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Oxamyl is a carbamate insecticide used to control a broad spectrum of insects. It can also affect non-targeted organisms when applied incorrectly. The world food production depends partially on honeybee pollination abilities and therefore it is directly linked to the health of bees. The success of the colony development depends, among other factors, on the health of the larvae. The first 6 days are crucial for their development. In this stage, the worker larvae grow exponentially and may be exposed to xenobiotics via their diet. In this study, we investigated the effect of oxamyl on honeybee larvae (Apis mellifera) by monitoring the changes in their antioxidant enzyme system. The activities of superoxide dismutase, catalase and glutathione-S-transferase were determined in the homogenates of in vitro reared honeybee larvae after their single dietary exposure to oxamyl at doses of 1.25, 2.5, 5, 10 and 20 µg a.i./larva (a. i.—active ingredient). The doses of oxamyl did not cause statistically significant changes in the activities of the enzymes. Even a slight activation of these enzymes protected the larvae from the adverse effects of the reactive oxygen species (ROS). Marked changes in both the enzyme activity and the content of lipid peroxidation products were observed at the oxamyl dose of 10 µg a. i./larva. This fact may indicate a potential oxidative damage to the larvae. These results allowed us to assume that the toxic effects of oxamyl involves not only the inhibition of acetylcholine esterase but is also associated with ROS production.

Abstract Agriculture sector of Saudi Arabia is growing swiftly and tomato is an important crop cultivated mostly under green houses. Unfortunately, it is facing severe infestation due to divers mite species. Present study, relates to evaluation of toxicity of oxamyl against two phytophagous mites; Aculops lycopersici and Tetranychus urticae, isolated from tomato plants suffering from infestation. Simultaneous effect of oxamyl on two predatory mites; Neosiulus cucumeris and Euseius scutalis, was also evaluated. Three concentrations of oxamyl; half of the recommended dose (HRD), recommended dose (RD) and double recommended dose (DRD), were used against each mite specie to observe mortality within seven days as compared to the control. Significant mortality of 97.91% and 93.92% was observed in A. lycopersici and T. urticae, respectively at RD. In case of predatory mites; N. cucumeris and E. scutalis, mortality was 60.61% and 64.48%, respectively, under same conditions. Mortality of mites observed at HRD was insignificant and there was negligible increase in mortality at DRD. Oxamyl being less toxic to predatory mites and significantly mortal to phytophagous mites is recommended as a tool to as a tool to achieve biological control parallel to pesticidal effect. Resumo O setor agrícola da Arábia Saudita está crescendo rapidamente e o tomate é uma cultura importante cultivada principalmente em estufas. Infelizmente, está enfrentando uma infestação severa devido a diversas espécies de ácaros. O presente estudo refere-se à avaliação da toxicidade do oxamil contra dois ácaros fitófagos; Aculops lycopersici e Tetranychus urticae, isolados de tomateiros infestados. Efeito simultâneo de oxamil em dois ácaros predadores; Neosiulus cucumeris e Euseius scutalis, também foi avaliado. Três concentrações de oxamil; metade da dose recomendada (HRD), dose recomendada (RD) e dose dupla recomendada (DRD), foram usados contra cada espécie de ácaro para observar a mortalidade em sete dias em comparação com o controle. Mortalidade significativa de 97,91% e 93,92% foi observada em A. lycopersici e T. urticae, respectivamente no RD. No caso de ácaros predadores; N. cucumeris e E. scutalis, a mortalidade foi de 60,61% e 64,48%, respectivamente, nas mesmas condições. A mortalidade de ácaros observada no HRD foi insignificante e houve um aumento insignificante na mortalidade no DRD. Oxamil sendo menos tóxico para ácaros predadores e significativamente mortal para ácaros fitófagos é recomendado como ferramenta para alcançar o controle biológico paralelo ao efeito pesticida.

Pesticide use has increased in the Lake Tana sub-basin due to increased agricultural activity, potentially endangering nontargeted organisms. To assess its potential impact on fish health and fish-consuming human populations, pesticide concentrations in the fillet and liver tissue of three fish species, namely Labeobarbus megastoma , Labeobarbus tsanensis , and Oreochromis niloticus , were investigated in Lake Tana. Fish samples were taken from the lake near the rivers of Ribb and Gumara, which flow through agricultural areas where considerable amounts of pesticides have been applied. A total of 96 fish samples were collected. Liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) revealed the presence of ten pesticides. Pyrimethanil was frequently detected in 96% of liver and 65% of fillet samples at a median concentration of 33.9 µg kg −1 and 19.7 µg kg −1 , respectively. The highest concentration of pyrimethanil was found in L. megastoma (1850.0 µg kg −1 ). Labeobarbus megastoma also had the highest concentration of oxamyl (507.0 µg kg −1 ) and flazasulfuron (60.1 µg kg −1 ) detected in the liver tissue. The highest concentration of carbaryl (56.5 µg kg −1 ) was found in the liver tissue of O. niloticus . Fish tissue samples from the two study sites contained pyrimethanil, oxamyl, carbaryl, and flazasulfuron. Only pyrimethanil showed a statistically significant difference between the two sites and the species L. megastoma and L. tsanensis . The amounts of pesticides found in the fish species pose no direct risk to the health of fish consumer human population. However, the results show that the lake ecosystem needs immediate attention and regular monitoring of the rising pesticide usage in the lake watershed.

Plant-parasitic nematodes (PPNs) are highly damaging pests responsible for heavy losses in worldwide productivity in a significant number of important plant crops. Common pest management strategies rely on the use of synthetic chemical nematicides, which have led to serious concerns regarding their impacts on human health and the environment. Plant natural products, or phytochemicals, can provide a good source of agents for sustainable control of PPNs, due to their intrinsic characteristics such as higher biodegradability, generally low toxicity for mammals, and lower bioaccumulation in the environment. In this work, the nematicidal activity of 39 phytochemicals was determined against the root-lesion nematode (RLN) Pratylenchus penetrans using standard direct and indirect contact methodologies. Overall, the RLN was tolerant to the tested phytochemicals at the highest concentration, 2 mg/mL, seldom reaching full mortality. However, high activities were obtained for benzaldehyde, carvacrol, 3-octanol, and thymol, in comparison to other phytochemicals or the synthetic nematicide oxamyl. These phytochemicals were seen to damage nematode internal tissues but not its cuticle shape. Also, the environmental and (eco)toxicological parameters reported for these compounds suggest lower toxicity and higher safety of use than oxamyl. These compounds appear to be good candidates for the development of biopesticides for a more sustainable pest management strategy.

A monitoring study was carried out in two micro-catchments in the Reventazón basin, in Northern Cartago, Costa Rica; pesticide occurrence and water quality were analyzed. Twelve pesticides were detected, fve insecticides (chlorpyrifos, carbofuran, cypermethrin, imidacloprid, and oxamyl), four fungicides (carbendazim, imazalil, metalaxyl, and thiabendazole), and three herbicides (diuron, linuron, and terbutryn); eight of them presented risk quotients RQ >1, which implies a high risk for the environment. The water quality evaluation included fourteen physicochemical and microbiological parameters, out of which thermotolerant coliforms, nitrate, and total phosphorus exceeded a selected threshold value in every sample. Five metals were also included in the evaluation, Pb was the most frequent, followed by few detections of Cd, Cu, and Cr. Four water quality indexes (WQIs) were applied, two of them, the CCME WQI, based on physicochemical parameters, and the BMWP-CR WQI, based on benthic macroinvertebrate recount adapted to Costa Rican species, categorized all the sampling points as “bad” and “very bad” quality. This work of monitoring is important in the Latin American region, where there is a lack of information for regulation improvement and management decisions. These results showed poor management of the micro-catchments in this agricultural rural area.

Surface-enhanced Raman spectroscopy (SERS) with cysteamine modified silver-coated gold nanoparticles (Au@Ag-CysNPs) was presented for fast screening of oxamyl and thiacloprid in liquid samples of milk. Concentrations at different levels were detected ranging from 0.5 to 10 ppm by choosing 500–1600 cm −1 spectral range. A strongest Raman peak at 679 cm −1 was ascribed to oxamyl, whereas a band at 1095 cm −1 was associated with thiacloprid in milk samples. The morphology and average size of core-shell nanoparticles (Au@AgNPs) and Au@Ag-CysNPs were acquired by High-resolution transition electron microscopy images and dynamic light scattering. Images showed that Au@AgNPs which had a core size of 28 nm and a shell of 6 nm thickness was modified with 6 nm cysteamine hydrochloride successfully. High coefficient of determination (R 2 ) values of 0.9968 and 0.9875 was calculated for oxamyl and thiacloprid with the limits of detection of 0.031 ppm and 0.023 ppm, respectively. The current novel nanoparticle was easy to prepare and was suitable to serve as a sensitive substrate for SERS detection applications, which could be employed for assessing other accidental contaminants in other food matrices in future studies.

Many regulatory agencies establish maximum residue levels (MRLs) for pesticides in livestock products to protect human health. However, the relationships between pesticide MRLs across different products from the same livestock animal and their impact on animal health remain unknown. To address these questions, we developed compatibility, livestock-health, and human-health mechanisms within a regulation-oriented framework. For the compatibility mechanism, which aims to prevent inconsistencies in the MRLs of pesticides set for raw livestock products, we simulated uncertainty intervals for the suggested MRL ratios in raw products from cattle and sheep. For the livestock and human-health mechanisms, we introduced pesticide-specific elimination-equivalent (PSEE) exposure slopes to evaluate animal exposure risks, based on the legal limits of pesticides. Simulation results find that the median suggested MRL ratio of bovine meat (with ~ 20% fat content) to liver (with ~ 3.6% fat content) was 4.90, while the median ratio of liver to kidney was 1.18, indicating that the ratios were determined by the log K OW of the pesticides and the fat content of livestock products. The compatible intervals for DDT's suggested MRL ratios were [3.80, 6.42] for meat/liver and [4.51, 7.62] for meat/kidney. The calculated PSEE exposure slopes reveal that, in general, lipophobic pesticides have steeper PSEE exposure slopes, meaning higher exposure is required to reach the default residue level. For example, assuming a reservation coefficient (ζ) of 1.0, the PSEE exposure slopes of oxamyl (log K OW  = − 0.47) are 0.12 and 0.16 kg kg⁻ 1 d⁻ 1 for bovine milk and liver, respectively, while DDT (log K OW  = 6.91) shows values of 0.066 and 0.064 kg kg⁻ 1 d⁻ 1 . These findings provide a new perspective for improving the comprehensive regulatory process.

Potato cyst nematodes (PCNs) pose a great challenge for potato cultivation throughout the world. Being a rather difficult parasite due to a number of its physiological features, specifically a long-term viability of the eggs, PCN causes drastic damage to worldwide agriculture. Development of long-acting preparations deposited with nematicidal ingredients could be a novel prospective approach to PCNs management. In this study, composite granules based on polycaprolactone and montmorillonite (PCL/MMT) (100:0; 90:10; 75:25; 50:50) were studied as carriers for oxamyl nematicide. It was shown that the obtained granules are able to postpone the hydrolysis of oxamyl from 17 to 27 days and facilitate its gradual release. The maximum release of oxamyl in water was noted for PCL/MMT 50% granules and amounted to 70.3 µg/ml on day 14. Meanwhile, oxamyl release in soil had relatively the same trend for all the granules with the most release in the first 20 days. Kinetic models demonstrated that for all PCL/MMT granules the release was due to diffusion mechanism. The nematicidal effect of PCL/MMT 50% granules with oxamyl against G. rostochiensis has been demonstrated on potato variety \"Krasnoyarskiy ranniy\".

Root-knot nematodes (Meloidogyne spp.; RKNs) are among the most destructive soil-borne pathogens affecting tomato production. Recently, aggressive species such as M. enterolobii, M. floridensis, and M. haplanaria have been reported in several tomato fields across the southern United States. Host resistance in tomato, effective against commonly prevalent M. incognita, is ineffective against these emerging species, making chemical nematicides the primary management approach. However, studies on the efficacy of chemical nematicides on these emerging RKN species remain limited. This study evaluated the efficacy of four non-fumigant nematicides—fluazaindolizine, fluensulfone, fluopyram, and oxamyl—on the reproduction of these emerging species and M. incognita. Fluensulfone consistently suppressed nematode reproduction by over 90.0% across all species. Fluopyram reduced reproduction by over 50.0% in most species but was less effective against M. enterolobii, with suppression of only 24.3%. Similarly, fluazaindolizine suppressed egg counts by more than 50.0% across all species except M. enterolobii, where it suppressed only 41.1%. Oxamyl suppressed egg counts in M. floridensis and M. incognita by more than 50.0%, but reductions in M. enterolobii and M. haplanaria were lower at 23.2% and 38.7%, respectively. These results highlight species-specific differences in nematicide efficacy and provide a crucial baseline for future research for the management of specific RKN species.

Nematicidal activities of 17 phytochemicals belonging to the monoterpene, sesquiterpene, phenylpropene and alkaloid classes were assessed in vitro and in pot experiments under greenhouse conditions. The results showed that, based on LC50 values, monoterpenes and phenylpropenes were more toxic than sesquiterpenes and alkaloids to second-stage juveniles (J2) of Meloidogyne javanica. α-Terpinene (LC50 = 36.22 mg/L) displayed the highest toxicity against juveniles, followed by α-pinene (LC50 = 47.49 mg/L), nerolidol (LC50 = 53.60 mg/L) and eugenol (LC50 = 73.45 mg/L). Furthermore, α-pinene, α-terpinene and nerolidol were highly effective in reducing egg hatching of M. javanica after 7 days of treatment displaying IC50 values of 43.28, 49.26 and 50.39 mg/L, respectively. The three compounds showed nematicidal activity against eggs comparable to a reference nematicide, oxamyl. In pot experiment with eggplant, α-pinene, α-terpinene, eugenol and nerolidol induced remarkable reduction in number of galls, egg-masses and eggs per plant, and number of second stage juveniles in soil at concentration of 500 mg/L. Also, these compounds increased the growth parameters of eggplant compared with infected control. α-Terpinene gave nematode control and plant growth similar to oxamyl. The results suggest that these four compounds could be applied for M. javanica management.