Concentrations Of Emamectin Benzoate Research Articles

Eficácia in vitro do benzoato de emamectina e do glifosato contra parasitos monogenéticos de Colossoma macropomum

ABSTRACT This study investigated the in vitro efficacy of emamectin benzoate and glyphosate against monogeneans from Colossoma macropomum and tolerance of this species to these therapeutic drugs. In vitro assays demonstrated that concentrations of emamectin benzoate (12.5, 16.6, 20.8 and 25.0g/L) and glyphosate (2,000; 3,000; 4,000 and 5,000mg/L) were 100% effective against Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri. The highest concentrations of emamectin benzoate (20.8 and 25.0g/L) were 100% effective after 30 minutes of exposure. For glyphosate, the highest concentrations were the most effective, and 4,000 and 5,000 mg/L immobilized 100% of parasites in 45 minutes and 30 minutes, respectively. Scanning electron microscopy revealed that the parasites exposed to 20.8 and 25.0g/L of emamectin benzoate and 5,000 mg/L of glyphosate presented integument covered with deeper wrinkles. Behavioral changes occurred in C. macropomum exposed to all concentrations of both drugs, were as mortality occurred following exposure to emamectin benzoate and glyphosate at 2.0,12,5 and 25.0g/L and 500, 1,000, 2,000, 3,000, 4,000 and 5,000mg/L, respectively. Low concentrations of emamectin benzoate and of glyphosate were tolerated by C. macropomum, but these concentrations may have not efficacy against infection of monogeneans.

Comparative effectiveness of deltamethrin, imidacloprid and emamectin benzoate alone and in binary blends to control Trogoderma granarium: Effect on macronutrients

Trogoderma granarium Everts (Insecta, Dermestidae) severely attacks a variety of stored commodities, and its control has been achieved by conventional insecticides. However, unplanned use of insecticides leads towards emergence of resistance as well as health and environment damage. Previous studies reported insecticidal efficacy of deltamethrin (DL), emamectin benzoate (EB) and imidacloprid (IM) individually but lacking efficacy of mixtures against T. granarium. The study presented here was aimed at investigating the susceptibility of field collected Mandi Bahaud Din (MBD) population (14 years DL exposure history) and a DL susceptible LAB-S population (not exposed to insecticides since 2001) against DL, EB and IM individually and in binary mixtures (DL:EB, DL:IM and EB:IM) at different ratio (1:1, 1:2, 1:3, 2:1 and 3:1). The MBD strain showed greater susceptibility against IM and EB (LC50 473.09 and 556.4 ppm) respectively, but decreased susceptibility (LC50 808.67 ppm) against DL indicating DL resistance. The LC50 values were 251.62, 307.15 and 369.73 ppm against DL, IM and EB, respectively in LAB-S strain. All binary mixtures exhibited synergistic interactions against MBD strain and EB:IM mixture (3:1) was found the most effective (RTU 3.93) among all the tested combinations. In contrast, EB:IM mixture showed antagonistic interactions (1:1, 1:2, 1:3, 2:1) but synergistic interactions were achieved by increasing EB concentration (3:1, RTU 1.23) in mixture against LAB-S strain. However, DL:EB was more effective (RTU 2.1) against LAB-S strain among all the tested combinations. The toxic effect of LC20 of most effective mixture on macronutrients was also investigated. A significant reduction in contents of trehalose, total protein, soluble protein, total lipids and glycogen while an increase in glucose and free amino acids was observed in both strains in comparison with their respective unexposed control. It is concluded that binary mixture reduces the net quantity of conventional insecticides, thus offering more effective approach to control T. granarium.

Transgenerational Sublethal Effects of Chlorantraniliprole and Emamectin Benzoate on the Development and Reproduction of Spodoptera frugiperda.

Spodoptera frugiperda (J. E. Smith), commonly known as the fall armyworm (FAW), causes significant damage to many different crop species. In this study, age-stage, two-sex life table analysis was used to investigate the effects of sublethal concentrations of emamectin benzoate and chlorantraniliprole on FAW development and reproduction. In the F0 generation, exposure to emamectin benzoate and chlorantraniliprole significantly impacted the duration of FAW, thus prolonging the development duration of each instar, but not the prepupal stage. Furthermore, the weight of FAW pupae was significantly reduced by emamectin benzoate at LC25 and chlorantraniliprole at LC25 in the F0 generation. With respect to fecundity, emamectin benzoate and chlorantraniliprole significantly reduced fecundity in the F0 generation. In the F1 generation, emamectin benzoate at LC10 had no significant effect on the preadult or adult stages, whereas LC25 significantly shortened the preadult period. The preadult and adult stages of FAW exposed to chlorantraniliprole at LC10 and LC25 were significantly prolonged. Furthermore, emamectin benzoate had no significant effect on the pupal weight of the F1 generation. Chlorantraniliprole had no significant effect at LC10, but significant reduced pupal weight occurred at LC25 in the F1 generation. With respect to fecundity, emamectin benzoate significantly reduced fecundity in the F1 generation. Interestingly, chlorantraniliprole significantly increased fecundity in the F1 generation, which could promote population growth and pest resurgence. These findings have important implications for the integrated pest management of FAW and provide a reference for the more effective control of FAW.

Sublethal effects of emamectin benzoate on development, reproduction, and vitellogenin and vitellogenin receptor gene expression in Thrips hawaiiensis (Thysanoptera: Thripidae).

Thrips hawaiiensis (Morgan) (Thysanoptera: Thripidae) is a sap-sucking pest that seriously damages several crops and reduces their economic value. Exposure to low concentrations of insecticides may have a sublethal effect on surviving insects. In order to provide a reference for the rational application of emamectin benzoate, its sublethal effects on the development and reproduction of T. hawaiiensis were evaluated. Pupal development time was significantly shorter in T. hawaiiensis treated with sublethal concentrations of emamectin benzoate (LC10 and LC20) than in control. Female adult longevity and female total longevity were significantly longer following LC20 treatment than in the control and LC10 treatment groups. Nevertheless, male adult longevity and male total longevity were significantly shorter in the LC10 treatment group than in the control and LC20 treatment groups. The sublethal concentration of emamectin benzoate (LC20) significantly shortened the preadult stages and the mean generation. Meanwhile, it significantly increased the finite rate of increase, intrinsic rate of increase, and net reproductive rate. The fecundity was significantly higher after LC20 treatment than after LC10 and control treatments. Compared with the control group, the LC10 and LC20 groups of T. hawaiiensis adults showed a significantly higher expression of the vitellogenin (Vg) and vitellogenin receptor (VgR) genes, which played a key role in increasing their fecundity. These findings suggest that short-term exposure to sublethal concentrations of emamectin benzoate may lead to a resurgence and secondary outbreak of T. hawaiiensis infestation. The results have practical applications for the management of this important and noxious pest.

Distribution of Emamectin Benzoate Granules in Maize Plants by Broadcasting into Maize Leaf Whorls.

Good control effects on fall armyworm (FAW) can be obtained by broadcasting emamectin benzoate (EB) granules into maize leaf whorls. However, the distribution of EB in maize plants is not clear. In this study, EB granules were prepared by the rotating granulation method, and the granules were characterized using a Fourier transform infrared spectrometer. The behavior of EB granules in water was observed using a microscope, and in vitro release of EB from granules was also studied. A method for the determination of EB in maize plants, old leaves, grains, and cobs was established by using ultra-performance liquid chromatography-tandem mass spectrometry. The results showed that EB was loaded in granules successfully, and the granules disintegrated slowly in water, so the release of granules could be regulated using various water contents. The prepared EB granules were qualified and stable. The field experiment showed that the concentration of EB in maize leaf whorls could be maintained above 0.23 mg·kg-1 within 3 days after broadcasting EB granules. This ensured that FAW could be killed in a short time. Then, EB gradually transferred to the old leaves. After 21 days of application, the content of EB in the old leaves was 0.07 mg·kg-1, which has long-time control effects on FAW. The control effects of the three doses of granules against Spodoptera frugiperda were higher than 78% after 14 days of application. At the tested dosage, no phytotoxicity to crops was observed. At harvest, neither the maize grain nor the cobs had EB content. New controlled formulations to S. frugiperda were developed and will be suitable for application in mountainous areas where the lack of water resources is a factor.

Hematological and histopathological impacts of nano-emamectin benzoate against the larvae of the cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) under laboratory conditions

BackgroundInsects withstand foreign substances and infection by expressing robust defense responses, which are mediated by hemocytes, fat body, midgut, and many other tissues. The Egyptian cotton leafworm, Spodoptera littoralis (Boisduval), is a polyphagous pest with considerable economic importance in Egypt and globally. Many control strategies were employed to control this pest. Nowadays, there is a trend to use nanotechnology tools in agricultural practices as they balance minimal concentration and maximum pest control, safe concentration, and reduce the cost of pest control. The present study aimed to evaluate the hematological and histopathological response of S. littoralis larvae post-treatment with sublethal concentrations of emamectin benzoate and its nanoform, besides the silver nanoparticles.ResultsThe results revealed the high toxicity of emamectin benzoate and its nanoform (LC50 values were 0.0524 and 0.023 ppm, respectively). The results also showed that all tested compounds significantly influenced the mean number of laid eggs/female. The emamectin benzoate nanoform (837.3 ± 52.09) was the most efficient compound compared to the control (1999.3 ± 46.5). The hematological responses against the EMB + AgNP were lowered total hemocyte counting (22.41 ± 1.3) compared to the untreated larvae (38.08 ± 0.83). In addition, there were some histopathological changes in the midgut tissues. They were represented as destroying the integrity of the epithelial cells and the ciliated border. The columnar cells began to disintegrate, and the peritrophic membrane became vacuolized. In contrast, the cuticle layers were not affected by various treatments.ConclusionWe can conclude that the employment of emamectin benzoate, either in its original form or as its nanoform, is considered a promising substitute for conventional insecticides. The nanoform of emamectin benzoate proved its high efficiency against the larvae of the cotton leafworm, which may allow the application of this formulation at low concentrations.

Toxicological and Biochemical Description of Synergism of Beauveria bassiana and Emamectin Benzoate against Megalurothrips usitatus (Bagrall)

The prophylactic application of synthetic insecticides to manage Megalurothrips usitatus (Bagrall) has resulted in insecticide resistance and negative impacts upon natural ecosystems. This has driven the need for developing alternative pest control strategies. In the present study, we investigated the synergistic interaction between the entomopathogenic fungus Beauveria bassiana and the insecticide emamectin benzoate on M. usitatus. The results of our research exhibited that higher doses of emamectin benzoate inhibited the germination rate and colony growth of B. bassiana. The percentage of M. usitatus mortality following B. bassiana and emamectin benzoate treatment indicated a dose–mortality effect. All concentrations of emamectin benzoate combined with different concentrations of B. bassiana demonstrated a synergistic effect five days post-treatment. When B. bassiana and emamectin benzoate were applied alone or in combination, antioxidant enzyme activities, including acetylcholinesterase, catalase, superoxide dismutase, and peroxidase, were significantly lower in M. usiatus than in the controls at the end of the experimental period. The findings of our study confirm the synergistic effect of B. bassiana and emamectin benzoate on M. usitatus, as well as the biochemical process that might be involved in the regulation of the synergistic effect.

Evidence of field-evolved resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) to emamectin benzoate in Brazil

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith, 1797), has evolved resistance to several insecticides and Bacillus thuringiensis Berliner (Bt) toxins expressed in transgenic plants worldwide. Recently, we demonstrated a high risk of resistance evolution of a laboratory-selected emamectin benzoate-resistant strain of FAW based on incomplete dominant inheritance. In this study, we presented laboratory studies that established the baseline susceptibility and defined a diagnostic concentration of emamectin benzoate for the FAW performed in 2002. Then, resistance to emamectin benzoate was monitored in field-collected populations of FAW in Brazil from 2003 to 2004 and 2019 to 2021 using different methods: (i) estimating concentration-mortality curves; (ii) determining larval survival at a diagnostic concentration of emamectin benzoate; and (iii) assessing its survivorship on maize leaves sprayed with the field rate of this insecticide. Populations of FAW presented similar susceptibility to emamectin benzoate in 2002 (LC50 from 0.25 to 0.44 μg a.i./mL) and 2003/04 (LC50 from 0.13 to 0.43 μg a.i./mL), not differing from the susceptible reference population (LC50 of 0.22 μg a.i./mL). From 2003 to 2004, larval survival at the diagnostic concentration of emamectin benzoate of 3.2 μg a.i./mL was <1.79%. From 2019 to 2021, the susceptibility to emamectin benzoate in field populations of FAW decreased, with LC50 values ranging from 0.78 to 158.0 μg a.i./mL, indicating resistance ratios up to 632-fold. Larval survival at a diagnostic concentration of emamectin benzoate also increased, reaching up to 81.4%. Larval survival on maize leaves sprayed with the field rate of emamectin benzoate ranged from 16.6 to 88.5% in populations of FAW collected in 2021. Overall, our findings revealed significant shifts towards decrease in the susceptibility to emamectin benzoate in Brazilian populations of FAW, providing robust evidence of field-evolved resistance.

Influence of Temperature Variation on Emamectin Benzoate Toxicity in Different Leucinodes orbonalis Guenee Populations of Punjab

In present study, larval populations of , collected from different regions of Punjab i.e. Amritsar, Kapurthala, Malerkotla, L. orbonalis Ludhiana were exposed to different concentrations of emamectin benzoate at 15, 20, 25 and 30°C for evaluation of LC values. The LC50 50 decreased from lower (15°C) to higher (30°C) temperature for all populations of The positive correlation was observed between L. orbonalis. the temperature coefficient and emamectin benzoate toxicity towards population of which increased with increase in temperature. L. orbonalis, The LC values varied among different populations of i.e. Amritsar populations with higher LC followed by Kapurthala, Malerkotla 50 50 L. orbonalis and Ludhiana populations. The temperature and insecticide exposure history affected the toxicity of emamectin benzoate toxicity for L. orbonalis. L. orbonalis The information would be helpful in developing management strategies for according to prevailing environment conditions.

Biological pesticides and solvents with low toxicity reduce motility and activity of Bursaphelenchus xylophilus

Summary Pine wilt disease (PWD), caused by the pine wood nematode, Bursaphelenchus xylophilus, is an international quarantine forest disease that damages pine forests over extensive areas and causes massive economic losses. To provide valuable guidelines on screening pesticides against B. xylophilus and the selection of common solvents, we investigated the effects of different concentrations of emamectin benzoate, matrine and four solvents (methanol, ethanol, acetone and dimethyl sulfoxide) on the mortality and locomotor behaviour of B. xylophilus. Emamectin abamectin has nematicidal activity and mitigates locomotor activity of B. xylophilus at a low concentration. The LC50 of emamectin benzoate was 0.0354 mg l−1 at 72 h. Bursaphelenchus xylophilus mortality following exposure to matrine was low; however, nematode locomotor activity decreased by 62.5% following exposure to 500 mg l−1 matrine for 8 h. Additionally, B. xylophilus locomotor activity decreased significantly following exposure to 5 and 10% methanol, ethanol, acetone and dimethyl sulfoxide (DMSO) when compared with that of the water control. Emamectin benzoate and matrine, and high concentrations of four solvents (methanol, ethanol, acetone, and DMSO) inhibit B. xylophilus movement, which, in turn, could affect nematode infectivity. Moreover, low concentrations of non-lethal doses of emamectin benzoate should be considered for application in the control of nematodes, with matrine being an environmentally friendly and potentially nematicidal agent.

Lethal and sublethal effects of emamectin benzoate on life-table and physiological parameters of citrus red mite, Panonychus citri.

The citrus red mite (Panonychus citri) is a challenge to manage in citrus orchards due to resistance against several pesticides. There is a necessity therefore to find new pesticides for effective control of P. citri. This study was designed to evaluate the lethal and sublethal effects of emamectin benzoate against P. citri. The results showed that the LC50 of emamectin benzoate to adults of P. citri was 0.35 (0.26-0.43) mg a.i. L-1 and the LC90 was 1.44 (1.16-1.96) mg a.i. L-1. The sublethal concentration exposures (LC10 and LC30) had a significant negative impact on the larval, protonymph, and deutonymph developmental periods. Male longevity was much lower in LC30 treatments than in the controls. Although female longevity was unaffected, the fecundity (eggs per female) was decreased in the sublethal concentration treatments. Results revealed that the adult pre-oviposition period (APOP) and total pre-oviposition period (TPOP) were increased. Other growth parameters r, λ, and R0 decreased, whereas mean generation time (T) increased due to pesticide exposure. The survival rate (Sxj), age-specific fecundity and net maternity, life expectancy (Exj), and reproduction (Vxj) was reduced by LC10 and LC30 exposure. An increase in malondialdehyde (MDA) contents with increasing emamectin benzoate concentration demonstrates that emamectin benzoate induces oxidative stress in P. citri. The activity of antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT) was decreased due to LC30 and LC10 treatments compared to the control. Detoxification enzyme activity (cytochrome P450, glutathione-S-transferases, GST and acetylcholinesterase, AChE) was increased in treated mites compared to the control. This study demonstrates that emamectin benzoate has both a lethal effect on citrus red mite and sublethal effects on its biology and physiology. It is, therefore, potentially an effective pesticide for management of P. citri.

Sublethal concentration of emamectin benzoate inhibits the growth of gypsy moth by inducing digestive dysfunction and nutrient metabolism disorder.

Gypsy moth (Lymantria dispar) is one of the most important pests in the world. Emamectin benzoate (EMB) is widely used in the control of agricultural and forestry pests. Here, we explored the sublethal effects of EMB on gypsy moths in order to better understand the toxicological mechanism of EMB. The sublethal concentration of EMB exposure significantly decreased the larvae body weight. To further explore the mechanism, indicators related to digestion and nutrient metabolism were detected. The results showed that EMB exposure caused midgut damage, reduced the activities of digestive enzymes and changed the content of sugar and amino acids. Moreover, the expression of insulin/phosphoinositide-3-kinase (PI3K)/forkhead box protein O (FoxO) pathway and sugar metabolism-related genes was abnormal. The expression of insulin receptor (InR), chico, PI3K, and protein kinase B (Akt) significantly reduced, and that of phosphatase and tensin homologue (PTEN) and FoxO increased. The expression of glycogen phosphorylase (GP) was upregulation and that of glycogen synthase (GS), trehalase (TRE) and trehalose-phosphate synthase (TPS) were downregulation. All results indicated that EMB inhibits the growth of gypsy moth by inducing midgut injury, digestive dysfunction and nutrient metabolism disorder. In addition, EMB caused midgut injury may be related to apoptosis or a collateral effect of the damage in other tissues, and more extensive and deeper research is still needed to investigate the detailed mechanism. Our finding strengthens the understanding of the sublethal effect of EMB, and provides a theoretical basis for the application of EMB in the prevention and control of gypsy moth.

English

Invasions of the red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) has become a well-known problem for several palm species in date palm-growing states, including Saudi Arabia. Although several control measures have been implemented in efforts against RPW, yet, no approach has proven consistently effective against this invasive pest. Therefore, further efforts are still needed to develop an effective and efficient control method for RPW management and mitigation. The objectives of the present study were to determine emamectin benzoate (ARETOR) efficacy against RPW larval stages, in the laboratory using a diet incorporation bioassay, along with field tests of the Syngenta Tree Micro-Injection Technique. Our laboratory bioassay showed that the median lethal concentration of emamectin benzoate (ARETOR) was 0.30 μg/mL−1 against wild populations of RPW larvae. In the field studies, emamectin benzoate (ARETOR) showed promising effects on RPW mortality for all stages. We found 100% mortality for both larval and pupal stages for all exposure times, except after 2 months, where 86% mortality was observed for larvae. Thus, we conclude that emamectin benzoate (ARETOR) is an effective biopesticide against RPW. Our results show that it killed RPW all stages, also prevented further damage to the healthy tissues of date palms, in addition, provided protection against RPW spread to other neighboring healthy date palms. © 2021 Friends Science Publishers

Emamectin Benzoate Treatment of Hybrid Grouper Infected With Sea Lice in Hong Kong.

Sea lice (Copepoda: Caligidae) are ectoparasites which negatively impact marine aquaculture species around the world. There are a limited number of treatments licensed for use against sea lice in tropical and semi-tropical farmed fish species. Emamectin benzoate (EB) was an effective pharmaceutical drug against sea lice infestations in several salmon industries before resistance to the product developed. This drug has not been extensively tested in marine fish within Asia. The objective of this study was to determine whether this drug could be used to treat oral infections with sea lice in hybrid grouper (Mycteroperca tigris × Epinephelus lanceolatus) cultured in saltwater net-pen sites in Hong Kong. We observed an overall reduction in sea lice infections over time, starting on the last day of the treatment up to the end of our study (i.e., 14 days after the last EB treatment). We also observed a large variation in concentrations of EB in fish on the last day of the treatment, which provides an explanation for the variation in response to the treatment. It also suggests that distribution of the medication to fish in saltwater net-pens is difficult, especially when medication is hand-mixed in the feed and possibly unevenly distributed in the daily rations. Overall, this study provides preliminary evidence that EB could be used to treat sea lice found in Hong Kong and potentially in other regions of SE Asia.

Bioinformatics analysis of structure and function in the MRP gene family and its expression in response to various drugs in Bursaphelenchus xylophilus

Genes homologous to members of the MRP gene family in Caenorhabditis elegans are important in drug resistance. To further explore the molecular mechanism of drug resistance in pine wood nematode (Bursaphelenchus xylophilus), we used bioinformatics approaches to analyze genomic data for B. xylophilus and identified Bx-MRP genes. We predicted the structure and function of the genes and encoded proteins. Using bioinformatics programs to predict and analyze various properties of the predicted proteins, including hydrophobicity, transmembrane regions, phosphorylation sites, and topologically isomeric structures, of these Bx-MRP genes, we determined that they function in transmembrane transport. From the results of RT-qPCR, the Bx-MRP family members confer significant differential resistance to different drug treatments. After treatment with different concentrations of emamectin benzoate, avermectin and matrine, the expression of each gene increased with increasing drug concentrations, indicating that the family members play a positive role in the regulation of multidrug resistance.

Negative effects of the sea lice therapeutant emamectin benzoate at low concentrations on benthic communities around Scottish fish farms

Emamectin benzoate is used as an in-feed treatment for the control of sea lice parasites in all of the main farmed Atlantic salmon (Salmo salar) facilities worldwide (Norway, Chile, Scotland and Canada). Investigations into its effect on non-target benthic fauna resulting from its excretion from farmed fish and uneaten feed have been limited. This paper presents the findings from a study that intended to assess the impact of emamectin benzoate on benthic fauna using a new low detection method for emamectin benzoate. Eight fish farms in the Shetland Isles, Scotland were surveyed, with sediment sampled along transects radiating from the farms analysed for benthic ecology, sediment chemistry and sediment veterinary medicine residues (analysed for emamectin benzoate and teflubenzuron). Canonical Correspondence Analysis (CCA) and Generalised Linear Mixed Modelling (GLMM) were used to assess which environmental parameters observed during the survey had the biggest effect on benthic community composition and abundance, and more specifically crustacean abundance and richness. Emamectin benzoate was found in 97% of samples, demonstrating widespread dispersion in the sediments sampled. The CCA showed that species composition was predominantly ordinated along a gradient of particle size, with a secondary axis dominated by a change in emamectin benzoate and organic carbon enrichment. Peaks in abundance of crustacean species were predicted to be organised along a gradient of emamectin benzoate concentration. The GLMM corroborated this by showing that emamectin benzoate had the strongest negative effect on total crustacean abundance and species richness, though there was some degree of collinearity with organic carbon, that had a smaller effect. Overall, this study shows that, following its use as an in-feed treatment for sea lice, emamectin benzoate residues are more widely distributed in the benthic environment than previously thought, and have a statistically significant effect on benthic ecology at the concentrations observed in this study.

Emamectin benzoate in tilapia: Alternative method for drug incorporation into feed and associated residual depletion study

Due to the lack of regulated drugs for aquaculture, the present study considered specific issues relating to environmental and food safety aspects concerning the potential use of emamectin benzoate (EMA) in freshwater fishes such as tilapia (Oreochromis niloticus) – an important commercial fish species worldwide. The residual depletion of EMA (EMA-B1a) in fillet (muscle plus skin in natural proportions) of tilapia treated with a daily dose of 50 μg/kg BW during seven consecutive days was evaluated. To facilitate this, analytical methods for quantitation of EMA in fish feed and in fish fillet employing LC-MS/MS were developed and validated. To eliminate the risk of EMA leaching from feed into the aquatic environment during fish medication via oral administration, a promising procedure for drug incorporation into feed involving the coating of feed pellets with ethyl cellulose polymer containing EMA was evaluated. The medicated feed exhibited good homogeneity (CV < 2.1%) with negligible EMA release (< LOQ) when the medicated feed remained in the water for up to 20 min. Depletion study analysis revealed the highest EMA concentration obtained in fish fillet to be 13.3 ng/g. Therefore, under the employed rearing conditions of this study, the obtained results did not evidence requirement for a minimum withdrawal period to be proposed considering the maximum residue limit of 100 μg/g for fish muscle. In response to the well-recognized demands and need for new alternative veterinary drugs for use within aquaculture, this study offers impetus for consideration of EMA use in tilapia taking into account environmental contamination and food safety issues.

Evaluating the concentration of emamectin benzoate in Atlantic salmon tissues after sea lice treatments

Pharmaceutical treatments are an important part of integrated sea lice control strategies in all major salmon producing countries in the world. Ensuring that in-feed medication is delivered appropriately, and that fish achieve an adequate tissue concentration of the medication is critical to a successful treatment. The muscle tissue concentration of emamectin benzoate was assessed post SLICE® treatment in 867 Atlantic salmon from 147 treatments. Approximately 90% of the muscle samples that included skin had emamectin benzoate levels above 60 ng/g (ppb); however, only 63.8% of muscle samples without skin were at or above this threshold. Further, we found a wide range of tissue concentrations across our samples, with some fish as high as 398 ng/g. The variation in the emamectin benzoate concentration in our samples was associated with the following factors: feeding rate, whether or not the muscle sample contained skin, year of the sample, laboratory analyzing the tissue, prescribed dose, and condition factor, after controlling for temperature, day of the sample post-treatment, and pen effect. Interestingly, the positive relationship between condition factor and the concentration of emamectin benzoate in the tissue sample was dependent on the dose of medication in the feed. In other words, increasing the dose of emamectin benzoate had a greater effect on the concentration of drug in tissues for fish with a high condition factor compared to fish with a low condition factor. Our findings suggest that the feeding rate and fish feeding behavior within a pen may be important factors to consider when applying medicated feed to fish populations to ensure a more even distribution of medication between animals.

The effects of emamectin benzoate or ivermectin spiked sediment on juvenile American lobsters (Homarus americanus)

This study examined the effects of a range of ½-log concentrations of emamectin benzoate (commercially applied as SLICE®) and ivermectin (commercially applied as IVOMEC®) on juvenile American lobster, Homarus americanus. Phase I of the research assessed acute (up to 4 days) and chronic (30-day) toxicity of sediment dosed with the active ingredients emamectin benzoate (EMB) formulated as SLICE® or ivermectin (IVM) formulated as IVOMEC® at various nominal concentrations (EMB: 15, 48, 150, 475 and 1500 ng g−1 wet sediment; IVM: 3, 9.5, 30, 95 and 300 ng g−1 wet sediment) on juvenile Atlantic lobster (stages IV). Phase II evaluated sublethal effects (e.g., growth, moulting success) of all lobster surviving past the 30 day exposure period, over an additional 41 days. Chemical analysis of EMB and IVM in sediment samples from the exposure tanks revealed a strong linear association (R2 values 0.99 and 0.98 for EMB and IVM, respectively) between nominal dose and measured concentration of compound. EMB exposure concentrations at very high levels (≥ 343.3 ng g−1) were acutely toxic to juvenile lobster such that 100% of lobsters had died after 13 days of exposure. The maximum cumulative mortality of lobsters exposed to the highest concentrations of EMB and IVM was 100% after 10 days and 25 days, respectively. The 10-day LC50 estimates (± 95% CI) for EMB and IVM were 250.23 ± 90.4 and 212.14 ± 202.64 ng g−1, respectively. Using abnormal behaviour as an indicator, the 15-day EC50 estimates (± 95% CI) for EMB and IVM were 96.19 ± 51.42 and 15.82 ± 6.93 ng g−1, respectively. The NOEC (no observed effect concentration) for abnormal behaviour was 0.0 ng g−1 for each product and the LOEC (lowest observed effect concentration) was 8.8 and > 3.0 ng g−1 for EMB and IVM, respectively. Observations on sublethal effects included delayed moulting to stage VI and reduced growth at higher exposure concentrations for both therapeutants. Using failure to moult to stage V or VI as an indicator, the 15-day EC50 estimates (± 95% CI) for EMB and IVM were 32.72 ± 18.26 and 14.00 ± 12.43 ng g−1, respectively. The NOEC for failure to moult to stage V only was 343.3 and 14.7 ng g−1 for EMB and IVM, respectively. Whereas, the LOEC was 1066.7 and > 61.0 ng g−1 for EMB and IVM, respectively. The concentrations of EMB and IVM tested in the present study were acutely toxic to juvenile lobster exposed to the highest dosages (343.3 and 1066.7 ng EMB g−1 and 61.0 and 300.0 ng IVM g−1). There was significant evidence of chronic toxicity, longer exposure increased mortality with LT50 values decreasing with increasing test material concentration.

Emamectin benzoate: Potential larvicide and antifeedant agent against cotton Boll worm Helicoverpa armigera (Lepidoptera: Noctuidae)

Helicoverpa armigera, a global polyphagous pest, attacks a wide variety of crops causing huge agricultural loss. Overuse of conventional insecticides for Helicoverpa control has made Helicoverpa resistant to insecticides leading to more severe attacks on crops diverting interest of researchers to explore alternate control agents. Present study investigates the cidal and antifeedant potential of Emamectin benzoate; a semi-synthetic avermectin derived from the soil actinomycetes, Streptomyces avermitilis; against early IV instars of H. armigera. Larvae were fed on the castor leaf discs (3.5 cm diameter) dipped in different concentrations of Emamectin benzoate; ranging from 0.05 µg/mL-1.5 µg/mL. The leaf disc areas were measured pre-and post-larval feeding to estimate the antifeedant potential of compound. The effect of feeding was also assessed on the survival of larvae by scoring the larval mortality till 96 h. Our investigations showed significant larvicidal potential of Emamectin benzoate against H. armigera revealing respective LC50 values of 0.26 µg/mL, 0.095 µg/mL, 0.043 µg/mL and 0.027 µg/mL after 24, 48, 72 and 96 h feeding. Furthermore, a remarkable decrease of 93.59% was observed in larval feeding potential indicating significant antifeedant efficacy of Emamectin benzoate. A strong correlation between antifeedant index and the Emamectin benzoate concentration resulted in 1.48-fold index reduction with a decrease in concentration. Our results demonstrated efficacy of Emamectin benzoate as an effectual larvicidal and antifeedant agent against H. armigera. Employing selective insecticide can tackle issues of pest resistance and pest resurgence after ascertaining in the fields as Helicoverpa control agent and negating impact on non-target organisms.