Toxicological and biochemical basis of synergism between the entomopathogenic fungus Lecanicillium muscarium and the insecticide matrine against Bemisia tabaci (Gennadius)

Improved control of Trialeurodes vaporariorum using mixture combinations of entomopathogenic fungi and the chemical insecticide spiromesifen

Greenhouse whitefly (Trialeurodes vaporariorum) is a major global pest, causing direct damage to plants and transmitting viral plant diseases. Management of T. vaporariorum is problematic because of widespread pesticide resistance, and many greenhouse growers rely on biological control agents to regulate T. vaporariorum populations. However, these are often slow and vary in efficacy, leading to subsequent application of chemical insecticides when pest populations exceed threshold levels. Combining chemical and biological pesticides has great potential but can result in different outcomes, from positive to negative interactions. In this study, we evaluated co-applications of the entomopathogenic fungi (EPF) Beauveria bassiana and Cordyceps farinosa and the chemical insecticide spiromesifen in laboratory bioassays. Complex interactions between the EPFs and insecticide were described using an ecotoxicological mixtures model, the MixTox analysis. Depending on the EPF and chemical concentrations applied, mixtures resulted in additivity, synergism, or antagonism in terms of total whitefly mortality. Combinations of B. bassiana and spiromesifen, compared to single treatments, increased the rate of kill by 5 days. Results indicate the potential for combined applications of EPF and spiromesifen as an effective integrated pest management strategy and demonstrate the applicability of the MixTox model to describe complex mixture interactions.

Compatibility of synthetic and biological pesticides with a biocontrol agent Phytoseiulus longipes (Acari: Phytoseiidae)

Phytoseiulus longipes is a predatory mite of Tetranychus evansi, which is an invasive pest in Africa and elsewhere. The introduction of this predator in Africa has considerable potential, but little is known about the compatibility of P. longipes with commonly used pesticides. Here, we examined lethal and sublethal effects of two pyrethroids (cypermethrin and deltamethrin), two organophosphates (dimethoate and chlorpyrifos), one nicotinoid (imidacloprid), two acaricides (propargite and abamectin), two naturally derived pesticides (oxymatrine and azadirachtin), and one entomopathogenic fungal-based formulation (Hirsutella thompsonii) on P. longipes eggs and adults. The pesticides were sprayed at their maximum recommended concentrations. Topical exposures to azadirachtin, imidacloprid, propargite, abamectin, oxymatrine, and H. thompsonii significantly reduced the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ)of P. longipes. Pesticide lethal and sublethal effects on the predator were summarized in a reduction coefficient (Ex) for the classification based on IOBC toxicity categories. Results revealed that Azadirachtin and H. thompsonii were slightly harmful effects to adults. Imidacloprid, propargite, abamectin, and oxymatrine were moderately harmful to both eggs and adults. Residual persistence bioassays revealed that 4-day-old residue of azadirachtin had no harmful effect on the predator. Abamectin, oxymatrine, and H. thompsonii became harmless to it 10 days post-spraying, and propargite and imidacloprid were considered harmless after 20 days. Cypermethrin, deltamethrin, dimethoate, and chlorpyrifos were highly harmful to both eggs and adults, persistence remaining high even after 31 days of application. These findings provide valuable insights into decision-making when considering P. longipes for use in IPM programs.

Metarhabditis amsactae: A potential biopesticide isolated from Punjab (India) with potent insecticidal activity and immunomodulatory effects against Galleria mellonella (Lepidoptera: Pyralidae)

A survey was undertaken to isolate entomopathogenic nematodes from Amritsar district of Punjab, India. Out of 20 soil samples collected, two were found positive for the presence of nematodes. 18S and ITS rDNA gene sequencing revealed their identity as Metarhabditis amsactae. To assess its biocontrol potential, Galleria mellonella larvae were treated with concentrations of 20, 40, 80 and 160 IJs/L (infective juveniles/larva) and mortality was recorded from 24 h up to 96 h of nematode exposure. Distilled water without nematodes was used as an untreated control. M. amsactae showed potent larvicidal activity against G. mellonella that was found to be concentration and time dependent. Nematode infection caused 93.33 % larval mortality at 80 IJs/L after 72 h of treatment. 100 % mortality was observed after 96 h. No mortality was observed in control. To evaluate the immunomodulatory effects of M. amsactae, G. mellonella larvae were infected with 100 IJs/L and activities of antioxidant and detoxifying enzymes viz., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX), phenol oxidase (PO), glutathione-S-transferase (GST) and acetylcholine esterase (AChE) were appraised after 12, 24, 36 and 48 h of nematode exposure. Malondialdehyde content was also determined. The results obtained demonstrated a significant elevation in all the enzyme activities at all time intervals in treated larvae when compared with untreated control. MDA levels were also enhanced in response to nematode infection. Thus, the present study revealed high insecticidal potential and immunomodulatory effects of M. amsactae on G. mellonella that should be further explored on other insect pests as well.

The immune response of Locusta migratoria manilensis at different times of infection with Paranosema locustae

Paranosema locustae is an entomopathogenic microsporidia with promising potential for controlling agricultural pests, including Locusta migratoria manilensis. However, it has the disadvantage of having a slow insecticidal rate, and how P. locustae infection impacts the host immune response is currently unknown. The present study investigated the effect of P. locustae on the natural immune response of L. migratoria and the activities of enzymes that protect against oxidative stress. Infection with P. locustae increased the hemocytes and nodulation number of L. migratoria at the initial stage of infection. The hemocyte-mediated modulation of immune response was also affected by a decrease in the number of hemocytes 12 days postinfection. Superoxide dismutase activity in locusts increased in the early stages of infection but decreased in the later stages, whereas the activities of peroxidase (POD) and catalase (CAT) showed opposite trends may be due to their different mechanisms of action. Furthermore, the transcription levels of mRNA of antimicrobial peptide-related genes and phenoloxidase activity in hemolymph in L. migratoria were suppressed within 15 days of P. locustae infection. Overall, our data suggest that P. locustae create a conducive environment for its own proliferation in the host by disrupting the immune defense against it. These findings provide useful information for the potential application of P. locustae as a biocontrol agent.

Synergistic interactions between three insecticides and Beauveria bassiana (Bals.-Criv.) Vuill. (Ascomycota: Hypocreales) in lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae), larvae

Topical applications of insecticides β-cyfluthrin, imidacloprid, and spinosad in combination with Beauveria bassiana (topical and contact filter paper application) induced synergistic interactions in lesser mealworm larvae, increasing mortality and in some cases numbers of larval cadavers exhibiting conidiogenesis. Reduced concentrations (LC10, LC20, LC30) of the insecticides induced sublethal effects in lesser mealworm larvae, inhibiting development (mass, head-capsule width, moulting) after eight days' exposure and movement behaviour (area explored and distance travelled) after 3 h' exposure. The most potent synergist was ß-cyfluthrin, it strongly inhibited larval development and movement while significantly increasing mortality and conidiogenesis in B. bassiana-infected larvae. Imidacloprid also strongly inhibited larval development and movement, but only produced weak short-lived synergistic increases in mortality, with no increase in conidiogenesis. Spinosad induced no effect on development and limited effect on movement, but still induced moderate short-lived synergistic increases in mortality and conidiogenesis. Intoxicated larvae exposed to B. bassiana on filter paper for 3 h showed no synergistic interactions, except when intoxicated by spinosad.

A review on plant-based remedies for the treatment of multiple sclerosis

Multiple sclerosis (MS) is a complex autoimmune disease of central nervous system, which is degenerative in nature usually appears between 20-40years of age. The exact cause of MS is still not clearly known. Loss of myelin sheath and axonal damage are the main features of MS that causes induction of inflammatory process and blocks free conduction of impulses. Till date FDA has approved 18 drugs to treat or modify MS symptoms. These medicines are disease-modifying in nature directed to prevent relapses or slow down the progression of disease. The use of the synthetic drug over an extended period causes undesirable effects that prompt us to look at Mother Nature. Complementary and alternative medicine involves the use of medicinal plants as an alternative to the existing modern medical treatment. However, modern drugs cannot be replaced completely with medicinal plants, but the two types of drugs can be used harmoniously with later one can be added as an adjuvant to the existing treatment. These medicinal plants have the potential to prevent progression and improve the symptoms of MS. Various plants such like Nigella sativa, ginger, saffron, pomegranate, curcumin, resveratrol, ginsenoside have been tested as therapeutics for many neurodegenerative diseases. The purpose of this write-up is to make information available about medicinal plants in their potential to treat or modify the symptoms of MS. Chronically ill patients tend to seek medicinal plants as they are easily available and there is a general perception about these medicines of having fewer undesirable effects.

Effect of Abiotic Factors on Fumosorinone Production from Cordyceps fumosorosea via Solid-State Fermentation

Cordyceps fumosorosea is an important species in the genus of Cordyceps, containing a variety of bioactive compounds, including fumosorinone (FU). This study was a ground-breaking assessment of FU levels in liquid and solid cultures. The present study focused on the impacts of solid-state fermentation (SSF) using solid substrates (wheat, oat, and rice), as well as the effects of fermentation parameters (pH, temperature, and incubation period), on the generation of FU. All the fermentation parameters had significant effects on the synthesis of FU. In a study of 25 °C, 5.5 pH, and 21 days of incubation period combinations calculated -to give maximal FU production, it was found that the optimal values were 25 °C, 5.5 pH, and 21 days, respectively. In a solid substrate medium culture, FU could be produced from SSF. At 30 days, a medium composed of rice yielded the most FU (798.50 mg/L), followed by a medium composed of wheat and oats (640.50 and 450.50 mg/L), respectively. An efficient method for increasing FU production on a large scale could be found in this approach. The results of this study might have multiple applications in different industrial fermentation processes.

Life-table parameters, functional response, flight ability, and cross-generational effects of matrine demonstrate its safety to Hippodamia variegata (Coleoptera: Coccinellidae)

In Xinjiang's cotton growing area of China, previous studies have shown that matrine is a selective botanical insecticide, with high toxicity to Aphis gossypii Glover (Hemiptera: Aphididae) and low toxicity to its dominant natural enemy, Hippodamia variegata Goeze (Coleoptera: Coccinellidae). However, lethal effects alone are not sufficient evidence to justify introducing matrine into local IPM strategies. In this context, we systematically evaluated the safety of matrine to H. variegata by investigating the effects of contact and stomach toxicity of matrine on the lady beetle's life-table parameters, predatory ability, flight ability of parental adults, and cross-generational effects on life-table parameters of the predator's offspring. We found that matrine at 2,000 mg/l did not have any significant negative effects to adult fecundity, longevity, or the predatory capacity of parental adults of H. variegata. Moreover, it is the same for cross-generational effects of matrine on H. variegate. The contact toxicity of matrine significantly reduced the flight time of H. variegata males, but did not significantly affect flight time and average velocity. Our results support the view that matrine is safe to H. variegata and can be recommended for use in the local IPM strategy for control of A. gossipii.

Effect of matrine in MAC-T cells and their transcriptome analysis: A basic study

Matrine, an alkaloid derived from herbal medicine, has a wide range of biological activities, including antibacterial. Matrine was toxic to multiple cells at high concentrations. Bovine mammary epithelial cells (MAC-T) could be used as model cells for cow breast. Matrine was a feasible option to replace antibiotics in the prevention or treatment of mastitis against the background of prohibiting antibiotics, but the safe concentration of matrine on MAC-T cells and the mechanism of action for matrine at different concentrations were still unclear. In this study, different concentrations of matrine (0.5, 1, 1.5, 2, 2.5 and 3 mg/mL) were used to treat MAC-T cells for various time periods (4, 8, 12, 16 and 24 h) and measure their lactic dehydrogenase (LDH). And then the optimal doses (2 mg/mL) were chosen to detect the apoptosis at various time periods by flow cytometry and transcriptome analysis was performed between the control and 2 mg/mL matrine-treated MAC-T cells for 8 hours. The results showed that matrine was not cytotoxic at 0.5 mg/mL, but it was cytotoxic at 1~3 mg/mL. In addition, matrine induced apoptosis in MAC-T cells at 2 mg/mL and the proportion of apoptosis cells increases with time by flow cytometry. RNA-seq analysis identified 1645 DEGs, 676 of which were expressed up-regulated and 969 were expressed down-regulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated the following pathways were linked to matrine-induced toxicity and apoptosis, including cytokine-cytokine receptor interaction pathway, viral protein interaction with cytokine and cytokine receptor, P53 and PPAR pathway. We found 7 DEGs associated with matrine toxicity and apoptosis. This study would provide a basis for the safety of matrine in the prevention or treatment of mastitis.

Comparative transcriptome analysis reveals differences in gene expression in whitefly following individual or combined applications of Akanthomyces attenuatus (Zare & Gams) and matrine

BACKGROUND

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a serious pest of crops in different regions of the world. Our recent studies on the joint application of Akanthomyces attenuatus (a pathogenic insect fungus) and matrine (a botanical insecticide) against B. tabaci have shown promising results. Using RNA sequencing (RNA-Seq), we identified differentially expressed genes involved in whitefly responses to single or mixed applications of A. attenuatus and matrine.

METHODS

In this study, we compared the transcriptome profiles of B. tabaci treated with individual and combined treatments of A. attenuatus and matrine to determine variations in gene expression among whiteflies in response to different treatments.

RESULTS

Transcriptomic data analysis showed differential expression of 71, 1194, and 51 genes in response to A. attenuatus (BtA), matrine (BtM), and A. attenuatus + matrine (BtAM) treatment, respectively. A total of 65 common differentially expressed genes (DEGs) were identified between whiteflies treated with A. attenuatus (BtA) and matrine (BtM). A comparison of DEGs across the three treatments (BtA, BtM, and BtAM) revealed two common DEGs. The results also revealed that AMPK signaling, apoptosis, and drug metabolism pathways are likely involved in whitefly defense responses against A. attenuatus and matrine infection. Furthermore, a notable suppression of general metabolism and immune response genes was observed in whiteflies treated with A. attenuatus + matrine (BtAM) compared to whiteflies treated with individual A. attenuatus (BtA) or matrine (BtM) treatments.

CONCLUSION

Dynamic changes in the number of differentially expressed genes were observed in B. tabaci subjected to different treatments (BtA, BtM, and BtAM). To the best of our knowledge, this is the first report on the molecular interactions between whitefly and individual or combined treatments of A. attenuatus and matrine. These results will further improve our knowledge of the infection mechanism and complex biochemical processes involved in the synergistic action of A. attenuatus and matrine against B. tabaci.

The immunotoxicity of ten insecticides against insect hemocyte cells in vitro

Hemocytes in the hemolymph of insects perform innate immunity, but systematic studies to compare immunotoxicity of pesticides on hemocytes are still few. In this study, an insect hemocyte system was used to assess the impact of pesticides with different modes of action, which included loss of cell viability, inhibition of hemophagocytosis, and reduction of nitric oxide synthase (NOS) activity. Results showed that piericidin A was the most cytotoxic to hemocytes, chlorfluazuron and hexaflumuron were the next. Also, piericidin A, chlorfenapyr, and fipronil had strong inhibitory effects on hemophagocytosis, and the effects of piericidin A and chlorfenapyr were persistent, while that of fipronil was short-lived. Moreover, fenoxycarb and hexaflumuron selectively inhibited granulocyte phagocytosis, tebufenozide only showed inhibition on plasmatocyte phagocytosis, but both inhibitory effects were transient. Furthermore, fenoxycarb and hexaflumuron showed a short-term strong inhibitory effect on the activity of NOS, chlorfenapyr and piericidin A showed a weak induction of NOS activity, while other pesticides exhibited a strong induction. Taken together, piericidin A was the most toxic and imidacloprid was the least toxic to hemocytes, and the alterations in hemocyte functions compromised immunity.

First Record of Aspergillus fijiensis as an Entomopathogenic Fungus against Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae)

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the most widespread and devastating pest species in citrus orchards and is the natural vector of the phloem-limited bacterium that causes Huanglongbing (HLB) disease. Thus, reducing the population of D. citri is an important means to prevent the spread of HLB disease. Due to the long-term use of chemical control, biological control has become the most promising strategy. In this study, a novel highly pathogenic fungal strain was isolated from naturally infected cadavers of adult D. citri. The species was identified as Aspergillus fijiensis using morphological identification and phylogenetic analysis and assigned the strain name GDIZM-1. Tests to detect aflatoxin B1 demonstrated that A. fijiensis GDIZM-1 is a non-aflatoxin B1 producer. The pathogenicity of the strain against D. citri was determined under laboratory and greenhouse conditions. The results of the laboratory study indicated that nymphs from the 1st to 5th instar and adults of D. citri were infected by A. fijiensis GDIZM-1. The mortality of nymphs and adults of D. citri caused by infection with A. fijiensis increased with the concentration of the conidial suspension and exposure time, and the median lethal concentration (LC50) and median lethal time (LT50) values gradually decreased. The mortality of D. citri for all instars was higher than 70%, with high pathogenicity at the 7th day post treatment with 1 × 108 conidia/mL. The results of the greenhouse pathogenicity tests showed that the survival of D. citri adults was 3.33% on the 14th day post-treatment with 1 × 108 conidia/mL, which was significantly lower than that after treatment with the Metarhizium anisopliae GDIZMMa-3 strain and sterile water. The results of the present study revealed that the isolate of A. fijiensis GDIZM-1 was effective against D. citri and it provides a basis for the development of a new microbial pesticide against D. citri after validation of these results in the field.

Larvicidal, antioxidant and biotoxicity assessment of (2-(((2-ethyl-2 methylhexyl)oxy)carbonyl)benzoic acid isolated from Bacillus pumilus against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus

Mosquitoes are a vector for many dreadful diseases known for their public health concern. The continued use of synthetic insecticides against vector control has led to serious environmental impacts, human health problems, and the development of insect resistance. Hence, alternative mosquito control methods are needed to protect the environment and human health. In the present study, the bioefficacy of (2-(((2-ethyl-2 methylhexyl)oxy)carbonyl) benzoic acid isolated from Bacillus pumilus were tested against Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi. The isolated bioactive compound was characterized through thin layer chromatography (TLC), UV-visible spectroscopy (UV), Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gas chromatography-mass spectrometry analysis. The pure compound caused a high percent mortality rate in a dose-dependent manner, the obtained values were 96, 82, 69, 50 and 34%; 86, 72, 56, 43, and 44%; 100, 90, 83, 70 and 56% against Ae. aegypti, Cx. quinquefasciatus, and An. stephensi respectively. The effective lethal concentration values (LC₅₀) were 13.65, 14.90 and 9.64 ppm against Ae. aegypti, Cx. quinquefasciatus, An. Stephensi, respectively. The effect of (2-(((2-ethyl-2 methylhexyl)oxy)carbonyl) benzoic acid significantly increased the superoxide dismutase, catalase, α, β esterase and Glutathione-S-transferase level after 24 h of the treatment period. The comet assay confirmed that isolated compound causes DNA damage in all tested insects. Histopathological examinations of treated larvae showed shrunken body posture, damaged epithelial cells and microvillus as compared to control organisms. The biosafety of the isolated compound was assessed against G. affinis and did not produce mortality which confirmed that the activity of the isolated compound is species specific. The current study concludes that the critical success factors of new insecticidal agent development are based on the eco-compatibility and alternative tools for the pesticide producing industry.

Physiological and Molecular Response Modifications by Ultraviolet-C Radiation in Plutella xylostella and Its Compatibility with Cordyceps fumosorosea

Ultraviolet-C (UV-C) radiation significantly impacts living organisms. UV-C radiation can also be used as a pest management tool. Therefore, this study was designed to investigate the effect of UV-C radiation on the physiology and gene expression level of Plutella xylostella, a destructive vegetable pest. Results showed that, after exposure to UV-C radiation for 3, 6, 12, and 24 h, the activity of SOD (superoxide dismutase) and CAT (catalase) of P. xylostella increased, while the activity of PPO (polyphenol oxidase), POD (peroxidase), AChE (acetylcholinesterase), CarE (carboxylesterase), and ACP (acid phosphatase) decreased with increased exposure time. Correlation coefficient analyses indicated that the activity of CAT correlated positively, while PPO and CarE correlated negatively, with exposure time. Gene regulation analysis via qRT-PCR confirmed a significant increase in regulation in CAT, CarE, and PPO-related genes. We also investigated the effect of UV-C exposure on the virulence of Cordyceps fumosorosea against P. xylostella. Here, results indicated that when the fungal treatment was applied to larvae before UV-C radiation, the virulence of C. fumosorosea was significantly reduced. However, this decline in virulence of C. fumosorosea due to UV-C exposure remained only for one generation, and no effect was observed on secondary infection. On the other hand, when larvae were exposed to UV-C radiation before fungal application, the mortality rate significantly increased as the exposure time to UV-C radiation increased. From the current study, it could be concluded that UV-C exposure suppressed the immunity to P. xylostella, which later enhanced the virulence of entomopathogenic fungi. Moreover, the study also suggested that UV irradiation is an effective pest management tool that could be incorporated into pest management strategies, which could help reduce pesticide application, be economically beneficial for the farmer, and be environmentally safe.

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.

Effect of entomopathogenic fungi of the genus Lecanicillium on behavioral reactions and average per-day fecundity of the predatory bug Orius laevigatus Fieber (Heteroptera, Anthocoridae)

The results of studying the effect of spores and mycelium of entomopathogenic fungi of the genus Lecanicillium on the behavioral responses of predatory bugs Orius laevigatus and their fecundity are provided. In a laboratory experiment, the location of the bug adults was assessed after 24 hours, as well as the average daily fecundity of females with a free choice between a bean leaf with agar (control) and a bean leaf with sporulating fungal mycelium (experiment). It was found that the neutral reaction prevailed in the behavior of the bugs. The repellent reaction of predators was caused by the mycelium of three strains: Vl 29 (L. lecanii), ARSEF 2332 (L. dimorphum), Vit 71 (L. attenuatum); the index of aggregation ranged from -40.7 to -50 (P<0.05). Strain Vl 5 (L. lecanii), index of aggregation+43.3, caused a significant attractive reaction. The strains causing a repellant reaction of bugs did not affect the average per-day fecundity of females. Only two strains Vl 72 of L. muscarium and Vl 79 of L. dimorphum caused a significant decrease in the fecundity of O. laevigatus, while the reaction of bugs to the mycelium of these strains was neutral. In the absence of a negative effect of fungi on the fecundity of bugs, the combined use of these biological agents may be promising.

Testing new compounds for efficacy against Varroa destructor and safety to honey bees (Apis mellifera)

BACKGROUND

Varroa destructor is among the greatest threats to honey bee health worldwide. Acaricides used to control Varroa are becoming increasingly ineffective due to resistance issues, prompting the need for new compounds that can be used for control purposes. Ideally, such compounds would exhibit high toxicity to Varroa while maintaining relatively low toxicity to bees and beekeepers. We characterized the lethal concentrations (LC₅₀ ) of amitraz, matrine, FlyNap®, the experimental carbamates 2-((2-ethylbutyl)thio)phenyl methylcarbamate (1) and 2-(2-ethylbutoxy)phenyl methylcarbamate (2), and dimethoate (positive control) for Varroa using a glass vial assay. The test compounds also were applied to honey bees using an acute contact toxicity assay to determine the adult bee LD₅₀ for each compound.

RESULTS

Amitraz was the most toxic compound to Varroa, but carbamate 2 was nearly as active (within 2-fold) and the most selective due to its lower bee toxicity, demonstrating its promise as a Varroa control. While carbamate 1 was less toxic to honey bees than was amitraz, it was also 4.7-fold less toxic to the mites. Both matrine and FlyNap® were relatively ineffective at killing Varroa and were moderately toxic to honey bees.

CONCLUSION

Additional testing is required to determine if carbamate 2 can be used as an effective Varroa control. As new chemical treatments are identified, it will be necessary to determine how they can be utilized best alongside other control techniques as part of an integrated pest management program. © 2021 Society of Chemical Industry.

Synthesis of Metarhizium anisopliae–Chitosan Nanoparticles and Their Pathogenicity against Plutella xylostella (Linnaeus)

Nanotechnology is increasingly being used in areas of pesticide production and pest management. This study reports the isolation and virulence of a new Metarhizium anisopliae isolate SM036, along with the synthesis and characterization of M. anisopliae–chitosan nanoparticles followed by studies on the efficacy of nanoparticles against Plutella xylostella. The newly identified strain proved pathogenic to P. xylostella under laboratory conditions. The characterization of M. anisopliae–chitosan nanoparticles through different analytical techniques showed the successful synthesis of nanoparticles. SEM and HRTEM images confirmed the synthesis of spherical-shaped nanoparticles; X-ray diffractogram showed strong peaks between 2θ values of 16–30°; and atomic force microscopy (AFM) analysis revealed a particle size of 75.83 nm for M. anisopliae–chitosan nanoparticles, respectively. The bioassay studies demonstrated that different concentrations of M. anisopliae–chitosan nanoparticles were highly effective against second instar P. xylostella under laboratory and semi-field conditions. These findings suggest that M. anisopliae–chitosan nanoparticles can potentially be used in biorational P. xylostella management programs.

Integrated Pest Management Control of Varroa destructor (Acari: Varroidae), the Most Damaging Pest of (Apis mellifera L. (Hymenoptera: Apidae)) Colonies

Varroa destructor is among the greatest biological threats to western honey bee (Apis mellifera L.) health worldwide. Beekeepers routinely use chemical treatments to control this parasite, though overuse and mismanagement of these treatments have led to widespread resistance in Varroa populations. Integrated Pest Management (IPM) is an ecologically based, sustainable approach to pest management that relies on a combination of control tactics that minimize environmental impacts. Herein, we provide an in-depth review of the components of IPM in a Varroa control context. These include determining economic thresholds for the mite, identification of and monitoring for Varroa, prevention strategies, and risk conscious treatments. Furthermore, we provide a detailed review of cultural, mechanical, biological, and chemical control strategies, both longstanding and emerging, used against Varroa globally. For each control type, we describe all available treatments, their efficacies against Varroa as described in the primary scientific literature, and the obstacles to their adoption. Unfortunately, reliable IPM protocols do not exist for Varroa due to the complex biology of the mite and strong reliance on chemical control by beekeepers. To encourage beekeeper adoption, a successful IPM approach to Varroa control in managed colonies must be an improvement over conventional control methods and include cost-effective treatments that can be employed readily by beekeepers. It is our intention to provide the most thorough review of Varroa control options available, ultimately framing our discussion within the context of IPM. We hope this article is a call-to-arms against the most damaging pest managed honey bee colonies face worldwide.

Synergistic Interaction between the Entomopathogenic Fungus Akanthomyces attenuatus (Zare & Gams) and the Botanical Insecticide Matrine against Megalurothrips usitatus (Bagrall)

The excessive use of synthetic chemicals for Megalurothrips usitatus (Bagrall) management has resulted in the development of insecticide resistance as well as adverse effects to the natural ecosystem. This has driven the need to develop alternative pest control strategies. This study reports a synergistic interaction between the entomopathogenic fungus Akanthomyces attenuatus (Zare & Gams) and the botanical insecticide matrine against M. usitatus. The results revealed that the germination rate and colony growth of A. attenuatus were inhibited by higher matrine concentrations. Percentage mortalities of M. usitatus following application of A. attenuatus and matrine showed a dose mortality effect. After five days of treatment, all concentrations of matrine combined with different concentrations of A. attenuatus, except one combination (matrine 0.25 mg/mL + 1 × 10⁷ conidia/mL), showed synergistic effect. The activities of acetylcholinesterase and antioxidant enzymes (superoxide dismutase, catalase and peroxidase) in M. usitatus, in response to individual or combined application of A. attenuatus and matrine at the end of the experimental period, were significantly lower than controls. The findings confirm the synergistic action of A. attenuatus and matrine against M. usitatus along with the biochemical phenomenon possibly regulating the synergistic effect.

New quinolizidine alkaloid and insecticidal activity of Sophora secundiflora and Sophora tomentosa against Culex pipiens (Diptera: Culicidae)

Phytochemical investigation of Sophora secundiflora alkaloid fraction led to isolation of one new quinolizidine alkaloid (1) 13-methoxyanagyrine together with six known ones (2-7). The insecticidal activity of 70% methanol extract of leaves of S. secundiflora, S. tomentosa and the isolated alkaloids were assessed against 3^rd instar larvae of Culex pipiens (Diptera: Culicidae) using different concentrations and mortality rate was recorded. Sophora tomentosa extract showed highest mortality rate with median lethal concentration LC₅₀ 3.11 ppm after 24 h and 0.66 ppm after 48 h and anagyrine (6) exhibited remarkably insecticidal activity with LC₅₀ value of 3.42 ppm after 24 h of exposure. Additionally, cytotoxic activity of alkaloid fraction of S. secundiflora, S. tomentosa and isolated alkaloids was also studied using crystal violet assay against MCF-7 and HEPG-2 cell lines. Anagyrine (6) exhibited IC₅₀ values of 27.3 ± 0.7 and 30.2 ± 0.9 µg/mL against MCF-7 and HEPG-2 cancer cells, respectively.

Matrine: A review of its pharmacology, pharmacokinetics, toxicity, clinical application and preparation researches

ETHNOPHARMACOLOGICAL RELEVANCE

"Dogel ebs" was known as Sophora flavescens Ait., which has been widely utilized in the clinical practice of traditional Chinese Mongolian herbal medicine for thousands of years. Shen Nong's Materia Medica (Shen Nong Ben Cao Jing in Chinese pinyin) recorded that it is bitter in taste and cold in nature with the effect of clearing heat and eliminating dampness, insecticide, diuresis. Due to its extensive application in the fields of ethnopharmacological utilization, the pharmaceutical researches of Sophora flavescens Ait.s keeps deepening. Modern pharmacological studies have exhibited that matrine, which is rich in this traditional herbal medicine, mediates its main biological properties.

AIMS OF THE REVIEW

This review aimed at summarizing the latest and comprehensive information of matrine on the pharmacology, pharmacokinetics, toxicity, clinical application and preparation researches to explore the therapeutic potential of this natural ingredient. In addition, outlooks and perspective for possible future researches that related are also discussed.

MATERIALS AND METHODS

Related information concerning matrine was gathered from the internet database of Google scholar, Pubmed, ResearchGate, Web of Science and Wiley Online Library with the keywords including "matrine", "pharmacology", "toxicology" and "pharmacokinetics", "clinical application", etc. RESULTS: Based on literatures, matrine has a variety of pharmacological effects, including anti-cancer, anti-inflammatory, anti-microbial, detoxification and so on. Nevertheless, there are still some doubts about it due to the toxicity and questionable bioavailability that does exist.

CONCLUSIONS

Future researches directions probably include elucidate the mechanism of its toxicity and accurately tracing the in vivo behavior of its drug delivery system. Without doubt, integration of toxicity and efficiency and structure modification based on it are also pivotal methods to enhance pharmacological activity and bioavailability.

Synthesis of Cordyceps fumosorosea-Biochar Nanoparticles and Their Effects on Growth and Survival of Bemisia tabaci (Gennadius)

Nanotechnology can offer an environmentally sustainable alternative to synthetic chemicals for pest management. Nano-formulations of different microbial pest control agents have been effective against several insect pests. Synthesis of Cordyceps fumosorosea-biochar (BC) nanoparticles and their bio-efficacy against Bemisia tabaci was observed during this study. The characterization of C. fumosorosea-BC nanoparticles through different analytical techniques showed successful synthesis of nanoparticles. UV spectroscopy showed a characteristic band of surface plasmon between 350 and 400 nm; SEM images confirmed the synthesis of spherical shaped nanoparticles; X-ray diffractogram showed strong peaks between 2θ values of 20°–25°; and atomic force microscopy (AFM) analysis revealed particle size of 49.151 nm. The bioassay studies demonstrated that different concentrations of C. fumosorosea-BC nanoparticles caused significant reduction in hatchability of B. tabaci eggs as well as survival of immatures emerging from treated eggs when compared with controls. The results also revealed that C. fumosorosea-BC nanoparticles were highly pathogenic against 2nd and 3rd instar nymphs and pupae of B. tabaci having LC₅₀ values of 6.80, 7.45, and 8.64 ppm, respectively. The LT₅₀ values for 20 ppm concentration of C. fumosorosea-BC nanoparticles against 2nd and 3rd instar nymphs, and pupae of B. tabaci were 3.25 ± 0.29, 3.69 ± 0.52, and 4.07 ± 0.51 days, respectively. These findings suggest that C. fumosorosea-BC nanoparticles can potentially be used in biorational B. tabaci management programs.

Bradyrhizobium arachidis mediated enhancement of (oxy)matrine content in the medicinal legume Sophora flavescens

Effect of rhizobial inoculation and nitrate application on the content of bioactive compounds in legume plants is an interesting aspect for interactions among microbes, plants and chemical fertilizers, as well as for cultivated practice of legumes. In this study, nitrate (0, 5 and 20 mmol l^-1 ) and Bradyrhizobium arachidis strain CCBAU 051107^T were applied, individually or in combination, to the root rhizosphere of the medicinal legume Sophora flavescens Aiton (SFA). Then the plant growth, nodulation and active ingredients including (oxy)matrine of SFA were determined and compared. Rhizobial inoculation alone significantly increased the numbers and fresh weight of root nodules. Nodulation was significantly inhibited due to nitrate (5 and 20 mmol l^-1 ). Only oxymatrine was detected in the control plants without rhizobial inoculation and nitrate supplement, while both oxymatrine and matrine were synthesized in plants treated with inoculation of B. arachidis or supplied with nitrate. The content of oxymatrine was the highest in plants inoculated solely with rhizobia and was not significantly altered by additional application of nitrate. Combinations of B. arachidis inoculation and different concentrations of nitrate did not significantly change the concentrations of (oxy)matrine in the plant. In conclusion, sole rhizobial inoculation was the best approach to increase the contents of key active ingredients oxymatrine and matrine in the medicinal legume SFA.

Efficacy of biorational insecticides against Bemisia tabaci (Genn.) and their selectivity for its parasitoid Encarsia formosa Gahan on Bt cotton

The toxicity of seven biorational insecticides [five insect growth regulators (Buprofezin, Fenoxycarb, Pyriproxyfen, Methoxyfenozide, and Tebufenozide) and two oil-extracts of neem and bitter gourd seeds] against Bemisia tabaci and their selectivity for its parasitoid, Encarsia formosa were evaluated in laboratory and field conditions for 2 years (2018-2019) in Pakistan. Toxicity results demonstrate that Pyriproxyfen, Buprofezin, and Fenoxycarb proved to be effective (80-91% mortality and 66.3-84.2% population-reduction) against B. tabaci followed by Methoxyfenozide, Tebufenozide (50-75% mortality and 47.8-52.4% population-reduction), and then oil-extracts of neem and bitter gourd (25-50% mortality and 36.5-39.8% population-reduction) in the laboratory [72 h post-application exposure interval (PAEI)] and field trails (168 h PAEI), respectively. All tested biorationals, except Methoxyfenozide [(slightly-harmful/Class-II), i.e., causing mortality of parasitoids between a range of 25-50%] and Tebufenozide [(moderately-harmful/Class-III), i.e., causing mortality of parasitoids between the ranges of 51-75%], proved harmless/Class-I biorationals at PAEI of 7-days in the field (parasitism-reduction < 25%) and 3-days in the lab (effect < 30%). In laboratory bioassays, exposure of parasitized-pseudopupae and adult-parasitoids to neem and bitter gourd oils demonstrated that these compounds proved harmless/Class-I biorationals (< 30% mortality). Alternatively, Pyriproxyfen, Buprofezin, Fenoxycarb, Methoxyfenozide, and Tebufenozide were slightly-harmful biorationals (30-79% mortality) against the respective stages of E. formosa. We conclude that most of the tested biorationals proved harmless or slightly harmful to E. formosa, except tebufenozide after PAEI of 7-days (168 h) in the field and, therefore, may be used strategically in Integrated Pest Management (IPM) of B. tabaci.

Fungus Metarhizium robertsii and neurotoxic insecticide affect gut immunity and microbiota in Colorado potato beetles

Fungal infections and toxicoses caused by insecticides may alter microbial communities and immune responses in the insect gut. We investigated the effects of Metarhizium robertsii fungus and avermectins on the midgut physiology of Colorado potato beetle larvae. We analyzed changes in the bacterial community, immunity- and stress-related gene expression, reactive oxygen species (ROS) production, and detoxification enzyme activity in response to topical infection with the M. robertsii fungus, oral administration of avermectins, and a combination of the two treatments. Avermectin treatment led to a reduction in microbiota diversity and an enhancement in the abundance of enterobacteria, and these changes were followed by the downregulation of Stat and Hsp90, upregulation of transcription factors for the Toll and IMD pathways and activation of detoxification enzymes. Fungal infection also led to a decrease in microbiota diversity, although the changes in community structure were not significant, except for the enhancement of Serratia. Fungal infection decreased the production of ROS but did not affect the gene expression of the immune pathways. In the combined treatment, fungal infection inhibited the activation of detoxification enzymes and prevented the downregulation of the JAK-STAT pathway caused by avermectins. The results of this study suggest that fungal infection modulates physiological responses to avermectins and that fungal infection may increase avermectin toxicosis by blocking detoxification enzymes in the gut.

1 H NMR-based metabonomic evaluation of the pesticides camptothecin and matrine against larvae of Spodoptera litura

BACKGROUND

Camptothecin (CPT) and matrine (MAT) have potential as botanical pesticides against several pest species. However, the mechanisms of metabolic and physiological changes in pests induced by CPT and MAT are unknown. In this study, a toxicological test, an NMR-based metabolomic study, an enzymatic test, and an RT quantitative PCR (RT-qPCR) experiment were all conducted to examine the effect of CPT and MAT on Spodoptera litura.

RESULTS

CPT (0.5-1%) exerted high toxicity against larvae of S. litura and caused growth stagnation and high mortality of larvae. A variety of metabolites were significantly influenced by 0.5% CPT, including several energy-related metabolites such as trehalose, lactate, succinate, citrate, malate, and fumarate. In contrast, MAT showed low toxicity against larvae and induced almost no changes in hemolymph metabolites of S. litura. Enzymatic tests showed that trehalase activity was significantly decreased in larvae after feeding with 0.5% CPT. RT-qPCR showed that the transcription levels of alanine aminotransferase, malate dehydrogenase, and isocitrate dehydrogenase were decreased while lactate dehydrogenase was increased in the 0.5% CPT-treated group.

CONCLUSIONS

These data indicate that one of the important mechanisms of CPT against S. litura larvae is via the inhibition of trehalose hydrolysis and glycolysis. Our findings also suggest that CPT exhibits a stronger toxicological effect than MAT against S. litura, which provides basic information for the application of CPT in the control of S. litura or other lepidoptera pests.

Toxicity and Biological Effects of Beauveria brongniartii Fe0 Nanoparticles against Spodoptera litura (Fabricius)

Simple Summary

Metal-based nanoparticles of different microbial pest control agents have been effective against several pests. This study reports the synthesis of Beauveria brongniartii based Fe⁰ nanoparticles (Fe⁰NPs) and their bio-efficacy against Spodoptera litura that was observed during this study. The median lethal concentration (LC₅₀) of Fe⁰NPs against S. litura after 7 days was 59 ppm, whereas the median survival time (LT₅₀) for 500 ppm concentrations of Fe⁰NPs was 2.93 days. B. brongniartii Fe⁰NPs caused a significant reduction in feeding and growth parameters as well as detoxifying enzyme production by S. litura at the end of the experimental period. These findings suggest that B. brongniartii Fe⁰NPs can potentially be used in environmentally friendly S. litura management programs.

Abstract

Nanotechnology has clear potential in the development of innovative insecticidal products for the biorational management of major insect pests. Metal-based nanoparticles of different microbial pest control agents have been effective against several pests. Synthesis of Beauveria brongniartii based Fe⁰ nanoparticles (Fe⁰NPs) and their bio-efficacy against Spodoptera litura was observed during this study. Beauveria brongniartii conidia were coated with Fe⁰NPs and characterized by applying a selection of different analytical techniques. Ultraviolet (UV) spectroscopy showed the characteristic band of surface plasmon at 430 nm; Scanning electron microscopy (SEM) images showed spherical shaped nanoparticles with a size ranging between 0.41 to 0.80 µm; Energy-dispersive X-ray (EDX) spectral analysis revealed characteristic Fe peaks at 6.5 and 7.1 Kev; the X-ray diffractogram showed three strong peaks at 2θ values of 45.72°, 64.47°, and 84.05°. The bioassay studies demonstrated that mortality of 2nd instar S. litura larvae following Fe⁰NPs treatment increased with increasing concentrations of Fe⁰NPs at different time intervals. The median lethal concentration (LC₅₀) values of Fe⁰NPs against S. litura after seven days of fungal treatment was 59 ppm, whereas median survival time (LT₅₀) values for 200 and 500 ppm concentrations of Fe⁰NPs against S. litura seven days post-treatment were 5.1 and 2.29 days, respectively. Beauveria brongniartii-Fe⁰NPs caused significant reductions in feeding and growth parameters (relative growth rate, relative consumption rate, and efficiency of conversion of ingested food) of S. litura. Beauveria brongniartii Fe⁰NPs induced reduction in glutathione-S-transferase activities throughout the infection period whereas activities of antioxidant enzymes decreased during later periods of infection. These findings suggest that B. brongniartii Fe⁰NPs can potentially be used in biorational S. litura management programs.

Biological Impact and Enzyme Activities of Spodoptera litura (Lepidoptera: Noctuidae) in Response to Synergistic Action of Matrine and Beauveria brongniartii

Matrine, a naturally occurring heterocyclic compound, has been shown to enhance the pathogenicity of the entomopathogenic fungus Beauveria brongniartii against Spodoptera litura. In the current study, the biological impacts and synergism activities of these two agents on nutritional efficiency and antioxidant enzymes in S. litura were explored. Our results showed a high antifeedant activity of B. brongniartii and matrine on S. litura. The S. litura larvae were unable to pupate and emerge when treated with combinations of matrine and B. brongniartii. Following on, we measured the activities of five important antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), acetylcholinesterase (AChE), and glutathione-S-transferase (GST)] when treated with B. brongniartii SB010 (1 × 109 spores/ml), matrine (0.5 mg/ml), and B. brongniartii SB010 (1 × 109 spores/ml) + matrine (0.5 mg/ml). The results indicated the detoxification activity of the five enzymes in the fat body and hemolymph of S. litura when facing a combined B. brongniartii and matrine challenge. The activities of the enzymes were significantly lower than that of the control group 7 days post-treatment, indicating the inhibitory effect of the two xenobiotics. Matrine had better inhibition effects than B. brongniartii in a majority of the trials. The improved detoxification activity of the five enzymes may be the internal mechanism of synergism of matrine on B. brongniartii.

Evaluation of Botanicals for Management of Piercing-Sucking Pests and the Effect on Beneficial Arthropod Populations in Tea Trees Camellia sinensis (L.) O. Kuntze (Theaceae)

The tea green leafhopper Empoasca onukii Matsuda (Hemiptera: Cicadellidae), the orange spiny whitefly, Aleurocanthus spiniferus (Quaintanca) (Hemiptera: Aleyrodidae), and the green plant bugs Apolygus lucorum Meyer-Dür (Hemiptera: Miridae) are the important piercing-sucking herbivores in tea trees Camellia sinensis (L.) O. Kuntze (Theaceae). The goal of this study was to evaluate the laboratory toxicities and field control efficacies of botanical insecticides including matrine, azadirachtin, veratrine, and pyrethrin to three tea pests. Via leaf-dip bioassay, toxicity tests with botanical insecticides indicated that there were significant differences between the LC50 values for botanical insecticides within the same insect species. Matrine had the highest toxicity to E. onukii, A. spiniferus, and A. lucorum with the LC50 values of 2.35, 13.10, and 44.88 mg/liter, respectively. Field tests showed that, among four botanical insecticides, matrine at dose of 9 g a.i. ha-1 can significantly reduce the numbers of E. onukii and A. spiniferus and the infestation of A. lucorum on the tea plants. Furthermore, botanical insecticides matrine and azadirachtin had no obvious influence on the coccinellids, spiders, and parasitoids densities in tea plantations. The results of this study indicated that use of botanical insecticides, such as matrine, has the potential to manipulate the population of E. onukii, A. spiniferus, and A. lucorum and will be an effective and environmentally compatible strategy for the control of tea pests.

Semi-synthesis and characterization of some new matrine derivatives as insecticidal agents

BACKGROUND

Matrine is an important traditional plant-derived insecticide with broad-spectrum activity. However, due to its moderate activity, matrine is mainly applied in combination with other pesticides. In order to discover new potential natural-product-based crop protection agents, a series of matrine derivatives characterized by cyclohexylamine group were synthesized to screen their insecticidal activity against seven typically agricultural pests.

RESULTS

The structural configurations of compounds were characterized by IR, ¹ H NMR, ¹³ C NMR, MS and XRD, with the pure yields of 42%, 65% and 71%, respectively. Although all compounds showed poor insecticidal activity against five lepidoptera pests, the compounds 2 and 4 displayed remarkable insecticidal activities against Lipaphis erysimi and Mulberry Root-Knot Nematode with a concentration-dependent manner within 0.5~1.5 mg/ mL. Compared with matrine (60%), compounds 2 and 4 exhibited potent insecticidal activities against L. erysimi, with a corrected mortality of 83.3% and 89.7%, respectively. They also showed excellent control effects on Mulberry Root-Knot Nematode, with corrected mortality as high as 88% and 80%, respectively.

CONCLUSION

All four synthesized matrine derivatives showed poor insecticidal activity against five lepidoptera pests, but the compounds 2 and 4 exhibited much stronger insecticidal activities against L. erysimi and Mulberry Root-Knot Nematode than matrine. Combined with the structural characteristics of compounds 1~4, we conclude that 4-methylcyclohexylamine, not the carbon disulfide group or cyclohexylamine group alone, mainly contributed to the improvement of insecticidal activities of matrine derivatives against these two agricultural pests. This work provides a direction and foundation for structural optimization of the matrine pesticides in the future. © 2020 Society of Chemical Industry.

Endophytic Isolates of Cordyceps fumosorosea to Enhance the Growth of Solanum melongena and Reduce the Survival of Whitefly (Bemisia tabaci)

This study reports the effects of seed treatment with Cordyceps fumosorosea on seed germination, growth, colonization of eggplant (Solanum melongena), and growth of Bemisia tabaci (feeding on fungal colonized eggplant leaves). Germination rates of eggplant seeds were similar among different treatments. The growth parameters such as root length, shoot length, and number of leaves) differed significantly after 15, 30, and 60 days of seed treatment. The total dry weight of eggplant in response to treatment with C. fumosorosea isolates increased significantly when compared with the control. Both isolates of C. fumosorosea colonized different plant tissues, although the extent of colonization decreased during the experimental period. The colonization of eggplants by both C. fumosorosea isolates resulted in a significant reduction of B. tabaci incidence. This study possibly provides the first report of increased plant growth and increased insect mortality in eggplants inoculated with C. fumosorosea isolates.

Preparation of Matrinic/Oxymatrinic Amide Derivatives as Insecticidal/Acaricidal Agents and Study on the Mechanisms of Action against Tetranychus cinnabarinus

In continuation of our program to develop natural-product-based pesticidal candidates, matrinic/oxymatrinic amides were obtained through structural optimization of matrine. N'-(4-Fluoro)phenyl-N-(4-bromo)phenylsulfonyloxymatrinic amide (IIm) showed potent insecticidal activity against Mythimna separata. N-(Un)substituted phenylsulfonylmatrinic acids (3a-c) exhibited promising acaricidal activity against Tetranychus cinnabarinus. By qRT-PCR analysis of nAChR subunits and AChE genes and determination of AChE activity of (un)treated T. cinnabarinus, it suggested that the open lactam ring of matrine and carboxyl group and (4-methyl)phenylsulfonyl of N-(4-methyl)phenylsulfonylmatrinic acid (3b) were necessary for action with α2, α4, α5, and β3 nAChR subunits; compound 3b was an inhibitor of AChE in T. cinnabarinus, and AChE was one possible target of action in T. cinnabarinus against 3b; and compound 3b may be an antagonist of nAChR and AChE in T. cinnabarinus.

Matrine Enhances the Pathogenicity of Beauveria brongniartii Against Spodoptera litura (Lepidoptera: Noctuidae)

The repetitive application of pesticides at high doses against Spodoptera litura Fabricius has resulted in development of pesticide resistance and harmful effects to the natural environmental. Hence, finding alternate pest control strategies, such as entomopathogenic fungi or their application in combination with other natural chemicals, is of great importance to solve the abovementioned problems. This study presents the toxic effects of Beauveria brongniartii and matrine (individual or in combination with each other) against tobacco cutworm (S. litura). Different matrine treatments caused a dose dependent increase in S. litura mortality at different time intervals. The biological parameters of B. brongniartii (germination rate and average daily mycelia growth) were not inhibited by different matrine treatments. Different conidial concentrations of B. brongniartii caused significantly different mortalities of 2nd instar S. litura larvae at different time intervals. Different combined treatments of B. brongniartii and matrine showed a significant synergistic effect against S. litura under laboratory and semi-field conditions. The current findings showed a strong synergistic action for combined application of B. brongniartii and matrine against S. litura. Our results will provide baseline information on combined application of entomopathogenic fungi and natural chemicals in integrated pest management programs against S. litura.

Isaria fumosorosea-based zero-valent iron nanoparticles affect the growth and survival of sweet potato whitefly, Bemisia tabaci (Gennadius)

BACKGROUND

Nanoparticles can be used for effective pest management as a combined formulation of metal and some other material that has proven efficacy against a given pest. This study reports the synthesis, characterization and efficacy of Isaria fumosorosea-based zero-valent iron (ZVI) nanoparticles against sweet potato whitefly Bemisia tabaci (Gennadius).

RESULTS

The I. fumosorosea-ZVI nanoparticles showed a characteristic surface plasmon absorption band at 470 nm during UV-visible spectroscopy. The scanning electron micrographs of nanoparticles showed spherical shaped nanoparticles with sizes ranging between 1.71 and 3.0 µm. The EDX analysis showed the characteristic peak of iron at 0.6 and 6.8 KeV. The XRD analysis showed characteristic peaks at 44.72°, 65.070°, 82.339° and 82.65°. The bioassay results indicated that the percentage of larval mortality of B. tabaci challenged with I. fumosorosea ZVI nanoparticles was both concentration and age dependent. Isaria fumosorosea ZVI nanoparticles showed high pathogenicity against second and third instar nymphs, and pupae with LC₅₀ values of 19.17, 26.10 and 37.71 ppm, respectively. The LT₅₀ was lowest for second instar nymphs (3.15 days) and highest for pupae (4.22 days) when inoculated with a concentration of 50 ppm.

CONCLUSION

Isaria fumosorosea ZVI nanoparticles can be an eco-friendly tool for effective B. tabaci management. © 2019 Society of Chemical Industry.

Bioactivity of an oxymatrine-based commercial formulation against Brevipalpus yothersi Baker and its effects on predatory mites in citrus groves

The acaricidal bioactivity of an oxymatrine-based commercial formulation against Brevipalpus yothersi Baker (Acari: Tenuipalpidae), a vector mite of the Citrus leprosis virus (CiLV), and its impact on predatory mites were assessed. For this purpose, laboratory and field assays using bioacaricide concentrations ranging from 0.5 to 2.0 mg L^-1 of oxymatrine were performed during the years from 2015 to 2016. Laboratory results showed that the oxymatrine-based commercial formulation does not cause deleterious effects on B. yothersi eggs; however, it causes high larval mortality. For adult females, the bioacaricide caused high acute toxicity and residual effect for at least 5 days after application. In the field, the bioacaricide exhibited high acaricidal activity against B. yothersi, with efficacy levels similar to that of synthetic acaricide spirodiclofen (48 mg L^-1) until 49 days after the application. The application of the bioacaricide did not negatively affect the population levels of phytoseiid predatory mites. Therefore, our results suggest that the oxymatrine-based commercial formulation is an important tool for management of the citrus leprosis mite in citrus groves.

Expression of spider toxin in entomopathogenic fungus Lecanicillium muscarium and selection of the strain showing efficient secretion of the recombinant protein

Beta/delta-agatoxin-1 of spider Agelena orientalis was expressed in entomopathogenic fungus Lecanicillium muscarium. To ensure secretion of the recombinant product by the fungus, the signal secretory peptide of the Metarhizium anisopliae Mcl1 protein was inserted into the sequence. For detection of the recombinant product and selection of transformants, the toxin sequence was also fused with eGFP at the C-terminus. The gene encoding the A. orientalis toxin with the Mcl1 protein signal peptide was commercially synthesized, amplified and cloned into the vector pBARGPE1 designed for heterologous expression under the control of the PgpdA promoter and the trpC terminator of Aspergillus nidulans. A double selection on selective medium and microscopic analysis of transformants allowed obtaining a mitotically stable recombinant strain of L. muscarium. The recognition of the Mcl1 derived signal peptide in the cells of transformants and effective secretion of the hybrid product was confirmed by immunoblotting.

Changes in antifungal defence systems during the intermoult period in the Colorado potato beetle

Susceptibility to the fungus Metarhizium robertsii and changes in host defences were evaluated in different stages of the intermoult period (4-6 h, 34-36 h and 84-86 h post moult in IV larval instars) of the Colorado potato beetle. A significant thickening of the cuticle during larval growth was accompanied by decreases in cuticle melanization, phenoloxidase activity and epicuticular hydrocarbon contents (C28-C32). At the same time, a decrease in the conidial adhesion rate and an increase in resistance to the fungus were observed. In addition, we recorded significant elevation of the encapsulation rate and total haemocyte counts in the haemolymph during the specified period. The activity of detoxification enzymes decreased in the haemolymph but increased in the fat body during larval growth. No significant differences in the fatty acid content in the epicuticle were observed. The role of developmental disorders in susceptibility to entomopathogenic fungi is also discussed.

Identification and Virulence Characterization of Two Akanthomyces attenuatus Isolates Against Megalurothrips usitatus (Thysanoptera: Thripidae)

Megalurothrips usitatus (Bagnall) is one of the most harmful pests of leguminous plants. In order to expand our knowledge on the infection of M. usitatus by entomopathogenic fungi, two newly identified isolates of Akanthomyces attenuatus (Zare & Gams) were tested for their pathogenicity against M. usitatus. Both isolates of A. attenuatus (SCAUDCL-38 and SCAUDCL-56) were isolated from soil and were identified by morphological and molecular analyses. The adult females of M. usitatus were treated with five different concentrations (1 × 104, 1 × 105, 1 × 106, 1 × 107, and 1 × 108 conidia/mL) of the isolates. Our results revealed 76.25% and 57.5% mortality of M. usitatus after five days of treatment with 1 × 108 conidia/mL of SCAUDCL-38 and SCAUDCL-56, respectively. The median lethal concentrations (LC50) of SCAUDCL-38 and SCAUDCL-56 calculated through linear regression analysis after five days of fungal treatment of M. usitatus were 1.9 × 106 and 1.5 × 107 conidia/mL, respectively, whereas the median lethal time (LT50) observed for 1 × 108 conidia/mL of SCAUDCL-38 and SCAUDCL-56 were 3.52 days and 4.9 days, respectively. A. attenuatus isolates SCAUDCL-38 and SCAUDCL-56 are highly pathogenic strains of M. usitatus. These findings offer valuable information on the development and commercialization of alternative control measures against M. usitatus.

Degradative properties of two newly isolated strains of the ascomycetes Fusarium oxysporum and Lecanicillium aphanocladii

Two ascomycete strains were isolated from creosote-contaminated railway sleeper wood. By using a polyphasic approach combining morpho-physiological observations of colonies with molecular tools, the strains were identified as Fusarium oxysporum Schltdl. (IBPPM 543, MUT 4558; GenBank accession no. MG593980) and Lecanicillium aphanocladii Zare & W. Gams (IBPPM 542, MUT 242; GenBank accession no. MG593981). Both strains degraded hazardous pollutants, including polycyclic aromatic hydrocarbons, anthraquinone-type dyes, and oil. Oil was better degraded by F. oxysporum, but the aromatic compounds were better degraded by L. aphanocladii. With both strains, the degradation products of anthracene, phenanthrene, and fluorene were 9,10-anthraquinone, 9,10-phenanthrenequinone, and 9-fluorenone, respectively. During pollutant degradation, F. oxysporum and L. aphanocladii produced an emulsifying compound(s). Both fungi produced extracellular Mn-peroxidases, enzymes possibly involved in the fungal degradation of the pollutants. This is the first report on the ability of L. aphanocladii to degrade four-ring PAHs, anthraquinone-type dyes, and oil, with the simultaneous production of an extracellular Mn-peroxidase.

Synthesis, characterization and in vitro biological evaluation of two matrine derivatives

Matrine is a traditional Chinese medicine and botanical pesticide with broad biological activities, including pharmacological and agricultural activities. In present work, two matrine derivatives have been successfully synthesized via introducing indole and cyclohexylamino to 13 position of matrine, respectively, with sophocarpine as starting material, and structurally characterized via infrared spectroscopy(IR), MS, 1 H NMR, 13 C NMR and X-ray crystal diffraction. The results of the in vitro biological activity tests showed that these two matrine derivatives exhibited even better activities against human cancer cells Hela229 and insect cell line Sf9 from Spodoptera frugiperda (J. E. Smith) than that of parent matrine, suggesting that the heterocyclic or cyclic group can dramatically increase the biological activity of matrine. It is worth to mention that 13-indole-matrine could possibly inhibit the growth of insect cells or human cancer cells by inducing cell apoptosis. The results of the present study provide useful information for further structural modifications of these compounds and for exploring new, potent anti-cancer agents and environment friendly pesticides.

Safety of Natural Insecticides: Toxic Effects on Experimental Animals

Long-term application and extensive use of synthetic insecticides have resulted in accumulating their residues in food, milk, water, and soil and cause adverse health effects to human and ecosystems. Therefore, application of natural insecticides in agriculture and public health sectors has been increased as alternative to synthetic insecticides. The question here is, are all natural insecticides safe. Therefore, the review presented here focuses on the safety of natural insecticides. Natural insecticides contain chemical, mineral, and biological materials and some products are available commercially, e.g., pyrethrum, neem, spinosad, rotenone, abamectin, Bacillus thuringiensis (Bt), garlic, cinnamon, pepper, and essential oil products. It can induce hepatotoxicity, renal toxicity, hematotoxicity, reproductive toxicity, neurotoxicity, and oxidative stress. It can induce mutagenicity, genotoxicity, and carcinogenicity in mammals. Some natural insecticides and active compounds from essential oils are classified in categories Ib (Highly hazardous) to U (unlikely toxic). Therefore, the selectivity and safety of natural insecticides not absolute and some natural compounds are toxic and induce adverse effects to experimental animals. In concussion, all natural insecticides are not safe and the term "natural" does not mean that compounds are safe. In this respect, the term "natural" is not synonymous with "organic" and not all-natural insecticide products are acceptable in organic farmers.

Synergistic and additive interactions of Serratia marcescens S-JS1 to the chemical insecticides for controlling Nilaparvata lugens (Hemiptera: Delphacidae)

The combined use of entomopathogens and chemical agents has been suggested as an alternative strategy to control pest insects. However, the effectiveness of combinations of entomopathogenic bacteria and insecticides against rice planthoppers is largely unknown. Here, we evaluated the separate and combined effects of an entomopathogenic bacterium, Serratia marcescens S-JS1, and spirotetramat or thiamethoxam insecticides against third-instar nymphs of Nilaparvata lugens Stål (Hemiptera: Delphacidae) under laboratory and greenhouse conditions. Under laboratory conditions, the combinations caused higher mortality in the third-instar nymphs of N. lugens and produced a synergistic or additive effect compared with the treatments with either bacterial suspension or insecticide alone. Application of S-JS1 (1 × 109 cfu/ml) in combination with 20 mg/liter spirotetramat resulted in 80.5% of N. lugens nymphal mortality, compared with 52.7% in spirotetramat alone treatments, and interactions resulted in a synergistic responses. Other combination treatments of S-JS1 with either insecticide concentration all exhibited additive interactions. In further greenhouse tests, S-JS1 (1 × 109 cfu/ml) + spirotetramat (20 mg/liter) and S-JS1 (1 × 109 cfu/ml) + thiamethoxam (5 mg/liter) showed additive effects against the nymphs, and were found to be most effective relative to their individual treatments on days 5 and 9. Our results indicate that S. marcescens S-JS1 combined with insecticide may provide a promising new strategy for controlling N. lugens.