Emamectin Research Articles

Impact of the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff ) Sorokin on Spodoptera frugiperda (J.E Smith), an invasive maize pest in Chad

The invasion of agricultural plots by Spodoptera frugiperda (J.E Smith) constitutes a serious constraint to the sustainable maize production in Chad. Since then, farmers have unsuccessfully used available chemical insecticides to control this pest at that respect, the present study evaluated the bio-efficacy of two strains (Chinese and Senegalese) of Metarhizium anisopliae on the pest, both under laboratory and field conditions. Laboratory results showed that both strains were virulent against FAW resulting in a mortality of 90 ± 5.77% for the strain from Senegal and 75 ± 5.00% for that from China. In the field, significant differences were observed among the four treatments tested, namely the two M. anisopliae strains (2.5 kg/ha), the control and Emamectin benzoate (20g/ha) for both the infestation of maize plants and FAW densities (P <0.05). Meanwhile, maize grain yields were significantly the highest in plots treated with Emamectin benzoate followed by plots treated with either of the two strains of the fungus whose yields were statistically similar (df = 3; F = 27.13; P <0.0001). This biopesticide was more virulent under laboratory and field conditions and could be a promising biological control agent against S. frugiperda as an alternative to synthetic insecticides. However, additional studies that evaluate the implementation cost of the microbiological control are very necessary for more objective and robust conclusions. Key words: Fall armyworm, microbiological control, Zea mays, Emamectin benzoate, biopesticides.

Side effects of insecticides used for management of Tuta absoluta Meyrick (Lepidoptera: Gelechidae) on the biocontrol agent Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae)

Trichogramma brassicae is one of the most important egg parasitoids of many pests including South American tomato pinworm, Tuta absoluta (Lepidoptera: Gelechiidae). In agrosystems, the function of parasitoids can be affected by the application of insecticides. To use biological control agents and pesticides simultaneously in pest management, it is necessary to know the potential effect of pesticides on biological control agents. In this study, the lethal and sublethal effects of four insecticides (flubendiamide, emamectin benzoate + lufenuron, thiocyclam, and spinosad) frequently used to control T. absoluta, were investigated on its parasitoid Trichogramma Brassicae Bezdenko (Hymenoptera: Trichogrammatidae), under controlled laboratory conditions. The results showed that spinosad with an LC50 value of 0.73 mg a.i./ L was highly toxic against adults of T. brassicae in comparison to flubendiamide (4.09 mg a.i./ L), emamectin benzoate + lufenuron (4.17 mg a.i./ L), and thiocyclam (9.59 mg a.i./ L). Furthermore, key demographic parameters such as net reproductive rate (R0), intrinsic rate of increase (rm), mean generation time (T), and doubling time (DT) were significantly decreased after exposure of T. brassicae to the LC30s of spinosad, thiocyclam, flubendiamide, and emamectin benzoate + lufenuron compared to the control. In the light of our results, the four insecticides should be used cautiously in T. absoluta integrated management programs. While the thiocyclam can be combined with the T. brassicae, the flubendiamide and emamectin benzoate + lufenuron are not recommended in the presence of this parasitoid. The use of spinosad should be avoided concomitantly with the release of T. brassicae.

Combating Spodoptera frugiperda (Lepidoptera: Noctuidae) with Moringa-Synthesized Silica Nanoparticles and Its Combination with Some Insecticides.

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is a major agricultural pest known for developing resistance to insecticides. This study investigated a novel approach to manage FAW by silica nanoparticles (SiNPs) synthesized from eco-friendly leaf extract of Moringa oleifera Lam. (Moringaceae). This green synthesis method offers a sustainable and potentially safer alternative to traditional chemical processes. SiNP formation was confirmed by various techniques: UV-visible spectrophotometer, X-ray spectroscopy with energy-dispersive (EDX), scanning electron microscopy (SEM), and dynamic light scattering (DLS). The effectiveness of SiNPs alone and their combination with three common insecticides (emamectin benzoate, indoxacarb, and chlorpyrifos) were evaluated against third instar larvae of fall armyworm. While SiNPs after 24h by leaf dipping method recorded limited insecticidal activity (LC50 = 9947.59mg/L), it significantly enhanced the potency of all three insecticides. Combining SiNPs with emamectin benzoate resulted in the most dramatic increase in effectiveness compared to the insecticide alone with LC50 = 0.295mg/L and 0.42mg/L, respectively. This research suggests that moringa extract can be a valuable resource for the green synthesis of nanoparticles potentially useful in pest control. This approach could potentially reduce the amount of insecticide needed for effective pest control, leading to a more sustainable and environmentally friendly agricultural practice.

Optimized emamectin benzoate trunk injection: addressing temperature limitations for pine wilt disease control.

Pine wilt disease (PWD), caused by the pinewood nematode Bursaphelenchus xylophilus, poses a significant threat to global forestry, resulting in extensive economic and ecological damage. Traditional trunk injection agents (TIAs) are limited by environmental factors, such as high winter temperatures and vigorous resin flow, particularly in southern China. This study aimed to develop an ordinary temperature trunk injection agent (OTTIA) for year-round application and to evaluate its performance under high-temperature conditions in comparison to commercial TIAs. Extensive laboratory and field tests identified N,N-Dimethylformamide (DMF) and benzyl acetate as optimal solvents and Tween-40 as an effective emulsifier for the OTTIA formulation. The new agent was fully absorbed by Pinus massoniana within 3 h at temperatures exceeding 30 °C, outperforming existing commercial agents. Treated trees maintained comparable emamectin benzoate (EB) levels but achieved lower LC90 lethal concentration values (27.65 mg L-1), indicating greater efficacy. The OTTIA provided protection against PWD for ≤360 days postinjection. The development of OTTIA marks a significant advancement in PWD management, offering an effective solution for high-temperature regions and potentially transforming year-round treatment strategies. The results highlight the critical role of optimizing solvent and emulsifier combinations to enhance the efficacy and application of trunk injection agents, contributing to sustainable forest management and improved protection against PWD. © 2024 Society of Chemical Industry.

Investigation of resistance ratios and resistance mechanisms of Cydia pomonella (L.) (lepidoptera: Tortricidae) populations collected from apple orchards in Isparta (Türkiye) against some insecticides

The codling moth, Cydia pomonella is an important pest that causes significant economic losses in apples and walnuts in the world. The aim of this study was to investigate, for the first time in Türkiye, the resistance status and resistance mechanisms of codling moth, Cydia pomonella against indoxacarb, deltamethrin and emamectin benzoate. All apple orchard populations developed resistance ratios ranging from 3.38 to 22.37-fold to deltamethrin, 5.67–29.87-fold to indoxacarb and 1.46–3.05-fold to emamectin benzoate. The interaction of some synergists triphenyl phosphate (TPP), piperonyl butoxide (PBO) and diethyl maleate (DEM) with indoxacarb and deltamethrin was analyzed in the susceptible, MAREM and Tepeli populations with moderate resistance to indoxacarb and deltamethrin. While indoxacarb + TPP showed a significant synergistic effect only in MAREM population, a significant synergistic effect was observed with indoxacarb + TPP and indoxacarb + PBO in Tepeli population. The activities of detoxifying enzymes [esterase, glutathion –S– transferase (GST) and cytochrome P450 monooxygenase (P450)] studied by biochemical methods showed some variation depending on the population. The results of biochemical analyses showed that esterase and GST enzyme activities of all populations was between 0.51 and 0.94, 0.77 and1.29 mOD min−1mg−1 proteins, respectively. The P450 enzyme activities ranged from 0.53 to 0.78, RFU min−1mg−1 proteins. In addition, the L1014F knockdown mutation (CTT to TTT) corresponding to leucine to phenylalanine amino acid substitution of the voltage-gated sodium channel in Cydia pomonella was determined in MAREM and Tepeli populations. It was determined that while MAREM and Tepeli populations developed moderate resistance, the other populations developed a low level resistance to deltamethrin and indoxacarb. On the other hand, all populations developed a low level resistance to emamectin benzoate. The P450 and esterase enzyme activities were significantly higher in MAREM and Tepeli populations which were resistant to deltamethrin and indoxacarb than the susceptible population. In addition, a Kdr point mutation L1014F was detected in the deltamethrin resistant MAREM and Tepeli populations.

Regional changes of maximum dose insecticide responses in diamondback moth (Lepidoptera: Plutellidae) populations from Georgia and Florida, USA.

Maximum dose bioassays were conducted to assess the efficacy of multiple registered active ingredients for diamondback moth (DBM), Plutella xylostella (L.), control in Georgia and Florida from 2021 to 2023 as a follow-up to an earlier study. Low efficacy (<40% mortality) was recorded for the highest labeled rate of Bacillus thuringiensis var. kurstaki strain ATBS-351 in Georgia, as well as chlorantraniliprole, cyantraniliprole, and cyclaniliprole in Georgia and Florida. The active ingredients with the highest efficacy (>80% mortality) in both states were naled, emamectin benzoate, and spinetoram. Independent analysis of data by state indicated that the efficacy of bifenthrin, chlorantraniliprole, cyantraniliprole, tolfenpyrad, and methomyl was higher in Florida populations than in Georgia populations. In addition, a comparison of these data to a recent DBM maximum dose survey in the same region suggested that these DBM populations have rapidly developed high levels of resistance to cyantraniliprole and cyclaniliprole. This work provides growers in the region with a recent ranking of insecticide efficacy that documents the loss of control for certain active ingredients, which assists pest managers in the planning of ongoing insecticide rotations for DBM resistance management.

The impact of lethal and sub-lethal exposure of emamectin benzoate on populations of Spodoptera litura (Lepidoptera: Noctuidae) under laboratory conditions

Emamectin benzoate is an avermectin bio-insecticide commonly used for managing several insect pests including Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a major polyphagous pest of many cultivated crops. The current study was conducted to evaluate the effects of emamectin benzoate on the fitness of S. litura populations exhibiting differential susceptibility to insecticide. The selection process and all the bioassays were carried out using 6-day-old 2nd instar larvae of S. litura. A field-collected population of S. litura was divided into two groups: one selected with emamectin benzoate for eight generations (EB-Sel) and the other kept unexposed (Unsel-Lab) to insecticide in the laboratory. An increase in resistance ratio from 1.71-fold in the F1 generation to 22.54-fold in the F8 generation of the EB-Sel population was observed compared to the Unsel-Lab (F8) population. The EB-Sel and Unsel-Lab populations were treated with their respective lethal and sub-lethal concentrations which resulted in an extended development period, decreased larval survival, and adult emergence along with increased morphological abnormalities in adults. Significant reductions were observed in both male and female longevity, fecundity, egg hatching, net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ) in EB-Sel and Unsel-Lab populations. Higher concentrations of the insecticide also reduced the relative fitness (Rf) of S. litura larvae, with maximum effect at LC50 of the EB-Sel population where the Rf value was 0.32 compared to the Unsel-Lab population. Both populations have been affected by emamectin benzoate exposure, however, the impact was more pronounced in the EB-Sel population indicating fitness costs. Our results suggested the fitness cost linked to emamectin benzoate resistance in S. litura which might favor managing insecticide resistance by reducing the frequency of resistant alleles by removing selection pressure. Consequently, our research provides significant insights to devise better pest management strategies for S. litura.

Effects of Botanicals and Synthetic of Insecticides on Field Emergence and Crop Establishment in Mungbean [Vigna radiata (L.) Wilzeck

Mungbean, is a drought-resistant, green manure crop and suitable for dry land as a major pulse crop in India. India is the largest producer and consumer of pulses, which improve soil properties, provide nutritious fodder and prevent soil erosion. However, pests like bruchids can destroy 60% of production, necessitating the use of eco-friendly seed protectants. Laboratory studies were conducted at Acharya Narendra Deva University of Agricultural and Technology, Ayodhya, using mungbean seed cv. IPM-2-3. Seeds were mixed with seed protectants and stored in gunny bags. Field emergence and crop establishment were tested and data were analyzed using a Completely Randomized Design with three replications. Seed protectants and insecticides are effective in maintaining field emergence and crop establishment in mungbean. Emamectin benzoate, Sivanto prime and Gorakhmundi powder are the best treatments, with maximum field emergence and minimum establishment influenced by environmental factors. These findings are supported by various studies. Emamectin benzoate and Neemoz gold were found to be effective insecticides for field emergence and crop establishment in mungbean, with the latter recommended for storability and field establishment.

Efficacy of Alternative Insecticides against Dusky Cotton Bug (Oxycarenus laetus) to Improve Yield Losses in Cotton Crops through Residue-based Bioassay

The study evaluates the efficacy of leufenuron, emamectin benzoate, and thiamethoxam against the Dusky Cotton Bug (Oxycarenus laetus Kirby) using residue-based bioassay methods. Key findings indicate that emamectin benzoate showed the highest efficacy with the lowest LC50 value, making it the most potent insecticide among those tested. Leufenuron and thiamethoxam followed, displaying moderate effectiveness. The results highlight the comparative advantages of emamectin benzoate in controlling Dusky Cotton Bug populations, suggesting its potential role in integrated pest management strategies. This study underscores the need for environmentally friendly alternatives to traditional insecticides in mitigating yield losses in cotton production.

Bioassay of Plant-based and Synthetic Insecticides for the Management of Tomato Leaf Miner, Tuta absoluta (Meyrick) in Open-field Conditions in Salyan, Nepal

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), has invaded most parts of Nepal and threatens tomato production. Their management primarily relies on insecticides in Nepal. Market-available and locally-madeplant-based pesticides are not equally effective in managingT. absoluta. Therefore, this study aimed to evaluate the effectiveness of such potential insecticides in managing T. absoluta in open-field conditions. This study was carried out in the Salyan district of Nepal in 2021 and treatments were designed in a randomized complete block design (RCBD)with seven treatments and three replications. All treatments were sprayed at12-dayintervalsfor two times. The treatments used were Emamect in benzoate 5% SC, Imidacloprid 17.8 SL, Jholmol (botanical mixture extract and urine mixture), Chlorantraniliprole 18.5 SC, Spinosad 45 SC, Azadirachtin 300ppm and Control. The results showed that the lowest percentage of leaves and fruit damage was recorded in Chlorantraniliprole 18.5 SC and Spinosad 45 SC sprayed plots. Insecticide efficiency was ranked as Chlorantraniliprole &gt; Spinosad&gt;Ema-mectin Benzoate &gt; Azadirachtin &gt;Imidaclroprid&gt;Jholmol&gt;Control. Marketable yield was obtained highest in Chlorantraniliprole (85.26 t/ha) treated plots followed by Spinosad (79.26 t/ha); both were not significantly different. This study provides an opportunity to select the most suitable and effective pesticides for the management of tomato leaf miners and can be used in integrated pest management strategies as a selective insecticides.

In vitro and Silico Exploration of the Insecticidal Properties of Lavandula multifida L. Essential Oil and its Binary Combinations with Cyantraniliprole and Emamectin benzoate on Spodoptera frugiperda (Lepidoptera: Noctuidae)

Control methods have faced challenges in effectively managing the spread and damage caused by the fall armyworm (FAW), Spodoptera frugiperda, across various crops worldwide, highlighting the need for more sustainable and integrated approaches. This study explored the insecticidal effect of the essential oil (EO) of lavender (LV) (Lavandula multifida L.), cyantraniliprole (CY), and emamectin benzoate (EM) insecticides on FAW larvae. Toxicity, biological, and biochemical assays were employed to elucidate the impact of the two insecticides individually or combined with LV EO. Additionally, in silico molecular docking investigations were performed for eucalyptol (the major component of LV EO) and for CY against the acetylcholine esterase (AChE) enzyme (PDB ID: 6xyu) and cytochrome P450 (PDB ID: 2q6n). EM was the most toxic compound to FAW larvae with an LC50 of 0.0073 mg L−1, followed by CY and LV EO. The chi-square (χ2) test confirmed the synergistic effect of the LV EO/CY combination and the antagonistic effect LV EO/EM combination on FAW larvae. Biological development studies revealed that both LV EO/CY and LV EO/EM combinations impacted the larval and pupal durations. The biochemical assays indicated that the P450-specific activity was activated by LV EO (at LC25), CY (at LC25 & LC50), and their binary combination (at LC25:LC25). In addition, the LV EO/CY combination significantly activated the AChE and GST-specific activity, and the LV EO/CY combination and CY (at LC50) significantly activated α-esterase- specific activity. Molecular docking investigations revealed energy scores (S) of −6.7729 and −7.7644 kcal/mol for eucalyptol and CY, compared to −7.0993 kcal/mol for PDB ID: 6xyu ligand. The current results can serve as baseline data for utilizing the LV EO/CY combination in the integrated pest management (IPM) of FAW.

Sublethal effects of emamectin benzoate on biological characteristics and the expression of vitellogenin (SgVg) and its receptor in Sclerodermusguani

Emamectin benzoate (EMB) is a commonly used insecticide for controlling agricultural and forest pests. To facilitate its rational use in integrated pest management (IPM), the sublethal effects of EMB on the development and reproduction of Scleroderma guani were evaluated. Sublethal doses of EMB (LD10 and LD30) significantly reduced the longevity and fecundity of F0 females. In the F1 generation, sublethal doses significantly reduced larval development duration and male longevity but significantly extended female longevity. Additionally, the LD30 treatment significantly decreased the number of laid eggs in F1 females by 20.72% compared with the control group. The net reproductive rate (R0) was significantly declined by the LD30 treatment compared with the control group (CK). Furthermore, the mean generation time (T) was significantly extended in both LD10 and LD30 treatment groups. Compared to the control group, the expression of SgVg and SgVgR genes in the LD10 and LD30 groups was significantly lower, which may be a crucial factor for the reduced fecundity of the females. These results indicate that sublethal doses of EMB significantly reduced adult longevity and fecundity of S. guani. The findings are practical for developing IPM strategies for forestry pests using S. guani and EMB.

Efficacy of Certain Bio-Pesticides against the Major Insect Pests of Broccoli (Brassica oleracea var. italica L.)

The field experiment was undertaken at the Experimental Farm, Department of Entomology, School of Agricultural Sciences (SAS), Medziphema Campus, Nagaland University, during the period of November 2021 to February 2022 to study the efficacy of certain bio-pesticides against major insect pests of broccoli. The experiment was conducted using Randomized Block Design (RBD) with six treatments including control and replicated four times. The study revealed that Indian cabbage white, Pieris spp. and green peach aphid, Myzus persicae have been found to be the major insect pest in broccoli. It is recorded that the highest (73.49%) population reduction of M. persicae was obtained from the plot treated with emamectin benzoate 5% SG and the highest (90.16%) population reduction of Pieris spp. was recorded on the plot treated with spinosad 45% SG. Therefore, the study concluded that use of bio-pesticides offers a great efficacy in controlling the pest and diminish the pesticides related issue.

Efficacy of new molecule of insecticide, Emamectin benzoate against polyphagous pest, Helicoverpa armigera (Hubner): A review

Efficacy of new molecule of insecticide, Emamectin benzoate against polyphagous pest, Helicoverpa armigera (Hubner): A review

Validation of LCMS/MS based method for residual estimation of tolfenpyrad and emamectin benzoate in brinjal and cauliflower and their risk assessment

Dissipation and risk assessment of tolfenpyrad and emamectin benzoate was carried out on brinjal and cauliflower after two applications of combination formulation of Tolfenpyrad 18.75 % + Emamectin benzoate 0.94 % w/w SC@ 7.0 (x) and 8.75 (1.25x) g a.i. ha−1. Rapid multi-residue analytical methodology for triple-quadrupole mass spectrometric analysis (LC-MS/MS) was validated to be linear, specific, accurate with acceptable matrix effects, recovery, uncertainty with limit of detection (LOD) of 0.003 mg kg−1and limit of quantification (LOQ) of 0.01 mg kg−1 for both tolfenpyrad and emamectin benzoate. Field experiment revealed that initial deposits of tolfenpyrad were 0.15 and 0.22 mg kg−1in brinjal and 0.54 and 0.85 mg kg−1 in cauliflower head, at x and 1.25 x dose, respectively that reached below LOQ at 10 days in brinjal (both doses) and 5 and 7 days in cauliflower, in x and 1.25 x dose, respectively. Dissipation of tolfenpyrad followed first-order kinetics with DT50 of 0.59 and 0.54 days in brinjal and 0.36 and 0.34 in cauliflower, at respective doses. The initial deposits of emamectin benzoate were below LOQ in brinjal, while in cauliflower the initial deposits were 0.01 and 0.02 mg kg−1 at x and 1.25 x dose, respectively that reached below LOQ at 1 day in both the dosages. Dietary risk assessment in children and adults under rural and urban conditions showed that recommended dosages of tolfenpyrad and emamectin benzoate do not pose any dietary risks to the consumers.

Sublethal effect of emamectin benzoate on age-stage, two-sex life table and population projection of red palm weevil, Rhynchophorus ferrugineus

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, is a devastating insect-pest of 29 plants including date palm. It feeds inside the tree bark thus it is difficult to manage using insecticides. Only a few insecticides have been found effective against RPW. Among these insecticide, emamectin benzoate (EMB) is widely used. This insecticide can pose threat human and environmental health as it is used in the form of tree injection. Thus, keeping in view its possible, its sublethal effect on RPW was studied using Age-stage, two sex life table. Life table parameters of the progeny of exposed larvae to LC10, LC25, and LC50 of EMB were computed. Statistically higher fecundity (161.12 per female) was observed in control treatment, while less fecundity was observed in LC50 treatment. Significantly higher values for intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (Ro) (0.0376, 1.0383, and 67.13 per day, respectively) were recorded for the control treatment. Contrarily, lower values for r, Ro, and λ i.e. 0.0318, 23.82, and 1.0324 per day, respectively were recorded in the LC50 treatment. Decreased population parameters suggest that EMB can be successfully used in for the management of RPW.

F116I mutation in CYP9A25 associated with resistance to emamectin benzoate in Spodoptera litura.

The F116V mutation in the substrate recognition site 1 (SRS1) of Spodoptera exigua CYP9A186 has been demonstrated to confer ~200-fold resistance to emamectin benzoate (EB). In this study, a novel mutation (F116I) in CYP9A25, orthologous to CYP9A186, was detected in a field population of Spodoptera litura (YJ22) collected from Yuanjiang, Yunnan province, China in 2022. The association of this mutation with EB resistance was investigated. Two homozygous strains, YJ22-116F (wild-type at 116 position of CYP9A25) and YJ22-116I (mutant) were isolated from YJ22 through two rounds of crossing and DNA genotyping. Compared with YJ22-116F, the mutant strain YJ22-116I exhibited 31.8-fold resistance to EB. Resistance in YJ22-116I was shown to be incompletely dominant, and genetically linked with the F116I mutation. Further, heterologous expression and in vitro metabolism assays confirmed that the recombinant CYP9A25 protein with 116I mutation obtained metabolic capability against EB, whereas the wild-type CYP9A25 protein (with 116F) did not metabolize EB. Molecular modeling showed that the F116I mutation within SRS1 reduces the steric hindrance to substrate entry and improves ligand-binding interactions. The causal association between the F116I mutation in CYP9A25 and medium-level EB resistance in S. litura has been verified. This finding is critical for the field monitoring of such mutations and thus for developing adaptive resistance management tactics for field populations of S. litura. © 2024 Society of Chemical Industry.

Characterization of ATP-binding cassette transporters associated with emamectin benzoate tolerance: from the model insect Drosophila melanogaster to the agricultural pest Spodoptera frugiperda.

Multiple families of detoxification genes, including the increasingly recognized family of ATP-binding cassette (ABC) transporters, work together to influence the toxicity of synthetic insecticides and thus their resistance. Effective management of insecticide resistance requires identification of all toxicity-affecting members from each family of toxicity-related genes. Here, we used emamectin benzoate (EB), ABC transporters and Spodoptera frugiperda as a working case to test whether the strategy of 'from the model insect Drosophila melanogaster to agricultural pests' can identify all or most ABC transporter members related to EB tolerance in S. frugiperda. After confirming the involvement of ABC transporters in the toxicity of EB against fruit fly with the ABC inhibitor verapamil, four ABC transporter genes (DmCG3327, DmCG11147, DmCG4822, and DmCG7627) were found to be involved in EB tolerance using RNA interference-based family-wide functional screening. A combination of phylogenic analysis and a reciprocal TBLASTN search identified five S. frugiperda ABC transporter members as homologs (SfABCC4, SfABCG1, and SfABCG23) or one-way best hits (SfABCG4 and SfABCG20) of the four fly ABC genes. Real-time quantitative polymerase chain reaction (qPCR) analysis found that all five S. frugiperda ABC transporter genes were inducible by EB, and expressed in all the developmental stages and larval tissues, but with significant quantitative differences among stages and tissues. A cytotoxicity assay of ABC-overexpressing Sf9 cell lines showed that all the five S. frugiperda ABC transporter genes made Sf9 cells tolerant to EB. This study not only identifies nine ABC transporter genes related to EB tolerance from D. melanogaster (four genes) and S. frugiperda (five genes), but also demonstrates the utility and effectiveness of the 'model to pests' strategy to identify most toxicity-affecting members from a given family of toxicity-related genes. © 2024 Society of Chemical Industry.

Chlorantraniliprole resistance associated with diamondback moth (Lepidoptera: Plutellidae) outbreaks in Arizona Brassica crops.

The diamondback moth, Plutella xylostella (Linnaeus), isone of the most important insect pests of Brassica crops worldwide. In October 2016, outbreaks of an invasive P. xylostella population and unexpected control failures occurred on broccoli and cauliflower crops throughout all vegetable-growing regions in Arizona. Nineteen populations of Plutella xylostella were collected from 2016 to 2021 from various commercial cauliflower fields in Yuma and Scottsdale, Arizona, and from experimental broccoli plots at the University of Arizona, Yuma Agricultural Center (UAYAC), Yuma, Arizona. Populations collected from the commercial cauliflower fields had been transplanted with seedlings produced in a local Yuma nursery in 2016 and Salinas, CA in 2017 to 2018, whereas experimental broccoli plots were direct seeded. These populations were evaluated for their susceptibility to chlorantraniliprole, spinetoram, emamectin benzoate, and cyantraniliprole. In this study, field rate laboratory bioassays, serial dilution laboratory bioassays, and field efficacy spray experiments were performed. The field rate laboratory bioassay results showed that spinetoram, emamectin benzoate, and cyantraniliprole remained effective at controlling P. xylostella, but chlorantraniliprole did not control P. xylostella at the field rate. Additionally, serial dilution bioassays confirmed significant levels of cyantraniliprole and chlorantraniliprole resistance in the P. xylostella populations collected from transplanted cauliflower fields. However, the results of the multiyear/growing-seasons study monitoring the susceptibility of P. xylostella populations collected from direct-seeded broccoli and field efficacy trials conducted at the UAYAC indicated that the resistance to diamide insecticides was neither uniform nor persistent following the 2016 outbreak. Nevertheless, the risk for P. xylostella resistance in Arizona vegetable-growing regions exists, particularly in Brassica transplants. Therefore, we recommend that Arizona Brassica growers remain vigilant and practice rigorous insecticide resistance management to offset the development of resistance.

Molecular characterization and functional analysis of genes mediating emamectin benzoate action to the pinewood nematode (Bursaphelenchus xylophilus)

Emamectin benzoate (EB) is a highly effective and low-toxicity pesticide for the control of Bursaphelenchus xylophilus. However, its action mechanism in B. xylophilus has not yet been verified. Here, the genes (Bxy-glc-1, Bxy-glc-2, Bxy-glc-4, and Bxy-avr-14) encoding the glutamate-gated chloride channel (GluCl) of B. xylophilus were analysed and cloned. Functional validation of the target genes was conducted using RNAi and pathogenicity detection assays. The results of the bioinformatics analysis showed that the four GluCl genes contained the Cys-loop region and three transmembrane structural domains. Molecular docking and molecular dynamics simulation predictions revealed that BXY-GLC-2, BXY-GLC-4, and BXY-GLC-1 all had strong binding affinities to EB, and BXY-AVR-14 had no binding affinity to EB. The expression and in situ hybridisation of Bxy-glc-1, Bxy-glc-2, Bxy-glc-4, and Bxy-avr-14 was significantly higher in adult B. xylophilus than at other developmental stages. Interference of Bxy-glc-1, Bxy-glc-2, and Bxy-glc-4 significantly reduced adult mortality relative to the control group, and interference of Bxy-avr-14 did not have a significant on adult mortality. Adult mortality was lowest in the combined Bxy-glc-2 + Bxy-glc-4 treatment group, followed by the Bxy-glc-1 + Bxy-glc-2 and Bxy-glc-1 + Bxy-glc-4 groups. No significant changes were observed in the mortality rate of the Bxy-avr-14 group and the combination of the other three genes. The dsBxy-glc-1, dsBxy-glc-2, and dsBxy-glc-4 groups accelerated the progression of pine wilt disease induced by EB relative to the sole EB-treated group. Our results confirmed that Bxy-glc-1, Bxy-glc-2, and Bxy-glc-4 are target genes of GluCl in B. xylophilus.