Control Of Insect Pests Research Articles

Isolation and identification of bacteria from the invasive pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) and evaluation of their biocontrol potential.

As an alternative to chemical insecticides, gut bacteria of insects could be used to control insect pests. In this study, bacteria associated with Tuta absoluta, an invasive species that has developed resistance to chemical insecticides, were isolated, and their potential for pest control was investigated. We isolated 13 bacteria from larvae of the pest and identified the isolates on the basis of their morphological, physiological, biochemical, and molecular characteristics as Bacillus thuringiensis (Ta1-8), Staphylococcus petrasii (Ta9), Citrobacter freundii (Ta10), Chishuiella changwenlii (Ta11), Enterococcus casseliflavus (Ta12), and Pseudomonas tremae (Ta13). A laboratory screening test at 109 cfu/ml showed that B. thuringiensis (Bt) isolates caused more than 90% mortality after 3 days. Among the isolates, Bt-Ta1 showed the highest mortality in a short time. The LC50 and LC90 values for Bt-Ta1 were estimated to be 1.2 × 106 and 2 × 109 cfu/ml, respectively. Detailed characterization of Bt-Ta1 revealed that it is one of the serotypes effective on lepidopterans and contains the genes cry1Aa, cry2Aa, and vip3Aa, which encode lepidopteran toxic proteins. Bt-Ta1 isolate has been shown to have the potential to be used in the integrated management of Tuta absoluta.

Stored product pest Nemapogon variatella (Clemens): Identification of sex pheromone, putative antagonist and mitotype characterization

AbstractNemapogon variatella (Clemens) (Lepidoptera: Tineidae) is a worldwide widespread stored product pest that damages grain, dried fruits and mushrooms. The most powerful and environmentally friendly tool for insect pest monitoring and control is pheromone application. In our study, we revealed for the first time that the females of N. variatella release (3Z,13Z)‐octadecadien‐1‐ol – a single compound that activates olfactory receptors in the antenna of conspecific males. These data allow to assign this compound, which has been known as an attractant for males only, to the category of sex pheromones of N. variatella moths. Males' olfactory system is sensitive not only to the sex pheromone compound but also to (3E,13Z)‐octadecadien‐1‐ol as well. (3E,13Z)‐octadecadien‐1‐ol is attributed to putative pheromone antagonists. During the analysis of genetic diversity, six mitotypes of N. variatella CO1‐5′ were detected and preliminary named Mit1–Mit6. The obtained high haplotype diversity (Hd = 0.796) and low nucleotide diversity (Pi = 0.007) suggest that this species may have undergone a recent population expansion.

Endophytic establishment of native Bacillus thuringiensis strain in maize plants and its efficacy against Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

BackgroundBacillus thuringiensis (Bt) is known as the most successful microbial insecticide worldwide used against lepidopteran insect pests in agriculture. Native Bacillus isolate VKK5 showing insecticidal activity against Spodoptera frugiperda (FAW) (J.E. Smith) (Lepidoptera: Noctuidae) was characterized as B. thuringiensis (BtVKK5) on a morphological and molecular basis. Recent research has shown that Bt can be established as an endophytic organism for controlling insect pests. The present work aimed at assessing the colonization of BtVKK5 as an endophyte in five maize cultivars by seed treatment (ST), soil drenching (SD), foliar application (FA) and combination of all methods (ST + SD + FA) and its bioefficacy against neonates of FAW.ResultsEstablishment of inoculated BtVKK5 as endophytes in five maize cultivars, viz. Pusa HQPM7 Improved, Pusa Jawahar Hybrid Maize 1, Pusa Vivek Hybrid 27 Improved (PVH27I), Pusa HQPM5 Improved and DMRH 1301, was confirmed by re-isolating from the leaves of the plant on ampicillin-selected agar plates. Estimation of colony-forming units per gram of leaf showed that there was a significant difference in colonization of the Bt strain among maize cultivars by different inoculation methods. The colonies were further substantiated by the amplification of cry1A and cry1E genes. Bioefficacy studies showed the highest mortality (50%) in the ST + FA + SD inoculation method, followed by ST (40%) in PVH27I. Moreover, growth inhibition was observed in survived larvae on inoculated plants vis-a-vis control.ConclusionEstablishment of Bt strain as an endophyte in maize plants, complemented with insecticidal activity, could possibly lead to an innovative approach to the management of S. frugiperda and other borers.

Isolation, morphological characterization, and screening virulence of Beauveria bassiana and Metarhizium robertsii fungal isolates on Galleria mellonella.

Entomopathogenic fungi exists naturally in plants as an asymptote and have the potential to reduce the population of insect pests through indirect interactions. This study was conducted to detect and characterize the endophytic fungi Beauveria bassiana and Metarhizium robertsii from the rhizosphere soil of tomato plants and their virulence effect on Galleria melonella. From the rhizosphere soil of 40 tomato fields, three Beauveria bassiana and seven Metarhizium robertsii isolates were isolated using the galleria bait method. All fungi isolate were morphologically characterized by their colony color, shape, and surface texture. Isolates with the highest percentages of germination, conidial yield, and radial growth were selected, and their virulence was evaluated on second instar larvae of Galleria melonella under laboratory conditions. In this study, Beauveria bassiana showed white colony color and aseptate hyphae, whereas Metarhizium robertsii showed dark green to light green colony color and septate hyphal structures. Maximum spore production and conidial length were obtained by Beauveria bassiana isolate APPRC-27 with 2.67x10 7 spores ml -1 and 3.24 µm, respectively. Colony radial growth rates ranged from 1.73 to 3.24 mm day -1. The results revealed that the highest mortality rate of Galleria melonella (100%) was obtained by Metarhizium robertsii isolates K-61 and K-102 at a concentration of 1x10 8 conidial ml -1 at 7 days post-inoculation. The lowest mortality rate was registered by Metarhizium robertsii isolate RST-11. In the present study, isolates that produced the most spores and had the highest germination rates were the most virulent to Galleria mellonella second instar larvae. Therefore, virulent entomopathogenic fungi, Beauveria bassiana and Metarhizium robertsii, are promising bioagents for the control of insect pests.

Chitinase of Trichoderma longibrachiatum for control of Aphis gossypii in cotton plants

Chitinase-producing fungi have now engrossed attention as one of the potential agents for the control of insect pests. Entomopathogenic fungi are used in different regions of the world to control economically important insects. However, the role of fungal chitinases are not well studied in their infection mechanism to insects. In this study, Chitinase of entomopathogenic fungi Trichoderma longibrachiatum was evaluated to control Aphis gossypii. For this purpose, fungal chitinase (Chit1) gene from the genomic DNA of T. longibrachiatum were isolated, amplified and characterised. Genomic analysis of the amplified Chit1 showed that this gene has homology to family 18 of glycosyl hydrolyses. Further, Chit1 was expressed in the cotton plant for transient expression through the Geminivirus-mediated gene silencing vector derived from Cotton Leaf Crumple Virus (CLCrV). Transformed cotton plants showed greater chitinase activity than control, and they were resistant against nymphs and adults of A. gossypii. About 38.75% and 21.67% mortality of both nymphs and adults, respectively, were observed by using Chit1 of T. longibrachiatum. It is concluded that T. longibrachiatum showed promising results in controlling aphids by producing fungal chitinase in cotton plants and could be used as an effective method in the future.

Characterization of a new isolate of Beauveria bassiana in Algeria and evaluation of its pathogenicity against the cowpea aphid (Aphis craccivora Koch)

BackgroundThe cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphidiidae) is a polyphagous aphid species that causes various damage on different crops. The conventional method of controlling this pest is the use synthetic insecticides that threaten both the environmental safety and human health. Moreover, it contributes to the emergence of insecticide-resistant generations. Hence, relying on Entomopathogenic fungi (EPF) remains one of the most safe and effective alternative solutions to control insect pests. For the mentioned reasons, the EPF, Beauveria bassiana was isolated and characterized; besides, its efficiency against adults’ A. craccivora was evaluated both in the laboratory and in the greenhouse.ResultsA new isolate of B. bassiana was isolated from collected cadavers’ insects associated with the population of A. craccivora in a rural area in the Northwest of Algeria. This isolate was identified on the basis of its morphological and molecular characteristics and was referred to as B. bassiana BBAA. The enzymatic activities of this isolate revealed a high production of chitinase, protease and lipase, without any production of amylase. The use of different concentrations of B. bassiana BBAA conidia against A. craccivora led to a high mortality rate, ranging from 64 to 74% mortality on the seventh day post-treatment in vitro and 58 to 70% in greenhouse.ConclusionVirulence and enzymatic activities produced by B. bassiana BBAA demonstrated the necessity to exploit entomopathogenic fungi (EPFs) in pest control.

Investigating the role of the ROS/CncC signaling pathway in the response to xenobiotics in Spodoptera frugiperda using Sf9 cells

Spodoptera frugiperda (fall armyworm, FAW) is an invasive polyphagous lepidopteran pest that has developed sophisticated resistance mechanisms involving detoxification enzymes to eliminate toxic compounds it encounters in its diet including insecticides. Although its inventory of detoxification enzymes is known, the mechanisms that enable an adapted response depending on the toxic compound remain largely unexplored. Sf9 cells were used to investigate the role of the transcription factors, Cap n′ collar isoform C (CncC) and musculoaponeurotic fibrosarcoma (Maf) in the regulation of the detoxification response. We overexpressed CncC, Maf or both genes, and knocked out (KO) CncC or its repressor Kelch-like ECH associated protein 1 (Keap1). Joint overexpression of CncC and Maf is required to confer increased tolerance to indole 3-carbinol (I3C), a plant secondary metabolite, and to methoprene, an insecticide. Both molecules induce reactive oxygen species (ROS) pulses in the different cell lines. The use of an antioxidant reversed ROS pulses and restored the tolerance to I3C and methoprene. The activity of detoxification enzymes varied according to the cell line. Suppression of Keap1 significantly increased the activity of cytochrome P450s, carboxylesterases and glutathione S-transferases. RNAseq experiments showed that CncC mainly regulates the expression of detoxification genes but is also at the crossroads of several signaling pathways (reproduction and immunity) maintaining homeostasis. We present new data in Sf9 cell lines suggesting that the CncC:Maf pathway plays a central role in FAW response to natural and synthetic xenobiotics. This knowledge helps to better understand detoxification gene expression and may help to design next-generation pest insect control measures.

Diversity and Abundance of Entomopathogenic Fungi and Their Hosts in Rice Fields of Kembang Mertha Village-Bolaang Mongondow

The diversity of entomopathogenic fungi in an area can provide information about the potential for controlling insect pests. This is important to do to find suitable biological control agents to reduce the impact of using synthetic pesticides. This research was conducted to look at the diversity and abundance of entomopathogenic fungi and their host insects, so that potential entomopathogenic fungal and pest species were identified in the rice fields of Kembang Mertha Village. The results obtained were four species of host insects, namely Leptocoarisa oratorius, Schotinopara coarctata, Ricelia dorsalis and Nilaparvata lugens, and three species of entomopathogenic fungi, namely Beauveria bassiana, Metarhizium sp. and Hirsutella sp.. The host insect diversity indices in the medium category were S. coarctata (1.10) and N. lugens (1.04) and for entomopathogenic fungi, the three fungal species found were in the medium category respectively B. bassiana (1.31), Metarhizium sp. (1.07) and Hirsutella sp. (1.05). The highest abundance index values ​​for host insects were S. coarctata (84.62%) and N. lugens (50%), while for pathogenic fungi were Hirsutella sp. (43.73%).

Fabrication of Carum copticum essential oil-loaded chitosan nanoparticles and evaluation its insecticidal activity for controlling Rhyzopertha dominica and Tribolium confusum.

Plant essential oils (EOs) can be used as a feasible tool for insect pest control. Nanoparticle formulations of plant EOs can improve the efficiency and stability of EOs, as well as insecticidal potential. In this study, Carum copticum L. essential oil-loaded nanoparticles (OLNs) were prepared via an oil-in-water emulsion, followed by droplet solidiffication via ionic gelation using a cross-linker, sodium tripolyphosphate (TPP). The nanoparticles were characterized by ultraviolet and visible (UV-Vis) spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), laser light scattering (LS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Moreover, the insecticidal activity of C. copticum EO and OLNs was evaluated against Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Tribolium confusum Jacquelin du Val. (Coleoptera: Tenebrionidae). In addition, their effectiveness was assessed on the progeny production of tested insect species. The loading efficiency ranged from 34.33 to 84.16% when the chitosan to EO weight ratio was 1:1.25 and 1:0.5, respectively. The loading efficiency decreased with increasing EO content in the nanoparticles. The OLN particles exhibited spherical shape. The particle size was in the range 120-223.6 nm and increased with the increase of EO to chitosan ratio. So that the largest mean particle size (223.6 nm) was reported in the 1:1.25 weight ratio of chitosan to the EO. The mortality percentage of R. dominica and T. confusum adults were 74 and 57% when exposed for 7 days to 2000 mg/kg of OLNs at the 1:1.25 weight ratio, while EO caused 62 and 44% mortality on both insect species, respectively. Therefore, OLNs can potentially improve the insecticidal activity of C. copticum EO and could be applied to facilitate control of stored-product insect pests.

Biocontrol effect of entomopathogenic fungi Metarhizium anisopliae ethyl acetate-derived chemical molecules: An eco-friendly anti-malarial drug and insecticide.

Insect pests represent a major threat to human health and agricultural production. With a current over-dependence on chemical insecticides in the control of insect pests, leading to increased chemical resistance in target organisms, as well as side effects on nontarget organisms, the wider environment, and human health, finding alternative solutions is paramount. The employment of entomopathogenic fungi is one such potential avenue in the pursuit of greener, more target-specific methods of insect pest control. To this end, the present study tested the chemical constituents of Metarhizium anisopliae fungi against the unicellular protozoan malaria parasite Plasmodium falciparum, the insect pests Anopheles stephensi Listen, Spodoptera litura Fabricius, and Tenebrio molitor Linnaeus, as well as the nontarget bioindicator species, Eudrilus eugeniae Kinberg. Fungal crude chemical molecules caused a noticeable anti-plasmodial effect against P. falciparum, with IC50 and IC90 values of 11.53 and 7.65 µg/mL, respectively. The crude chemical molecules caused significant larvicidal activity against insect pests, with LC50 and LC90 values of 49.228-71.846 µg/mL in A. stephensi, 32.542-76.510 µg/mL in S. litura, and 38.503-88.826 µg/mL in T. molitor at 24 h posttreatment. Based on the results of the nontarget bioassay, it was revealed that the fungal-derived crude extract exhibited no histopathological sublethal effects on the earthworm E. eugeniae. LC-MS analysis of M. anisopliae-derived crude metabolites revealed the presence of 10 chemical constituents. Of these chemicals, three major chemical constituents, namely, camphor (15.91%), caprolactam (13.27%), and monobutyl phthalate (19.65%), were highlighted for potential insecticidal and anti-malarial activity. The entomopathogenic fungal-derived crude extracts thus represent promising tools in the control of insect pests and malarial parasites.

A Systematic Review of the Bioactivity of Jatropha curcas L. (Euphorbiaceae) Extracts in the Control of Insect Pests

The use of botanical extracts of the plant Jatropha curcas (Euphorbiaceae) represents a valuable alternative to control insect pests and avoid the detrimental effects on the environment and health that arise due to synthetic chemical insecticides. Thus, we conducted a systematic review to summarize the published evidence on the bioactivity of J. curcas against insect pests. Electronic databases were searched to identify studies that assessed J. curcas extracts against insect pests in various types of crops. We included 39 articles that reported the insecticidal and insectistatic activity of several botanical extracts from J. curcas against insects of eight different taxonomic orders. The evidence demonstrates that aqueous and methanolic extracts from seeds and leaves, seed oil, and petroleum ether seed extracts were effective against insect pests of stored grains, aphids of cabbage and sorghum, fruit flies, and desert locusts. The extracts caused high mortality, controlled the populations, reduced oviposition, diminished hatchability, and increased the antifeedant effect. However, the type of solvent used to obtain the botanical extract and the method of application (contact or food) are fundamental to increase its bioactivity. Therefore, botanical extracts from seeds and leaves of J. curcas should be considered as an alternative against insect pests and may be incorporated into integrative and sustainable management for insect control.

Transcriptome-Wide Identification of Cytochrome P450s and GSTs from Spodoptera exigua Reveals Candidate Genes Involved in Camptothecin Detoxification

The application of camptothecin (CPT) and its derivatives to control insect pests has generated significant interest. This study investigated the enzymatic response of cytochrome P450 monooxygenase (CYP) and glutathione S-transferase (GST) genes in the fat body cells of Spodoptera exigua after 10 μM CPT treatment. Additionally, we examined the effects of CPT on the growth and development of S. exigua larvae and detected the relative expression levels of selected CYP and GST genes during the CPT treatment period. Twenty-one CYP and 17 GST genes were identified from the fat body cells of S. exigua by comparative transcriptomic analyses. The relative expression of ten CYP and seven GST genes changed significantly, which suggested that these CPYs and GSTs may be involved in CPT metabolism. During exposure to CPT for 10 days, the development of S. exigua larvae was delayed and was characterized by weight inhibition and a prolonged period of development. The relative expression levels of the selected four CYP genes, CYP9A27, CYP9A186, CYP337B5, CYP321A8, and one GST gene, GSTe7, were significantly changed by CPT treatment compared to the control group. These generated data provide a basis for identifying the CPT metabolism/detoxification genes of S. exigua at the molecular level.

Semiochemicals for controlling insect pests

Semiochemicals for controlling insect pests

Host stage affects oviposition-related behaviours, development progression and reproductive output in a native hyperparasitoid of the solenopsis mealybug invading Asian regions

ABSTRACT Native hyperparasitoids may readily expand their host range by including non-native parasitoids that are introduced in classical biological control of pest insects. Here we report our observation on biology of Cheiloneurus nankingensis (Hymenoptera: Encyrtidae), an obligate hyperparasitoid attacking non-native parasitoid Aenasius arizonensis residing in Phenacoccus solenopsis mealybugs that have invaded into Asian regions. We measured durations of antennae-tapping, ovipositor-drilling and ovipositor-probing/ovipositing behaviours by C. nankingensis wasps on parasitised mealybugs with the host at either larval or pupal stage and on the unparasitised mealybug as the control. The ovipositor-probing/ovipositing duration was much longer on a pupal host than on the larval while shortest on the control. We then observed offspring development progression of C. nankingensis at attacking either egg, larva or pupa of its host by daily dissecting hyperparasitised mealybugs. The development was faster in a larval or pupal host than in the egg. Finally, our measurements of the reproductive output showed that C. nankingensis wasps during 14 days after the emergence attacked more parasitised mealybugs and produced more offspring reaching adulthood when ovipositing in the mealybug with a host larva than with a pupa. Our results from this study suggest that C. nankingensis may employ the ovipositor to probe for the host within a mealybug and the host at the larval stage is of high quality for the reproduction.

Insect-trapping glues made of natural rubber: Effects of nonrubber components and rubber molar mass on performance

An easy-to-prepare glue was produced from natural rubber (NR) latex and environmentally benign chemicals for use in control of insect pests in greenhouses. The effects of non-rubber components and the molar mass (MM) of NR in the latex and the glue on adhesion performance of the glues are reported. Glues were produced using five latex types: commercial high-ammonia concentrated latex (HA), fresh latex (FL), skim latex (SK), urea deproteinized latex (UD), and saponified latex (SP). The latexes’ characteristics (e.g., protein content, phospholipid content, gel content, and molar mass of NR chains) and the characteristics of the resulting glues (i.e., drying time, molar mass of NR chains, and adhesion performance) were evaluated by principal component analysis (PCA). The NR glues made of HA and SP latex types were found to have an adhesion performance comparable to commercial insect trapping glues. The HA latex was natural, more economical, and required less processing than the SP latex. PCA demonstrated that the adhesion performance of the glues correlated strongly to the gel content and the molar mass of the NR chains in the glue and the latex. Increased values of all these variables improved the cohesive strength of the glue. The HA glue was tested in a greenhouse to confirm its effectiveness: it showed an insect capturing efficacy of ∼68% of a commercial glue. The lower performance was caused by an absence of vulcanization, leading to creep behavior and degradation of the rubber chains in the hot environment of the greenhouse.

Companion plants and straw mulch reduce cabbage stem flea beetle (Psylliodes chrysocephala) damage on oilseed rape.

Plant diversification, especially sowing crops with the addition of companion plants has been demonstrated as a suitable practice to increase insect pest control in multiple cropping systems. Since the ban on use of neonicotinoid seed treatments in oilseed rape (OSR), the harvested area has reduced significantly in Europe, mainly because of the damage caused by cabbage stem flea beetle (Psylliodes chrysocephala). Several companion plants such as legumes and other species of Brassicaceae have been reported as potential companions for OSR but robust evaluation of their efficiency to reduce cabbage stem flea beetle damage in replicated trials is lacking. Four field trials were conducted in the UK and Germany to test the effect of different companion plants, or the addition of straw mulch, on cabbage stem flea beetle adult feeding and larval infestation in OSR. We found significant differences in the level of feeding damage between treatments in all experiments. Combinations of OSR with cereal companion plants or with straw mulch showed the strongest reduction in adult feeding damage. A protective effect of legumes was also observed in one trial. Differences in larval infestation were also observed between treatments but were not consistent and might be more related to the OSR plant biomass than to treatments. This study shows that companion planting can protect OSR crops from cabbage stem flea beetle adult feeding damage. We show for the first time that not only legumes, but also cereals and the application of straw mulch can have a strong protective effect on the crop. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ways for the Prosperity of Farmers in Western Hills and Terai, Nepal

The Institute of Agriculture and Animal Science (IAAS) under Tribhuvan University (TU) has launched the internship programme me for their final semester students studying under-graduate level since 2014/15 in its all constituent and affiliated campuses. About 106 UPA mini-theses accomplished by 221 B.Sc. Ag. graduates from the Prithu Technical College (PTC) libraries were systematically arranged and categorized in chronological order based on the disciplinary subjects and thematic areas, and the technologies have been recommended to scale-out for the prosperity of the farmers in the western Tertian mid-hill agro-ecology of Lumbini and adjoining provinces in Nepal. The review revealed that the researches at PTC were concentrated majorly on major food grain crops with five major themes viz. varietal evaluation, crop management, soil nutrient, weed and insect pest management. The review further revealed that the adequate number of researches were in the vegetable crops specially in production packages and value-chain analysis followed by the control of insect pests and diseases both in on-farm and storage structures, suggesting to follow the integrated pest management (IPM) approach. Varietal testing in major field and vegetable crops, and economic survey of chamomile, marigold, honeybees, broiler chicken, cardamom and ginger and oyster mushroom cultivation practices are the newly defined arena to be adopted for harnessing the prosperity of the farmers of the western hills and Terai region in Nepal and its adjoining congenial agro-climatic environment. Future collaboration with the various agriculture related national and international organizations as adopted by PTC on these recent years has to be continued and strengthened further to extrapolate the UPA research innovations obtained from the graduate student’s mini-thesis works.

Screening of Toxic Effects of Neonicotinoid Insecticides with a Focus on Acetamiprid: A Review.

Recently, neonicotinoids have become the fastest-growing class of insecticides in conventional crop protection, with extensive usage against a wide range of sucking and chewing pests. Neonicotinoids are widely used due to their high toxicity to invertebrates, simplicity, flexibility with which they may be applied, and lengthy persistence, and their systemic nature ensures that they spread to all sections of the target crop. However, these properties raise the risk of environmental contaminations and potential toxicity to non-target organisms. Acetamiprid is a new generation insecticide, which is a safer alternative for controlling insect pests because of its low toxicity to honeybees. Acetamiprid is intended to target nicotinic acetylcholine receptors in insects, but its widespread usage has resulted in negative impacts on non-target animals such as mammals. This review summarizes in vivo and in vitro animal studies that investigated the toxicity of specific neonicotinoids. With summarized data, it can be presumed that certain concentrations of neonicotinoids in the reproductive system cause oxidative stress in the testis; spermatogenesis disruption; spermatozoa degradation; interruptions to endocrine function and Sertoli and Leydig cell function. In the female reproductive system, acetamiprid evokes pathomorphological alterations in follicles, along with metabolic changes in the ovaries.

Bird taxonomic and functional diversity, group- and species-level effects on a gradient of weevil-caused damage in eucalypt plantations

The relative contribution of bird communities to insect pest control has been seldom estimated using trait-based functional diversity indices, in opposition to the general usage of taxonomic indices simply based on the presence and abundance of species. Moreover, few studies attempted to quantify the explicit contribution of functional groups or species of birds to the control of insect pests. We investigated eucalypt plantations under a gradient of defoliation caused by the eucalyptus weevil Gonipterus platensis to assess how avian insectivory links with (1) taxonomic and (2) functional diversity indices, and with (3) groups and (4) species of functional insectivores. In agreement with our hypothesis, weevil-caused damage was negatively correlated to avian insectivory in the four studied approaches. Taxonomic diversity indices consistently presented a negative correlation with weevil-caused damage, but, contrary to our expectation, functional diversity indices were defective predictors of weevil-caused damage in eucalypt stands. Results were further explicit in the analyses conducted with groups and species of functional insectivores, wherein significant lower levels of weevil-caused damage in eucalypt stands were mainly associated with the higher abundance of canopy foragers, even though ground- and understory-gleaning species also provided competitive models at the species-level. This study establishes the importance of using multivariate trait-based approaches to understand how functional diversity drives ecosystem services, as it is here demonstrated for avian insectivory in eucalypt plantations. Top-down trophic control of the eucalyptus weevil by birds can reduce damage in areas where functional insectivorous birds aggregate.

The Study of Cell-Penetrating Peptides to Deliver dsRNA and siRNA by Feeding in the Desert Locust, Schistocerca gregaria.

RNA(i) interference is a gene silencing mechanism triggered by double-stranded (ds)RNA, which promises to contribute to species-specific insect pest control strategies. The first step toward the application of RNAi as an insecticide is to enable efficient gene silencing upon dsRNA oral delivery. The desert locust, Schistocerca gregaria is a devastating agricultural pest. While this species is responsive to dsRNA delivered by intra-hemocoelic injection, it is refractory to orally delivered dsRNA. In this study, we evaluated the capacity of five cell-penetrating peptides (CPPs) to bind long dsRNA and protect it from the locust midgut environment. We then selected the CPP EB1 for further in vivo studies. EB1:dsRNA complexes failed to induce RNAi by feeding. Interestingly, we observed that intra-hemocoelic injection of small-interfering (si)RNAs does not result in a silencing response, but that this response can be obtained by injecting EB1:siRNA complexes. EB1 also protected siRNAs from midgut degradation activity. However, EB1:siRNA complexes failed as well in triggering RNAi when fed. Our findings highlight the complexity of the dsRNA/siRNA-triggered RNAi in this species and emphasize the multifactorial nature of the RNAi response in insects. Our study also stresses the importance of in vivo studies when it comes to dsRNA/siRNA delivery systems.