Control Of Spodoptera Frugiperda Research Articles

Eco-friendly O-carboxymethyl chitosan base chlorfenapyr nanopesticide for effective pest control and reduced toxicity to honey bees

Enhancing pesticide selectivity is one of the important strategies to improve pesticide utilization and protect non-target organisms. Herein, a pH-controlled release carrier was prepared to enhance insecticidal activity and reduce toxicity to bees by polysaccharide materials O-carboxymethyl chitosan (O-CMCS) and crosslinker‑sodium tripolyphosphate (TPP). Chlorfenapyr (CF) was encapsulated through crosslinking and self-assembled to form a stable nanopesticide (CF@O-CMCS) with a loading ratio of 5.27 %. CF@O-CMCS had excellent pH release dependency. In 36 h, only 26.39 % of the CF in the CF@O-CMCS was released at pH 5.0, whereas 95.28 % was released at pH 10.0. Treated for 48 h with 2.5 mg.ai/L, CF@O-CMCS was 73.33 % more effective at controlling Spodoptera frugiperda larvae than CF SC (Suspension), which was only 40.00 % effective. The lethal concentration 50 % (LC50) of 11.41 mg/L in CF@O-CMCS was four times lower than that of 2.71 mg/L in CF SC at 96 h, making it safer for worker bees. Additionally, CF@O-CMCS treated the gut of worker bees had considerably lower contents of chlorfenapyr and tralopyril (1.13 and 0.59 mg/kg) than CF SC (3.22 and 1.91 mg/kg) group. In consideration of its eco-friendly, enhanced bioactivity, and low toxicity to worker bees, CF@O-CMCS will have a broad application prospect in sustainable agriculture.

Cyclosporin A as a Source for a Novel Insecticidal Product for Controlling Spodoptera frugiperda.

The fall armyworm (FAW), Spodoptera frugiperda, causes substantial annual agricultural production losses worldwide due to its resistance to many insecticides. Therefore, new insecticides are urgently needed to more effectively control FAW. Cyclosporin A (CsA) is a secondary metabolite of fungi; little is known about its insecticidal activity, especially for the control of FAW. In this study, we demonstrate that CsA shows excellent insecticidal activity (LC50 = 9.69 μg/g) against FAW through significant suppression of calcineurin (CaN) activity, which is a new target for pest control. Combinations of CsA and indoxacarb, emamectin benzoate, or Vip3Aa showed independent or synergistic toxicity against FAW; however, the combination of CsA and chlorantraniliprole showed no toxicity. Sublethal doses of CsA led to decreases in FAW larval and pupal weight, pupation, emergence, mating rates, adult longevity, extended development of FAW larvae and pupae and the pre-oviposition period of adults, and increases in the proportion of pupal malformation. Importantly, CsA treatment reduced FAW ovarian size and female fecundity, which suggests that it has great potential to suppress FAW colony formation. Taken together, these results indicate that CsA has high potential as an insecticide for controlling FAW.

Effectiveness of Neem Oil and Jatropha Oil in Controlling Spodoptera frugiperda (J.E Smith) on Maize in the Republic of Chad

Upon the evidence of its invasion in Chad in 2018, Spodoptera frugiperda has become a serious threat to maize production, thereby prompting farmers to a massive use of chemical pesticides to reduce its damage. However, given the adverse negative effects of chemical pesticides on human health and the environment, alternatives to chemical control are highly sought. In that respect, the effectiveness of Neem oil and Jatropha oil, two bio pesticides widely acknowledged for their insecticidal properties, was evaluated in the field in comparison with the chemical insecticide, Emamectin benzoate, in a Fisher Blocks design with 4 treatments and 4 replicates. The mean larval density per 25 plants was significantly the lowest (P < 0.0001) on Emamectin benzoate-treated plants(1.13 ± 0.70), followed by Jatropha oil (6.13 ± 0.87) and Neem oil treatments (7.13 ± 0.80) while the highest density was recorded on the untreated plants (12.31 ± 0.87). Similarly, the infestation rates were significantly lower on plots that received the chemical insecticide or the bio pesticides compared to the control plots (P < 0.0001). Foliar and ear damage scores were also significantly lower on the treated than on the control plots (P < 0.0001); and the number of ears attacked was significantly higher on the untreated control than on the other treatments. Maize grain yields were significantly higher in the treated plots compared to the control plots (P < 0.001). Yield gains over the control were 132.57%, 90.91% and 72.73% respectively for Emamectin benzoate, Jatropha oil and Neem oil treatments. It appears, therefore, that the use of Jatropha oil or Neem oil could significantly contribute to an effective and sustainable management of S. frugiperda on maize in Chad, thereby calling for the need for further investigations in that area in the frame of integrated pest management of this pest.

PH/redox/α-amylase triple responsive metal-organic framework composites for pest management and plant growth promotion

The development of stimuli-responsive controlled release formulations is a promising strategy to enhance the utilization efficiency and reduce the environmental pollution of pesticides. In this work, a smart pH/redox/α-amylase triple stimuli-responsive pesticide delivery system was constructed by bonding carboxymethyl starch (CMS) with metal-organic frameworks (MIL-101(Fe)–NH2 nanoparticles) which loaded with CAR (CAR@MIL-101(Fe)-CMS nanoparticles). The results indicated that the loading capacity of CAR@MIL-101(Fe)-CMS nanoparticles for CAR was approximately 18.3% and the CMS attached on the surface of CAR@MIL-101(Fe)–NH2 nanoparticles could protect CAR from photolysis effectively. Meanwhile, the coated CMS and metal-organic framework structure of the nanoparticles could be decomposed and consequently release pesticide active ingredients on demand when CAR@MIL-101(Fe)-CMS nanoparticles were metabolized by glutathione and α-amylase in the insect alkaline midgut. The bioactivity survey confirmed that CAR@MIL-101(Fe)-CMS nanoparticles had a longer duration in controlling Spodoptera frugiperda larvae compared to CAR suspension concentrate. In addition, the MIL-101(Fe)-CMS nanocarriers were safe for the growth of maize and could be used as fertilizer to promote the growth and development of crops. Thus, this smart stimuli-responsive pesticide-fertilizer all-in-one combination strategy has great potential in pest management.

Preparation and characterization of emamectin benzoate nanocapsules based on the dual role of polydopamine.

Developing pesticide-controlled release formulations with foliage adhesion has become the focus of current research in the field of crop protection. In this study, an excellent adhesive nanocapsule loaded with emamectin benzoate (Eb@PDA) was prepared via emulsion interfacial polymerization based on the self-polymerization ability and adhesion properties of polydopamine (PDA). The physicochemical properties of the Eb@PDA were characterized by scanning electron microscopy, transmission electron microscopy, particle size statistics, Fourier transform infrared spectroscopy and X-ray diffraction. The Eb@PDA presented a regular spherical shape, with an average particle size of 163.8 nm. Compared with conventional formulations, it had higher pesticide-loading content (34%) and excellent adhesion onto corn leaf. In addition, Eb@PDA showed sustained-release characteristics, facilitating the release of Eb at low pH and high temperature. Eb@PDA could effectively protect Eb against photodegradation and had a longer effective period for controlling Spodoptera frugiperda and Spodoptera exigua. Furthermore, acute toxicity tests showed that the 50% lethal concentration (LC50 ) was 80.91 and 57.91 mg kg-1 at 7 and 14 days, respectively, indicating a lower toxicity of the Eb@PDA to earthworms. The cells (L02) treated with Eb@PDA showed a higher cell viability but a lower apoptosis rate (only 5.75%), demonstrating the lower cytotoxicity of the Eb@PDA. The self-prepared Eb@PDA could be used as a formulation with the advantages of slow release, UV shielding, strong leaf adhesion, superior insecticidal properties, sustained effectiveness and biosafety. It will also facilitate the development of an efficient and safe pesticide delivery system. © 2022 Society of Chemical Industry.

Efficacy of Insecticides Applied to Soybean Seeds for Controlling Lepidoptera Caterpillars

The use of high-quality seeds is essential for the crop to express its full potential. The application of seed treatment constitutes a widely spread operation, every year new products are discovered and used for seed treatment, which can provide a protective effect against pests that attack the seeds, as well as physiological effects to favor the growth and initial development of plants, however, little is known about the influence of insecticides on seed germination and the emergence of soybean seedlings. The experiment was carried out in the Seed Quality Analysis Laboratory and in the experimental field of the Agrarian Sciences Faculty of the National University of Asunción-Paraguay. The objective consisted of evaluating the efficacy of chemical insecticides applied to soybean seeds to control lepidopteran caterpillars during the implantation of the crop, and the effect on the germination of seeds in the laboratory and the emergence in the field. Commercial soybean seeds were used and the treatments were the following (in cc of c.p./100 kg seeds): control (without treatment), thiamethoxam (200), cyantraniliprole + thiamethoxam (200), thiamethoxam + lambda-cyhalothrin (200), imidacloprid (400), imidacloprid + thiodicarb (500) and fipronil (200). The variables evaluated were: germination under laboratory conditions, number of larvae presented at 14, 21 and 28 days after emergence, seedling emergence and efficacy of chemical products in the field. The design used in the field was complete block to the random and in laboratory fully randomized, with seven treatments and 4 replications with a total of 28 experimental units for both trials. The data obtained were compared through the analysis of variance using the statistical software SASM-Agri and those variables that presented significant statistical differences between the means of the treatments were compared using the Scott-Knott test at 5% probability, while efficacy was determined by the Abbot formula. The data show that the chemical insecticides did not affect the germination of seeds in the doses tested. The highest percentages of emergence in the field were obtained with the insecticides thiamethoxam, cyantraniliprole + thiamethoxam, imidacloprid and imidacloprid + thiodicarb. At 28 day after seedling emergence the active ingredients cyantraniliprole + thiamethoxam and imidacloprid + thiodicarb achieved the greatest reduction in the lepidoptera population. Seed treatment with the active ingredients used in this study is an effective practice for the control of Spodoptera frugiperda, Spodoptera cosmioides and Agrotis ipsilon caterpillars during the initial stage of soybean cultivation.

Bioassays of Beauveria bassiana Isolates against the Fall Armyworm, Spodoptera frugiperda.

The control of Spodoptera frugiperda, the key invasive pest of maize, is a serious concern due to its biology and the current global restriction on applying synthetic pesticides. Entomopathogenic fungi are considered to be a potential biological control strategy. The pathogenicity of 12 isolates of Beauveria bassiana in the immature stages and feeding efficacy of S. frugiperda were evaluated. The B. bassiana isolates QB-3.45, QB-3.46 and QB-3.428 caused the highest egg mortality rates of 87.3, 82.7 and 79.3%, respectively, when applied at a concentration of 1 × 108 conidia/mL and measured at 7 days post-treatment. Neonate mortality rates of 45.6 to 53.6% were observed with the same isolates. The B. bassiana isolates caused significant cumulative mortality rates ranging from 71.3 to 93.3% at 14 days post-treatment and reduced larval feeding efficacy from 69.4 to 77.8% at 48 h post-treatment. This study supports using the effective B. bassiana isolates as a biological control agent against S. frugiperda. The significant mortality of the eggs and neonatal larvae and the reduction in the feeding efficacy of the second instar larvae of the S. frugiperda that were treated with isolates of B. bassiana supports the application of entomopathogenic fungi as a biocontrol agent for the effective control of the S. frugiperda population.

Assessment of Pull- and Push Technologies in Managing Spodoptera frugiperda in Maize and Multivariate Analysis of Associated Variables

Aims: The effect of push and pull technology in controlling Spodoptera frugiperda in maize may vary depending on environment understudy and the cereal- legume combination treatment employed. The objectives of this study were therefore, to; i) assess the effectiveness of push-pull technologies in controlling Spodoptera frugiperda infestation in maize ii) cluster the technologies into distinct sets, and iii) identify the variables with high discriminating influence among clustered push-pull technology sets.
 Place and Duration of Study: The research was undertaken in Chilanga district, Zambia during the 2021/ 22 cropping season.
 Methodology: The experiment was laid as a randomised complete block design (RCBD) with three replications and 6 treatments. Four push –pull combinations and the two controls (Negative and Positive). Maize was used as a test crop. Data on Spodoptera frugiperda incidence was collected at weekly intervals for a period of 5 weeks and at harvest from maize crop. Analysis on measured variables was computed using analysis of variance (ANOVA) and principle component analysis (PCA), a multivariate tool.
 Results: Significant differences were obtained on all measured variables except harvest index with regards to push- pull treatments main effects (P =0.05). The evaluation of treatments using principal component analysis showed that push - pull treatments clustered into four sets, arising from a phenotypic variation explained of 89.1%.
 Conclusion: This study revealed Pearl millet/ Marigold push-pull treatment as the best performing treatment with a mean maize test yield value of 7.2 tons per hectare. For variables: number of damaged leaves, injury score leaves, egg batch, biomass with cobs, shelling %, plant height and grain yield were identified as important at differentiating the performance of push pull technologies.

Optimization of In Vivo Production of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV).

Insect viruses have been used to protect crops and forests worldwide for decades. Among insect viruses, isolates of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) have proven potential for the control of Spodoptera frugiperda (J. E. Smith) (FAW)(Lepidoptera: Noctuidae), a pest of many economically essential crops across several continents. Mass production of SfMNPV depends on an in vivo system using host insect rearing. However, many factors can limit its production, including abiotic factors and host characteristics, such as the stage of development and an antagonist intraspecific interaction. Thus, to improve in vivo production, we verified the most suitable larval age to inoculate the virus and the influence of incubation temperature on viral production. Subsequently, cannibal behavior was verified in FAW larvae reared at different densities, while reproducing the conditions of the best treatments. The highest viral yield occurred when FAW larvae were inoculated at 10 and 8days old and incubated at 22°C and 25°C, respectively. Nonetheless, survival (lethal period in days) and cannibal behavior were positively influenced by larval development, which potentially increases the load of contamination and requires larval individualization for these production conditions. In contrast, 4-day-old larvae, which were inoculated and incubated at 31°C, also demonstrated high viral production, with lower rates of cannibalism and death on the same day, thereby showing potential. The information presented in this study is useful for the optimization of the in vivo production systems of SfMNPV.

Efficiency of Three Egg Parasitoid Species on Fall Armyworm (Lepidoptera: Noctuidae) in Laboratory and Field Cages

Abstract Egg parasitoids are the most used natural enemies in biological control of Spodoptera frugiperda (J.E. Smith), a pest of gramineous plants native to the Americas that recently invaded Africa and some countries of Asia. Although Trichogramma pretiosum (Riley) is one of the main species used against this pest, there are other species with equal or greater parasitism potential. The objective of this work was to compare, in laboratory and in field cages, the parasitism of Telenomus remus Nixon, Trichogramma atopovirilia (Oatman and Platner), and T. pretiosum on S. frugiperda eggs. Telenomus remus and T. atopovirilia reached the highest percentages of parasitism in laboratory (>70%) which did not differ statistically from each other. Trichogramma pretiosum had the lowest percentage of parasitism (29%) of the three. In the field cage assays, Te. remus parasitized 30% of the S. frugiperda egg masses, and T. pretiosum parasitized about 7.5% of the egg masses. These results underscore the importance of adequate selection of egg parasitoids for their use in biological control programs by augmentation against S. frugiperda.

Comparative Genomics Sheds Light on the Convergent Evolution of Miniaturized Wasps.

Miniaturization has occurred in many animal lineages, including insects and vertebrates, as a widespread trend during animal evolution. Among Hymenoptera, miniaturization has taken place in some parasitoid wasp lineages independently, and may have contributed to the diversity of species. However, the genomic basis of miniaturization is little understood. Diverged approximately 200 Ma, Telenomus wasps (Platygastroidea) and Trichogramma wasps (Chalcidoidea) have both evolved to a highly reduced body size independently, representing a paradigmatic example of convergent evolution. Here, we report a high-quality chromosomal genome of Telenomus remus, a promising candidate for controlling Spodoptera frugiperda, a notorious pest that has recently caused severe crop damage. The T. remus genome (129 Mb) is characterized by a low density of repetitive sequence and a reduction of intron length, resulting in the shrinkage of genome size. We show that hundreds of genes evolved faster in two miniaturized parasitoids Trichogramma pretiosum and T. remus. Among them, 38 genes exhibit extremely accelerated evolutionary rates in these miniaturized wasps, possessing diverse functions in eye and wing development as well as cell size control. These genes also highlight potential roles in body size regulation. In sum, our analyses uncover a set of genes with accelerated evolutionary rates in Tri. pretiosum and T. remus, which might be responsible for their convergent adaptations to miniaturization, and thus expand our understanding on the evolutionary basis of miniaturization. Additionally, the genome of T. remus represents the first genome resource of superfamily Platygastroidea, and will facilitate future studies of Hymenoptera evolution and pest control.

Toxicicity and Histological Changes Caused by Insecticides in Spodoptera frugiperda (Lepidoptera: Noctuidae) Eggs

Insecticides typically are used to control Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) larvae in corn crops; however, both eggs and larvae are affected by these applications. The purpose of this study was to evaluate the effects of 9 insecticides commonly used on corn crops in Brazil on ovicide and embryonic development of S. frugiperda. The insecticides were applied with an airbrush to the outer surface of eggs at 72, 96, 120, 144, and 168 h after oviposition. Larval emergence rates then were calculated. Eggs in the control and the alpha-cypermethrin and methomyl + novaluron treatment were evaluated by light microscopy to investigate possible histological changes in the embryos. The insecticides methomyl + novaluron, chlorantraniliprole + lambda-cyhalothrin, and deltamethrin reduced the emergence rate of S. frugiperda larvae. A mixture of alpha-cypermethrin and methomyl + novaluron did not affect the embryonic development of S. frugiperda; however, methomyl + novaluron-treated larvae did not emerge. Therefore, the insecticides methomyl + novaluron, chlorantraniliprole + lambda-cyhalothrin, and deltamethrin have an ovicidal effect and may be recommended for managing S. frugiperda.

Identification of yellow gene family and functional analysis of Spodoptera frugiperda yellow-y by CRISPR/Cas9

For a devastating agricultural pest, functional genomics promotes the finding of novel technology to control Spodoptera frugiperda, such as the genetics-based strategies. In the present study, 11 yellow genes were identified in Spodoptera frugiperda. The transcriptome analysis showed the tissue-specific expression of part yellow genes, which suggested the importance of yellow genes in some biological processes in S. frugiperda, such as pigmentation. Among these yellow genes, the expression profiles of yellow-y gene showed that it was expressed in all life stages. In order to realize the further study of yellow-y, we employed CRISPR/Cas9 system to knock out this gene. Following knock out, diverse phenotypes were observed, such as color changes in both larvae and adults. Different from the wild-type larvae and adults, G0 mutants were yellowed since hatching. However, no color difference was observed with the pupal cuticle between the wild-type and mutant pupae before the 8th day. On the basis of the single-pair strategy of G0 generation, the yellow-y gene was proved to be a recessive gene. The G1 yellowish larvae with biallelic mutations displayed a relatively longer development period than wild-type, and often generated abnormal pupae and moths. The deletion of yellow-y also resulted in a decline in the fecundity. The results revealed that yellow-y gene was important for S. frugiperda pigmentation, as well as in its development and reproduction. Besides, the present study set up a standard procedure to knock out genes in S. frugiperda, which could be helpful for our understanding some key molecular processes, such as functional roles of detoxification genes as insecticide resistance mechanisms or modes of action of insecticides to facilitate the management of this insect pest.

Assessing the Potential of Inoculative Field Releases of Telenomus remus to Control Spodoptera frugiperda in Ghana.

Simple SummaryThe fall armyworm (FAW) is a serious threat to maize production in Africa following its outbreak in 2016. Fortunately, some beneficial insects that could control FAW are already present in Africa, including Telenomus remus which parasitizes FAW eggs. Telenomus remus has been used in South America for biological control of FAW for several decades. Though T. remus is already present in Africa, little is known about its potential to be used for augmentative biological control of FAW under ecological conditions and agricultural systems in Africa. This study contributed to addressing this knowledge gap by conducting replicated field release trials of T. remus for FAW control in large maize plots in Ghana. In the major and minor rainy seasons, T. remus parasitized up to 33% and 100% of FAW egg masses, respectively, in the release plots. However, similar effectiveness of T. remus was recorded in non-treated control and farmers’ plots located at 150–400 m distance from release plots, indicating high dispersion of the parasitoid. A single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus, and could be considered in IPM strategies against FAW.In response to the threat caused by the fall armyworm to African maize farmers, we conducted a series of field release studies with the egg parasitoid Telenomus remus in Ghana. Three releases of ≈15,000 individuals each were conducted in maize plots of 0.5 ha each in the major and minor rainy seasons of 2020, and compared to no-release control plots as well as to farmer-managed plots with chemical pest control. No egg mass parasitism was observed directly before the first field release. Egg mass parasitism reached 33% in the T. remus release plot in the major rainy season, while 72–100% of egg masses were parasitized in the minor rainy season, during which pest densities were much lower. However, no significant difference in egg mass parasitism was found among the T. remus release plots, the no-release control plots and the farmer-managed plots. Similarly, no significant decrease in larval numbers or plant damage was found in the T. remus release fields compared to the no-release plots, while lower leaf and tassel damage was observed in farmer-managed plots. Larval parasitism due to other parasitoids reached 18–42% in the major rainy season but was significantly lower in the minor rainy season, with no significant differences among treatments. We did not observe significant differences in cob damage or yield among the three treatments. However, the lack of any significant differences between the release and no-release plots, which may be attributed to parasitoid dispersal during the five weeks of observation, would require further studies to confirm. Interestingly, a single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus and, thus, merits further investigation in the context of developing IPM strategies against FAW.

Preliminary study on the effect of using unmanned aerial vehicles (UAVs) to control Spodoptera frugiperda

AbstractSpraying insecticides by unmanned aerial vehicle (UAV) is an effective method to prevent and control Spodoptera frugiperda. This study investigated the influences of different UAV types, spray adjuvants, spray times, maize growth periods, and insecticides on S. frugiperda in three cities, Hainan Province, China. The results showed that at least two times are needed to spray insecticides using UAVs when controlling the S. frugiperda. Both UAVs had a substantially higher control effect and lower cost than artificial spray methods. Oil spray adjuvant Refei was more suitable for both UAVs than Tiancheng to control pests. Chlorantraniliprole had the best control effect of up to 90%. The control effects at the seedling stage and small bell stage of S. frugiperda were 94.3% and 91.3%, respectively. Spraying at 7:00 am and 7:00 pm by UAV of T20 had good control effect on S. frugiperda in three cities.

Bacillus thuringiensis Effect on the Vegetative Development of Cotton Plants and the Biocontrol of Spodoptera frugiperda

Bacillus thuringiensis (Bt) is used worldwide as a tool for controlling lepidopteran pests. Recent studies have demonstrated the possibility of its use as an endophytic organism, controlling insects and promoting plant growth. In this aspect, strains of Bt toxic to lepidopteran pests were inoculated both onto seeds and into cotton plants and were assessed for effectiveness in controlling Spodoptera frugiperda and its effect on promoting plant growth. It was observed that the results obtained from the interaction between the Bt strains (S1450 HD-1, S1905, S2122, S2124) and the cotton genotypes (BRS 8H, BRS Aroeira and BRS 286) showed different growth responses. The results also showed that all the strains may not be suitable to explore the biological control mechanism without undermining plant health. Therefore, the strain S2122, the BRS 8H genotype and seed inoculation were selected to continue the tests by using two concentrations of the bacterium. The results of Bt strain inoculation in seeds and into cotton plants showed that, although plant height, number of leaves, and development stage were influenced by Bt inoculation, overall, there was no significant improvement in the plant growth. The plants that were inoculated with Bt also interfered in the weight of Spodoptera frugiperda, however, did not cause the pest mortality. The collected results suggest that there is a close relationship between the Bt strain and the cotton crop and that colonizing mechanism of the bacterium can be useful in situations that there is an inefficiency of the control measures, since the endophytic Bt makes the pest more susceptible to be controlled by other practices, improving management effectiveness.

Synthesis, characterization of two matrine derivatives and their cytotoxic effect on Sf9 cell of Spodoptera frugiperda

The invasion of Spodoptera frugiperda has imposed a serious impact on global food security. Matrine is a botanical pesticide with a broad spectrum of insecticidal activity which was recommended for controlling Spodoptera frugiperda. In order to discover effective insecticide for Spodoptera frugiperda, two matrine derivatives modified with carbon disulfide and nitrogen-containing groups were systhesized. And their inhibition activities on Sf9 cell were evaluated. The structural configuration of compounds were characterized by IR, HPLC, MS, NMR and XRD, with yields of 52% and 65%, respectively. The IC50 of the two newly synthesized compounds on Sf9 cell reduced to 0.648 mmol/L and 1.13 mmol/L, respectively, compared with that of matrine (5.330 mmol/L). In addition, microscopic observation of Sf9 cell treated with the compounds showed that the number of adherent cells decreased, the cells shrunk, vacuolated and apoptotic bodies appeared. The two newly synthesized compounds exhibited better inhibitory effect on Sf9 cell than that of the parent matrine, suggesting that the positive effect of the introduction of 1-pyrrolidinecarbodithioate and diethylcarbamodithioate groups to matrine. The morphological observation of Sf9 cell induced by derivatives indicated that apoptosis induction may be a mechanism that inhibits insect cell proliferation and exerts insecticidal effect.

Release density, dispersal capacity, and optimal rearing conditions for Telenomus remus, an egg parasitoid of Spodoptera frugiperda, in maize

ABSTRACT We determined the release density, dispersal capacity, and optimal storage conditions for the parasitoid Telenomus remus Nixon to control Spodoptera frugiperda (J.E. Smith). Each of eighty plants within an 829-m2 plot were artificially infested with one S. frugiperda egg mass in a maize field. These plants were distributed evenly along four concentric squares which allowed for 14 different distances from a central release point (range 3.6–20.3 m). Egg parasitoids were released at four densities (0; 100,000; 150,000; and 200,000 adults/ha) in two vegetative maize growth stages (V4-5 and V8-9). After a 48-h exposure, egg masses were retrieved to evaluate parasitism rates. Spodoptera frugiperda egg parasitism by T. remus did not differ among the three parasitoid release densities. Egg parasitism decreased linearly with increasing distance from the release point, but this was influenced by the crop’s phenological stage. Egg parasitism was 28% higher at the older than younger growth stages, and dispersal distance and area of dispersal were 35% and 16% lower, respectively, at the older stage. In the laboratory, we evaluated the effects of six storage periods (0, 3, 6, 9, 12, and 15 days) of S. frugiperda eggs at four temperatures (5, 10, 15, and 20°C) on T. remus adult emergence. Our results showed the highest emergence when eggs were stored at 15°C for ≤9 days. Altogether, we identified important mass release and rearing parameters for augmentative biocontrol of T. remus on S. frugiperda eggs that may help reduce production and marketing costs.

Plant Selection for the Establishment of Push-Pull Strategies for Zea mays-Spodoptera frugiperda Pathosystem in Morelos, Mexico.

Regulations imposed on the use of chemical insecticides call for the development of environmental-friendly pest management strategies. One of the most effective strategies is the push–pull system, which takes advantage of the behavioral response of the insect to the integration of repellent stimuli; it expels the pest out of the main crop (push), while attracting stimuli (attractants) pull the pest to an alternative crop or trap (pull). The objective of this study was to design a push–pull system to control Spodoptera frugiperda in maize crops (Zea mays) in Morelos, Mexico. Data on reproductive potential, larvae development, food consumption and olfactometry were used to obtain a Trap Plant Selection Index (TRAPS) based on Principal Component Analysis. This TRAPS was used to select the most suitable plants. The degree of repellency of potential plants to be used as the trap crop was studied with four-way olfactometers. S. frugiperda females oviposited more eggs on Brachiaria hybrid cv. Mulato II, Panicum maximum cv. Mombasa and Panicum maximum cv. Tanzania than on Z. mays, regardless of the fact that these plants delayed the development of their offspring. Dysphania ambrosioides, Tagetes erecta and Crotalaria juncea were less attractive to S. frugiperda females. Therefore, the former plants could be used as crop traps, and the latter as intercropped repellent plants in a push–pull system.

Microsclerotia production of Metarhizium spp. for dual role as plant biostimulant and control of Spodoptera frugiperda through corn seed coating

The fungal genus Metarhizium comprises entomopathogenic species capable of producing overwintering structures known as microsclerotia. These structures offer many advantages in pest control due to the formation of infective conidia in situ and their persistence in the environment under adverse conditions. In addition, the in vitro production of Metarhizium microsclerotia under controlled liquid fermentation is faster and with greater process control than the production of aerial conidia. However, the potential of Metarhizium microsclerotia to control pests from the orders Lepidoptera and Hemiptera is unexplored. In this study, we examined the ability of Metarhizium spp. microsclerotia to promote corn growth and to provide plant protection against Spodoptera frugiperda (Lepidoptera: Noctuidae) and Dalbulus maidis (Hemiptera: Cicadellidae), through seed coating using microsclerotial granules. A screening to find higher microsclerotia producers was conducted by culturing 48 native Brazilian isolates of Metarhizium spp. (Metarhizium anisopliae, Metarhizium robertsii, Metarhizium humberi and Metarhizium sp. indeterminate). The best microsclerotia producers, M. anisopliae ESALQ1814, M. robertsii ESALQ2450 and M. humberi ESALQ1638 improved the leaf area, plant height, root length, and dry weight of plants compared to un-inoculated plants. Significant reduction in S. frugiperda survival (mortality > 55% after 7 days) was observed when larvae were fed on corn plants treated with any of the three Metarhizium species. Conversely, survival of D. maidis adults were unaffected by feeding on fungus-inoculated plants. Our results suggest that microsclerotia of Metarhizium spp. may act as biostimulants and to provide protection against S. frugiperda in corn through seed coating, thus adding an innovative strategy into the integrated management of this major worldwide pest.