Doses Of Thiamethoxam Research Articles

Wheat seed quality assessment after thiamethoxam treatment: integrating optical techniques with standard methods

Insecticide treatment of seeds protects against early field pests. Therefore, studies on the physiological and biochemical responses of crops exposed to insecticides are required. Standard (non-optical) tests are used to evaluate the physiological quality of seeds. However, some tests may need to be more sensitive to observe possible differences between the control group and the groups of interest. Optical techniques such as ultra- weak photon emission and Fourier transform infrared spectroscopy have been discovered to aid standard tests. The effects of different doses of Thiamethoxam were evaluated on wheat seeds from the cultivar FPS Certero. Samples were divided into five groups: control and treated with 75, 150, 225, and 300 mL of Thiamethoxam for each 100 kg of seeds. The ultra-weak photon emission results showed that it was possible to classify the treatment doses through the intensity of photon emissions. The Fourier transform infrared spectroscopy analyses can be used for biological analysis but are unrelated to Thiamethoxam seed treatment. Considering the findings, optical techniques can be used as an additional tool for assessing the physiological quality of seeds.

Acute toxicity of the fungicide captan to honey bees and mixed evidence for synergism with the insecticide thiamethoxam

Honey bees are commonly co-exposed to pesticides during crop pollination, including the fungicide captan and neonicotinoid insecticide thiamethoxam. We assessed the impact of exposure to these two pesticides individually and in combination, at a range of field-realistic doses. In laboratory assays, mortality of larvae treated with captan was 80–90% greater than controls, dose-independent, and similar to mortality from the lowest dose of thiamethoxam. There was evidence of synergism (i.e., a non-additive response) from captan-thiamethoxam co-exposure at the highest dose of thiamethoxam, but not at lower doses. In the field, we exposed whole colonies to the lowest doses used in the laboratory. Exposure to captan and thiamethoxam individually and in combination resulted in minimal impacts on population growth or colony mortality, and there was no evidence of synergism or antagonism. These results suggest captan and thiamethoxam are each acutely toxic to immature honey bees, but whole colonies can potentially compensate for detrimental effects, at least at the low doses used in our field trial, or that methodological differences of the field experiment impacted results (e.g., dilution of treatments with natural pollen). If compensation occurred, further work is needed to assess how it occurred, potentially via increased queen egg laying, and whether short-term compensation leads to long-term costs. Further work is also needed for other crop pollinators that lack the social detoxification capabilities of honey bee colonies and may be less resilient to pesticides.

The interaction of nicotinic acetylcholine receptor subunits Ldα3, Ldα8 and Ldβ1 with neonicotinoids in Colorado potato beetle, Leptinotarsa decemlineata

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an extremely destructive notifiable quarantine pest. Over the last two decades, neonicotinoid insecticides, particularly thiamethoxam and imidacloprid, have been used to control it in Xinjiang, and local field populations have developed different levels of resistance in consequence. However, the contributions of nicotinic acetylcholine receptors (nAChRs) to neonicotinoid resistance are currently poorly understood in CPB. Previous studies have shown that nAChRα1, α3, α8 and β1 are major target subunits for neonicotinoids in some model and important agricultural insects including nAChRα1 subunit of L. decemlineata (Ldα1). In this study, the expression levels of Ldα3, Ldα8 and Ldβ1 following 72 h of treatments with median lethal doses of thiamethoxam and imidacloprid were compared using real-time quantitative PCR. These genes were then individually and simultaneously knocked down with Ldα1 by RNA interference (RNAi) using a double-stranded RNA (dsRNA) feeding method for six days to explore their roles in CPB susceptibility to imidacloprid and thiamethoxam. The results showed that the expressions of Ldα3, Ldα8 and Ldβ1 were significantly decreased by 36.99–74.89% after thiamethoxam and imidacloprid treatments, compared with the control. The significant downregulation of the target genes resulting from RNAi significantly reduced the mortality of adults exposed to thiamethoxam and imidacloprid by 34.53% –56.44% and 28.78%–43.93%, respectively. Furthermore, the adult survival rates were not affected by every dsRNA-feeding treatment, while the body weight of the test adults significantly deceased after four and six days of individual gene RNAi. This study showed that Ldα3, Ldα8 and Ldβ1 are down-regulated by thiamethoxam and imidacloprid and play important roles in the tolerance of CPB to neonicotinoids.

Effects of thiamethoxam on brain structure of Bombus terrestris (Hymenoptera: Apidae) workers

Neonicotinoids are the most widely used pesticide compared to other major insecticide classes known worldwide and have the fastest growing market share. Many studies showed that neonicotinoid pesticides harm honeybee learning and farming activities, negatively affect colony adaptation and reduce pollination abilities. Bumblebees are heavily preferred species all over the world in order to ensure pollination in plant production. In this study, sublethal effects of the neonicotinoid insecticide thiamethoxam on the brain of Bombus terrestris workers were analyzed. Suspensions (1/1000, 1/100, 1/10) of the maximum recommended dose of thiamethoxam were applied to the workers. 48 h after spraying, morphological effects on the brains of workers were studied. According to area measurements of ICC's of Kenyon cells, there was a significant difference between 1/10 dose and all groups. On the other hand, areas of INC's of Kenyon cells showed a significant difference between the control group and all dose groups. Neuropil disorganization in the calyces increased gradually and differed significantly between the groups and was mostly detected at the highest dose (1/10). Apart from optic lobes, pycnotic nuclei were also observed in the middle region of calyces of mushroom bodies in the high dose group. Also, the width of the lamina, medulla and lobula parts of the optic lobes of each group and the areas of the antennal lobes were measured and significant differences were determined between the groups. The results of the study revealed that sublethal doses of thiamethoxam caused some negative impacts on brain morphology of B. terrestris workers.

Sublethal effects of thiamethoxam on immune system cells in the workers of Bombus terrestris (Hymenoptera: Apidae).

Neonicotinoids harm especially bumblebees and other species in agricultural areas all over the world. The toxic effect of thiamethoxam from the neonicotinoid group has been little studied especially on bees. This research aimed to evaluate the effects of thiamethoxam on the immune system cells of Bombus terrestris workers. Different ratios of 1/1000, 1/100 and 1/10 of the recommended maximum application dose of thiamethoxam formed the experimental groups. Ten foraging workers were used for each dose and control groups. Contamination was ensured by spraying the prepared suspensions at different ratios to the bees for 20s at a pressure of 1atm. The effects of thiamethoxam on the structures of immune system cells of bumblebees and the amount of these cells were investigated after 48h of exposure. In general, anomalies such as vacuolization, cell membrane irregularities and cell shape changes were detected in prohemocyte, plasmatocyte, granulocyte, spherulocyte and oenocytoid in each dose group. Hemocyte area measurements in all groups were examined comparatively between groups. In general, granulocyte and plasmatocyte sizes were decreased, while spherulocyte and oenocytoid were increased. It was also determined that there was a significant decrease in the amount of hemocytes in the 1 mm3 hemolymph as dose increased. The results of the study revealed that sublethal doses of thiamethoxam negatively affected hemocytes and their amounts of B. terrestris workers.

Field Bioefficacy of Thiamethoxam 25WG over Lipaphis erysimi (Kalt.) in Mustard Eco- System in Open Field Conditions

Mustard aphid, Lipaphis erysimi Kaltenbach is a key pest of rapeseed-mustard and form the basis of crop loss from December to March. Field assessment was done to evaluate the bioefficacy of various doses of thiamethoxam over L. erysimi in mustard agroecosystem. Thiamethoxam 25%WG @ 25g a.i per ha was highly efficient against aphid with high grain yield, cost-effective. The results of former dose was on par with 37.5 g a.i per ha and 50 g a.i per ha after first and second spray with an interval of 10 days under open field environment with > 80% of decline in aphid populations. This was further followed by standard check dimethoate 30 % EC @ 200 g a.i per ha which was on par with thiamethoxam 25%WG@ 12.5 and 16.67 g a.i per ha. The control plot was least efficient and showed huge number of the mustard aphids. To manage the aphid population that reaches ETL, two applications with thiamethoxam 25 WG @ 25 g a.i. per ha at 10 days interval will be quite effective and provide good return.

The Fungus Nosema ceranae and a Sublethal Dose of the Neonicotinoid Insecticide Thiamethoxam Differentially Affected the Health and Immunity of Africanized Honey Bees.

Honey bees (Apis mellifera L.) are affected by different biotic and abiotic stressors, such as the fungus Nosema ceranae and neonicotinoid insecticides, that negatively impact their health. However, most studies so far conducted have focused on the effect of these stressors separately and in European honey bees. Therefore, this study was conducted to analyze the impact of both stressors, singly and in combination, on honey bees of African descent that have demonstrated resistance to parasites and pesticides. Africanized honey bees (AHBs, Apis mellifera scutellata Lepeletier) were inoculated with N. ceranae (1 × 105 spores/bee) and/or chronically exposed for 18 days to a sublethal dose of thiamethoxam (0.025 ng/bee) to evaluate their single and combined effects on food consumption, survivorship, N. ceranae infection, and immunity at the cellular and humoral levels. No significant effects by any of the stressors were found for food consumption. However, thiamethoxam was the main stressor associated to a significant decrease in AHB survivorship, whereas N. ceranae was the main stressor affecting their humoral immune response by upregulating the expression of the gene AmHym-1. Additionally, both stressors, separately and combined, significantly decreased the concentration of haemocytes in the haemolymph of the bees. These findings indicate that N. ceranae and thiamethoxam differentially affect the lifespan and immunity of AHBs and do not seem to have synergistic effects when AHBs are simultaneously exposed to both stressors.

Lethal and Sublethal Dose of Thiamethoxam and Its Effects on the Behavior of a Non-target Social Wasp.

In the last few years, with the increase in agricultural productivity, there has also been an increase in the use of insecticides to combat insects considered pests. However, these chemical compounds end up affecting nontarget insects that also interact with the crops. Studies have shown that social bees are among the insects that are suffering most from the effects of these compounds, resulting in negative ecological and economic impacts, considering that these insects provide pollination services in ecosystems. At the same time, social wasps also interact with plants, including cultivated ones, and perform ecological services similar to those of social bees, so it can be hypothesized that insecticides are also affecting social wasp colonies. Therefore, the purpose of this study was to evaluate contamination and sublethal effects of neonicotinoids on the mobility of the social wasp Protopolybia exigua (Saussure). In the first step, oral exposure experiments were performed to determine lethal and sublethal concentrations. In a second step, the wasps were exposed to sublethal concentrations, in order to evaluate the effects on their mobility. The results demonstrated that this species is more susceptible to exposure to neonicotinoids, compared to several bee species that have so far been studied, but lower than others. Exposure to sublethal concentrations can significantly reduce wasp mobility, which can have short-term consequences both for worker wasps and for the maintenance of their colonies.

Interactions between sublethal doses of thiamethoxam and Nosema ceranae in the honey bee, Apis mellifera

Both Nosema ceranae and insecticides are adversely affecting honey bees. How both factors affect gene expression and honey bee survival are well studied. However, only a few studies dealt with the interactions of the two factors. Here we studied the effects of both, when alone and in combination, on honey bee survival and expression changes of immune and detoxification genes. Newly emerged bees were randomly assigned four different treatments: control bees, bees exposed to thiamethoxam, bees exposed to thiamethoxam and then infected with Nosema, and bees infected with N.ceranae only. When combined with Nosema, thiamethoxam caused a significant reduction in survival from the control, but this reduction is not significantly different from N. ceranae alone. Exposure to thiamethoxam caused significantly increased expressions compared to the control for the genes of abaecin, apidaecin and hymenoptacin, but significantly decreased expression for the defensin gene. When the two factors were combined, the expression patterns were similar to N.ceranae infection alone (apidaecin, defencin and hymenoptaecin), except abaecin, which was increased compared to Nosema infected bees. For detoxification genesCCE8 and CYP315A1, thiamethoxam caused significantly increased gene expression but Nosema caused significantly decreased expression. When combined, the two factors did not show a further increase in Mortality compared to Nosema infection alone. Our study shows a clear combined effect of thiamethoxam and Nosema, but mainly in worker mortality and very little effect on gene expression. This study highlights the importance of observing mortality when studying the effect of insecticide on gene expression.

FIELD EVALUATION OF THIAMETHOXAM 25 WG AGAINST SUCKING PESTS IN OKRA

Two field experiments were conducted to test the efficacy of different dosesof thiamethoxam against okra sucking pests viz., Aphids, Aphis gossypii;leaf hopper, Amrasca biguttela biguttela, and whitefly, Bemisia tabaci andtheir predators in okra agroecosystem. Thiamethoxam 25% WG 25 g a.i./ha(84.71-91.73, 94.12 - 98.11% reduction over control) was highly effectiveagainst aphid, whitefly and leaf hoppers which was on par with 50 g a.i./ha (64.28 - 76.90, 83.70 – 87.92% reduction over control) and 75 g a.i./ha (73.48 - 81.26 and 85.26-92.42% reduction over control) after first andsecond spray, respectively. This was further followed by standard checkthiamethoxam 25% WG @ 25 g a.i./ha (Willoxam®). The plots treated withThiamethoxam 25% WG @ 25, 50 and 75 g a.i. /ha recorded the maximumpopulation of Coccinella spp recorded (4.22-5.10 and 4.33-6.21 nos.) afterfirst and second spray. Thiamethoxam 25% WG @ 75 g a.i./ha treated plotrecorded the maximum yield (8100 kg/ha-1) followed by thiamethoxam25%WG @ 25 and 50 g a.i./ha (7345 and 7690.5 kg/ha-1).

Interactions Between Thiamethoxam and Deformed Wing Virus Can Drastically Impair Flight Behavior of Honey Bees.

Exposure to multiple stress factors is believed to contribute to honey bee colony decline. However, little is known about how co-exposure to stress factors can alter the survival and behavior of free-living honey bees in colony conditions. We therefore studied the potential interaction between a neonicotinoid pesticide, thiamethoxam, and a highly prevalent honey bee pathogen, Deformed wing virus (DWV). For this purpose, tagged bees were exposed to DWV by feeding or injection, and/or to field-relevant doses of thiamethoxam, then left in colonies equipped with optical bee counters to monitor flight activity. DWV loads and the expression of immune genes were quantified. A reduction in vitellogenin expression level was observed in DWV-injected bees and was associated with precocious onset of foraging. Combined exposure to DWV and thiamethoxam did not result in higher DWV loads compared to bees only exposed to DWV, but induced precocious foraging, increased the risk of not returning to the hive after the first flight, and decreased survival when compared to single stress exposures. We therefore provided the first evidence for deleterious interactions between DWV and thiamethoxam in natural conditions.

Chronic High-Dose Neonicotinoid Exposure Decreases Overwinter Survival of Apis mellifera L.

Overwinter colony mortality is an ongoing challenge for North American beekeepers. During winter, honey bee colonies rely on stored honey and beebread, which is frequently contaminated with the neonicotinoid insecticides clothianidin and thiamethoxam. To determine whether neonicotinoid exposure affects overwinter survival of Apis mellifera L., we chronically exposed overwintering field colonies and winter workers in the laboratory to thiamethoxam or clothianidin at different concentrations and monitored survival and feed consumption. We also investigated the sublethal effects of chronic thiamethoxam exposure on colony pathogen load, queen quality, and colony temperature regulation. Under field conditions, high doses of thiamethoxam significantly increased overwinter mortality compared to controls, with field-realistic doses of thiamethoxam showing no significant effect on colony overwinter survival. Under laboratory conditions, chronic neonicotinoid exposure significantly decreased survival of winter workers relative to negative control at all doses tested. Chronic high-dose thiamethoxam exposure was not shown to impact pathogen load or queen quality, and field-realistic concentrations of thiamethoxam did not affect colony temperature homeostasis. Taken together, these results demonstrate that chronic environmental neonicotinoid exposure significantly decreases survival of winter workers in the laboratory, but only chronic high-dose thiamethoxam significantly decreases overwinter survival of colonies in the field.

Impact of sublethal doses of thiamethoxam and Nosema ceranae inoculation on the hepato-nephrocitic system in young Africanized Apis mellifera

We analyzed the morphological changes on the hepato-nephrocitic system (HNS) of Africanized honey bees exposed to thiamethoxam (TMX) and to Nosema ceranae (NOS) in isolation and co-exposure. We also analyzed the relative amount of hemocytes in TMX and/or Nosema-exposed bees. Newly emerged bees were exposed individually per os to TMX, at doses of 0.0856 ng/bee or 0.00856 ng/bee, or to TMX doses and 60,000 spores of N. ceranae per bee. Eight days after the single exposure, the results showed that TMX was extremely deleterious to the HNS at 0.00856 ng/bee, dramatically inducing morphological changes in HNS cells (trophocytes and oenocytes) and increasing hemocyte number. However, the treatment to TMX at 0.00856 ng/bee with additional NOS inoculation provoked the highest critical damage observed on HNS, collapsing the trophocytes, reducing the surface area of oenocytes, and inducing cell death in pericardial cells. Therefore, a sublethal dose of TMX, applied alone or simultaneously with NOS inoculation, triggered the disruption of the HNS and induced progressive damage on worker bees. The results demonstrated an interaction between biotic and abiotic agents in Africanized bees at individual level, whose impact at the colonial level remains to be assessed under field conditions.

Deposition, Distribution, Metabolism, and Reduced Application Dose of Thiamethoxam in a Pepper-Planted Ecosystem.

To decrease the application dose of thiamethoxam (TMX) to control the pepper whitefly (Bemisia tabaci Q), the deposition, dissipation, metabolism, and field efficacy of TMX were investigated in a pepper (Capsicum annuum var. grossum)-planted ecosystem using eight types of nozzles at six concentrations (56.25, 41.25, 26.25, 21.0, 15.75, and 10.5 g a.i./hm2). The initial deposition amount of TMX in the pepper plant first increased and then decreased with increasing application dose. The optimum spray conditions of TMX were found to be a droplet size of 200 μm volume median diameter and a spray volume of 350 L/hm2. Moreover, three metabolites, TMX-dm, clothianidin (CLO), and C5H8O2N3SCl, were detected in the pepper-planted system. The dissipation rate of TMX in the pepper-field ecosystem was leaves > stems > fruits > roots > soils. The results revealed the deposition and fate of TMX in the pepper-field ecosystem, and the application dose could be reduced by 20% based on the minimum recommended dose for controlling pepper whitefly.

Effects of chronic dietary thiamethoxam andprothioconazole exposure on Apis mellifera worker adults and brood.

Chronic exposure of honey bees (Apis mellifera Linnaeus) to the neonicotinoid thiamethoxam and the fungicide prothioconazole is common during foraging in agricultural landscapes. We evaluated the survival and hypopharyngeal gland development of adult worker honey bees, and the survival of the worker brood when chronically exposed to thiamethoxam or thiamethoxam and prothioconazole in combination. We found that 30 days of exposure to 40 μg kg-1 of thiamethoxam significantly (P< 0.001) increased the frequency of death in worker adults by four times relative to solvent control. The worker brood required 23 times higher doses of thiamethoxam (1 mg L-1 or 909 μg kg-1 ) before a significant (P= 0.04), 3.9 times increase in frequency of death was observed relative to solvent control. No additive effects of simultaneous exposure of worker adults or brood to thiamethoxam and prothioconazole were observed. At day 8 and day 12, the hypopharyngeal gland acinar diameter was not significantly different (P> 0.05) between controls and adult workers exposed to thiamethoxam and/or prothioconazole. These results indicate that chronic exposure to field-realistic doses of thiamethoxam and/or prothioconazole are unlikely to affect the survival of adult workers and brood. © 2019 Society of Chemical Industry.

A sublethal dose of thiamethoxam impaired the foraging and discrimination ability of the ant Camponotus japonicas

A sublethal dose of thiamethoxam impaired the foraging and discrimination ability of the ant Camponotus japonicas

Bioactivator on physiological performance of tomato and onion seeds

Vegetable seeds have high commercial value, in the field after sowed seeds were exposed to unfavorable environmental conditions capable of causing reductions in the yield. Thiamethoxam is a bio-activator that may confer tolerance to stresses. In this regard, we aimed to evaluate the influence of thiamethoxam in the physiological performance of four lots of tomato and onion seeds. Seeds were treated with five doses of thiamethoxam, 0.0; 0.2; 0.4; 0.6 and 0.8 ml of product per 1000 seeds. The effects of the seed treatments were evaluated by the assessments of the first count of germination, sprouting test, cold test, accelerated aging and seedling`s emergence in the greenhouse. The experimental design was completely randomized, with four replicates per lot and by species. Data were submitted to analysis of variance and adjusted by orthogonal polynomials, using the adjusting equation based on the significance of F test at 5% probability. The bioactivator provided an increase in germination percentage, the first count of ermination, germination after accelerated aging, cold test and seedling’s emergence for low vigor seed lots. The bioactivator thiamethoxam stimulates the physiological performance of tomato and onion seeds. Doses of 0.5 to 0.6 mL of thiamethoxam per 1000 seeds of tomato and onion correspond to technical maximum efficiency.

Effect of thiamethoxam on foraging activity and mortality of Apis mellifera (L.

Thiamethoxam, a neonicotinoid commonly used for its high selective toxicity to insects, is one of the most commonly used pesticides. However, its effect on beneficial insects such as the honeybee Apis mellifera L is still controversial. As young adult workers perform out-hive duties that are crucial for colony development and survival, the effect of sublethal doses of thiamethoxam on honeybee foraging activity and mortality was assessed. Thiamethoxam had a negative impact on foraging activity and cause mortality of honey bees for a period of three to four days following the spraying in field condition.

Immuno-toxicological effects of different sub-lethal doses of thiamethoxam (TMX) in broiler birds

This project was designed to evaluate the immunotoxicological effects of thiamethoxam (TMX). One-day-old broiler chicks (total of 90) were procured and maintained under standard housing conditions and divided into five groups for 45 days. Group A kept as control. Different doses of TMX were administered through crop tube containing 50, 100, 200, and 400 mg/kg bwt/daily to groups B, C, D, and E, respectively. Immunological parameters including response to sheep red blood cells (SRBCs), avian tuberculin responses and carbon clearance assay were accessed. It was observed that response to SRBCs including IgM and IgG, avian tuberculin and phagocytic responses are adversely affected in a dose-dependent manner with TMX toxicity. Hence it was concluded from the results that TMX is responsible for immunosuppression in broiler chicks even at different sub-lethal doses.

USE OF THIAMETHOXAM, ASSOCIATED WITH INSECT POPULATIONS IN PAPAYA (Carica Papaya Linnaeus) CULTIVATION

Papaya crops areas present phytosanitary problems since neonicotinoid pesticides are currently applied without efficient control methods. It is necessary to study insects behavior associated with this type of crop in response to the use of the neonicotinoid thiamethoxam. In order to know the efficiency of this insecticide, different doses were evaluated for the control of the type of insects referred to below. The study area was the locality of Mata Tambor in Cotaxtla, Veracruz, Mexico. Where a plot of papaya "Maradol" of 2,778 plants ha-1 was established, applying different doses of thiamethoxam during the process: T1) 0 kg/ha; T2) 0.3 kg/ha; T3) 0.4 kg/ha; and T4) 0.6 kg/ha. The variables were: insect population, gross mortality rate and the identification of pests that cause damage to the crop. No significant statistical differences were found in insect populations when applying those different doses. The mortality rate 16 days after applying thiamethoxam was higher in T3 at a dose of 0.4 kg/ha, this response is attributed to the fact that the insecticide achieved a residual effect on the culture. The use of T2 with a dose of 0.3 kg/ha in the crop became effective in pest control, generating a gross mortality rate of 241 individuals. Papaya cultivation can be associated with pests such as Bemisia tabaci, Myzus persicae, Frankliniella occidentalis and Toxotrypana curvicuada, which are the main vectors of virus in the culture.