. This study was undertaken to determine, by ELISA assay, the presence of imidacloprid in water sources potentially frequented by honeybees in urban, suburban, and rural environments across the state of Maryland. Eighteen sites (six samples/site) were chosen which spanned diverse habitats including golf courses, nursery, livestock and crop farms, residential neighborhoods, and cityscapes. Hives were present either at or within 0.5 miles of each site. Imidacloprid was quantifiable in 8 % of the samples at sublethal levels (7-131 ppb). They were not clustered at any one type of site. Results for 13 % of the samples were at the threshold of detection; all others were below the detection limit of the assay (<0.2 ppb).

Enhancing soil sorption capacity of an agricultural soil by addition of three different organic wastes

This study evaluated the ability of three unmodified organic residues (composted sewage sludge, RO1; chicken manure, RO2; and a residue from olive oil production called 'orujillo', RO3) and a soil to sorb six pesticides (atrazine, lindane, alachlor, chlorpyrifos, chlorfenvinphos and endosulfan sulfate) and thereby explored the potential environmental value of these organic residues for mitigating pesticide pollution in agricultural production and removing contaminants from wastewater. Pesticide determination was carried out using gas chromatography coupled with mass spectrometry. Adsorption data were analyzed by the Langmuir and Freundlich adsorption approaches. Experimental results showed that the Freundlich isotherm model best described the adsorption process and that Kf values increased with an increase in organic matter (OM) content of the amended soil. The order of adsorption of pesticides on soils was: chlorpyrifos≥endosulfan sulfate>chlorfenvinphos≥lindane>alachlor≥atrazine. The sorption was greater for the most hydrophobic compounds and lower for the most polar ones, as corroborated by a negative correlation between Kf values and solubility. Sorption increased with an increase in organic matter. Sorption capacity was positively correlated with the organic carbon (OC) content. The organic amendment showing the maximum sorption capacity was RO3 in all cases, except for chlorfenvinphos, in which it was RO2. The order of adsorption capacity of the amendments depended on the pesticide and the organic dosage. In the case of the 10% amendment the order was RO3>RO2>RO1>soil, except for chlorfenvinphos, in which it was RO2>RO3>RO1>soil, and atrazine, where RO2 and RO3 amendments had the same effect on the soil sorption capacity (RO2≥RO3>RO1>soil).

Fate of imidacloprid in soil and plant after application to cotton seeds

This study aimed to investigate the persistence of imidacloprid in soil after application to cotton seeds and to obtain a complete picture on the mass balance of this compound in soil and cotton plants. The study was carried out as a pot culture experiment under laboratory conditions using a Gaucho formulation containing (14)C-labeled imidacloprid. Three treatments of cotton seeds were made in sandy loamy soil: live seeds grown in autoclaved soil, dead seeds put in live soil and live seeds grown in live soil. Results showed that total (14)C recoveries decreased by time ranging 93.8-96.2, 77.1-88.4 and 53.5-62.4% of the applied radioactivity at 7, 14, and 21 d after application, respectively. The reduction in the extracted (14)C from soil coincided with the increase of non-extracted ones. Levels of bound (14)C was always less in autoclaved soil than in live ones. Results revealed also that only 1.8-6.8% of the applied (14)C was taken up by the plants and fluctuated within the test period. (14)C levels were higher in plants grown in autoclaved soil than those in live ones and the radioactivity tended to accumulate on the edges of cotton leaves. Most of the radioactivity in the soil extracts was identified as unchanged (14)C-imidacloprid.

Time-dependent sorption of imidacloprid in two different soils

Time-dependent sorption of imidacloprid [1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine] was investigated with two German soils (sandy loam and silt loam). Soil batches containing the active ingredient (0.33 mg/kg) were incubated for 100 days. After selected aging periods, imidacloprid desorbed by 0.01 M CaCl(2) (soluble phase) and by organic solvents (methanol and acetonitrile) and reflux extraction with acidified methanol (sorbed phase) was determined. Calculated sorption coefficients K(d) and K(oc) increased by a factor of 3.2-3.8 during 100 days of aging. Additionally, the time-dependent sorption was verified by a column leaching experiment with the aged soil. The amount of imidacloprid in column eluates (0.01 M CaCl(2)) decreased compared to total recovered by a factor of approximately 2. Sorption of imidacloprid thus increased with residence time in soil, making it more resistant to leaching. These results are further information to explain the low leaching potential of imidacloprid in the field, despite its high water solubility.