Biological Control Of Insect Pests Research Articles

Genomic analyses of Biston suppressaria nucleopolyhedrovirus: a viral isolate obtained from the tea looper caterpillar, Biston suppressaria (Guenée, 1857).

We described the complete genome sequence of a novel baculovirus isolate of species Buzura suppressaria nucleopolyhedrovirus, called by isolate CNPSo-25. The occlusion bodies were found to be polyhedral in shape and to contain virions with singly embedded nucleocapsids. The size of the genome is 121,377bp with a G+C content of 36.7%. We annotated 131 ORFs that cover 90.42% of the genome. Moreover, phylogenetic inference indicated that CNPSo-25 is a member ofgenus Alphabaculovirus that clustered together with two other Chinese isolates of the same species. We called the virus by Biston suppressaria nucleopolyhedrovirus isolate CNPSo-25 (BisuNPV-CNPSo-25), as Buzura was placed inside the lepidopteran genus Biston. As expected, we detected intra-population variability in the virus sample when the novel isolate was compared to the Chinese isolates: 292 single nucleotide variants were found in the genome, with 181 affecting the protein product. The closest representatives of other species to BisuNPV-CNPSo-25 was found to be Sucra jujuba nucleopolyhedrovirus and Hyposidra talaca nucleopolyhedrovirus, two other virus isolates of geometrid caterpillars. The study of baculovirus genomes is of importance for the development of tools for insect pest biological control and biotechnology.

Ecological Characterisation of Native Isolates of Heterorhabditis indica from Viti Levu, Fiji Islands.

Entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are obligate parasites of soil inhibiting insects. EPNs are being widely researched as promising biocontrol agents for a wide range of agricultural pests. It is known that strains of EPNs isolated from different geographical regions differ in their attributes, such as host-finding ability, host range, infectivity, reproduction, and environmental stress tolerance. A precise knowledge of these factors is therefore an essential pre-requisite for devising successful strategies to use these nematodes in biological control programmes. Thus, ecological characterisation of the EPN Heterorhabditis indica (Rhabditida: Heterorhabditidae) newly isolated and representing the only species of EPN reported from the island of Viti Levu, Fiji was carried out using Galleria mellonella larvae (L) (Pyralidae: Galleriinae) as hosts to allow comparisons between bioassays conducted in different laboratories around the world. Temperature data showed that native isolates of H. indica are warm-adapted nematodes with thermal range for infectivity between 15˚C and 35˚C and can reproduce between 20˚C and 30˚C. They are highly virulent with LC50 values against G. mellonella ranging from 2.8 IJ to 3.8 IJ/larva. However, they showed poor desiccation tolerance and fail to infect hosts in soil with moisture levels below 8%. They showed a moderate level of hypoxic tolerance and can be stored at 15˚C for 4 months. Results also showed great variability within the selected native isolates of H. indica. Beneficial traits for selected isolates were added up to identify a superior candidate. The current study also suggested that the thermal niche breadth for infection can differ among conspecific strains of an EPN species. The results of this experimental study on ecological aspects of these native isolates of H. indica should form a basis for their potential use in biological control of insect pests in Fiji.

Endophytic Microorganisms Associated with the Biological Control of Insect Pests in Agriculture

Endophytic Microorganisms Associated with the Biological Control of Insect Pests in Agriculture

Bracon wasps for ecological pest control-a laboratory experiment.

Biological control of pest insects by natural enemies may be an effective, cheap and environmentally friendly alternative to synthetic pesticides. The cosmopolitan parasitoid wasp species Bracon brevicornis Wesmael and B. hebetor Say (Hymenoptera: Braconidae) use lepidopteran species as hosts, including insect pests like Ephestia kuehniella or Ostrinia nubilalis. Here, we compare the reproductive success of both Bracon species on E. kuehniella in a laboratory experiment. We asked (1) how the reproductive success on a single host larva changes with temperature, (2) how it changes with temperature when more host larvae are present and (3) how temperature and availability of host larvae influence the efficacy of Bracon species as biological control agents. In general, differences between B. brevicornis and B. hebetor have been small. For rearing both Bracon species in the laboratory on one host larva, a temperature between 20–27 °C seems appropriate to obtain the highest number of offspring with a female-biased sex ratio. Rearing the braconid wasps on more than one host larva revealed a higher number of total offspring but less offspring per host larva on average. Again, highest numbers of offspring hatched at 27 °C and the sex ratio was independent from temperature. Although no parasitoids hatched at 12 °C and only few at 36 °C, host larvae were still paralyzed. The efficacy of B. brevicornis was higher than 80% at all numbers of host larvae presented at all temperatures while the efficacy of B. hebetor was less than 80% at 12 °C and 27 °C at low numbers of host larvae presented. In conclusion, practitioners can use either B. brevicornis or B. hebetor at low and high temperatures and at varying host densities to achieve high pest control efficacy.

Gut microbiota mediate Plutella xylostella susceptibility to Bt Cry1Ac protoxin is associated with host immune response

Insect gut microbiotas have a variety of physiological functions for host growth, development, and immunity. Bacillus thuringiensis (Bt) is known to kill insect pests by releasing insecticidal protoxins, which are activated in the insect midgut. However, the interplay among Bt infection, host immunity, and gut microbiota are still unclear. Here we show that Bt Cry1Ac protoxin interacts with the gut microbiota to accelerate the mortality of P. xylostella larvae. Cry1Ac protoxin was found to cause a dynamic change in the midgut and hemocoel microbiota of P. xylostella, with a significant increase in bacterial load and a significant reduction in bacterial diversity. In turn, loss of gut microbiota significantly decreased the Bt susceptibility of P. xylostella larvae. The introduction of three gut bacterial isolates Enterococcus mundtii (PxG1), Carnobacterium maltaromaticum (PxCG2), and Acinetobacter guillouiae (PxCG3) restored sensitivity to Bt Cry1Ac protoxin. We also found that Cry1Ac protoxin and native gut microbiota can trigger host midgut immune response, which involves the up-regulation of expression of Toll and IMD pathway genes and most antimicrobial peptide genes, respectively. Our findings further shed light on the interplay between insect gut microbiota and host immunity under the Bt toxin killing pressure, and this may provide insights for improving the management of Bt resistance and lead to new strategies for biological control of insect pests.

Identification and application of bacterial volatiles to attract a generalist aphid parasitoid: from laboratory to greenhouse assays.

Recent studies have shown that microorganisms emit volatile compounds that affect insect behaviour. However, it remains largely unclear whether microbes can be exploited as a source of attractants to improve biological control of insect pests. In this study, we used a combination of coupled gas chromatography-electroantennography (GC-EAG) and Y-tube olfactometer bioassays to identify attractive compounds in the volatile extracts of three bacterial strains that are associated with the habitat of the generalist aphid parasitoid Aphidius colemani, and to create mixtures of synthetic compounds to find attractive blends for A. colemani. Subsequently, the most attractive blend was evaluated in two-choice cage experiments under greenhouse conditions. GC-EAG analysis revealed 20 compounds that were linked to behaviourally attractive bacterial strains. A mixture of two EAG-active compounds, styrene and benzaldehyde applied at a respective dose of 1 μg and 10 ng, was more attractive than the single compounds or the culture medium of the bacteria in Y-tube olfactometer bioassays. Application of this synthetic mixture under greenhouse conditions resulted in significant attraction of the parasitoids, and outperformed application of the bacterial culture medium. Compounds isolated from bacterial blends were capable of attracting parasitoids both in laboratory and greenhouse assays, indicating that microbial cultures are an effective source of insect attractants. This opens new opportunities to attract and retain natural enemies of pest species and to enhance biological pest control.

Linear woody landscape elements may help to mitigate leaf surface loss caused by the cereal leaf beetle

ContextWoody semi-natural habitats serve as permanent habitats and hibernation sites for natural enemies and, through spillover processes, they play an important role in the biological control of insect pests. However, this service is also dependent on the amount and configuration of the dominating woody habitat types: linear landscape elements (hedgerows, shelterbelts), and more evenly extended plantations. Relating natural enemy action to the landscape context can help to identify the effect of woody habitats on biological control effectiveness.ObjectivesIn the Central European agricultural landscapes such as in the Hungarian lowlands, where our study took place, woody linear elements are characterised by high, while woody areal elements, mostly plantations, by low biological and structural diversity. In this study, we aimed to determine which composition and configuration of woody linear and areal habitats in the landscape may enhance the effect of natural enemy action on plant damage caused by the cereal leaf beetle (CLB, Oulema melanopus).MethodsHerbivory suppression by natural enemies was assessed from the leaf damage difference between caged and open treatments. These exclusion experiments were carried out in 34 wheat fields on plants with controlled CLB infections. The results were related to landscape structure, quantified by different landscape metrics of both woody linear and areal habitats inside buffers between 150 and 500 m radii, surrounding the wheat fields.ResultsThe exclusion of natural enemies increased the leaf surface loss caused by CLBs in all fields. Shelterbelts and hedgerows in 150–200 m vicinity of the wheat fields had a strong suppressing effect on CLB damage, while the presence of plantations at 250 m and further rather impeded natural enemy action.ConclusionsOur results indicate that shelterbelts and hedgerows may provide a strong spillover of natural enemies, thus contribute to an enhanced biological control of CLBs.

Insights from Population Genomics to Enhance and Sustain Biological Control of Insect Pests.

Biological control—the use of organisms (e.g., nematodes, arthropods, bacteria, fungi, viruses) for the suppression of insect pest species—is a well-established, ecologically sound and economically profitable tactic for crop protection. This approach has served as a sustainable solution for many insect pest problems for over a century in North America. However, all pest management tactics have associated risks. Specifically, the ecological non-target effects of biological control have been examined in numerous systems. In contrast, the need to understand the short- and long-term evolutionary consequences of human-mediated manipulation of biological control organisms for importation, augmentation and conservation biological control has only recently been acknowledged. Particularly, population genomics presents exceptional opportunities to study adaptive evolution and invasiveness of pests and biological control organisms. Population genomics also provides insights into (1) long-term biological consequences of releases, (2) the ecological success and sustainability of this pest management tactic and (3) non-target effects on native species, populations and ecosystems. Recent advances in genomic sequencing technology and model-based statistical methods to analyze population-scale genomic data provide a much needed impetus for biological control programs to benefit by incorporating a consideration of evolutionary consequences. Here, we review current technology and methods in population genomics and their applications to biological control and include basic guidelines for biological control researchers for implementing genomic technology and statistical modeling.

Ants provide biological control on tropical organic farms influenced by local and landscape factors

Multiple predator species can provide effective biological control of pest insects if predators have complementary effects. This could be the case of predatory ants in species-rich assemblages, such as in the tropics. However, predator assemblages are structured by variation in local and landscape factors. Different spatial scales can affect species interaction and consequently the biological control provided. We investigated ant suppression of pest insects in organic vegetable crops, and the role of local and landscape factors on biological control. We used a sentinel prey assay to determine the effectiveness of ant biological control on 18 organic farms in the Brazilian Federal District. Ants and other predatory groups were sampled on farms to determine natural enemy assemblage composition. Ants were the group that most contributed to the predation rates, and the other predator groups complemented the predation rates exerted by ants. The predation of sentinel prey increased 3.07-fold when ants were present. These results varied with the farming management practices employed. The species richness and occurrence were positively related to the predation rates, indicating that ant species-rich assemblage may be more relevant than single species in providing biological control. The predation exerted by ants and other predators were benefited by the abundance of predators in the landscape. Tree cover and cropped area in the landscape reduced ant predation but increased the predation exerted by other predators, because most ant species we sampled usually occur in open habitats. In conclusion, species-rich assemblages play a central role in providing biological control, and biological control provided by ants and other predators depends on local habitat management and landscape composition and therefore is a scale dependent process.

When Appearance Misleads: The Role of the Entomopathogen Surface in the Relationship with Its Host.

Currently, potentially harmful insects are controlled mainly by chemical synthetic insecticides, but environmental emergencies strongly require less invasive control techniques. The use of biological insecticides in the form of entomopathogenic organisms is undoubtedly a fundamental resource for the biological control of insect pests in the future. These infectious agents and endogenous parasites generally act by profoundly altering the host’s physiology to death, but their success is closely related to the neutralization of the target insect’s immune response. In general, entomopathogen parasites, entomopathogenic bacteria, and fungi can counteract immune processes through the effects of secretion/excretion products that interfere with and damage the cells and molecules typical of innate immunity. However, these effects are observed in the later stages of infection, whereas the risk of being recognized and neutralized occurs very early after penetration and involves the pathogen surface components and molecular architecture; therefore, their role becomes crucial, particularly in the earliest pathogenesis. In this review, we analyze the evasion/interference strategies that entomopathogens such as the bacterium Bacillus thuringiensis, fungi, nematocomplexes, and wasps implement in the initial stages of infection, i.e., the phases during which body or cell surfaces play a key role in the interaction with the host receptors responsible for the immunological discrimination between self and non-self. In this regard, these organisms demonstrate evasive abilities ascribed to their body surface and cell wall; it appears that the key process of these mechanisms is the capability to modify the surface, converting it into an immunocompatible structure, or interaction that is more or less specific to host factors.

Entomopathogenic Viruses in the Neotropics: Current Status and Recently Discovered Species

The market for biological control of insect pests in the world and in Brazil has grown in recent years due to the unwanted ecological and human health impacts of chemical insecticides. Therefore, research on biological control agents for pest management has also increased. For instance, insect viruses have been used to protect crops and forests around the world for decades. Among insect viruses, the baculoviruses are the most studied and used viral biocontrol agent. More than 700 species of insects have been found to be naturally infected by baculoviruses, with 90% isolated from lepidopteran insects. In this review, some basic aspects of baculovirus infection in vivo and in vitro infection, gene content, viral replication will be discussed. Furthermore, we provide examples of the use of insect viruses for biological pest control and recently characterized baculoviruses in Brazil.

Evaluation of potential trap plant species for the wheat bug Nysius huttoni (Hemiptera: Lygaeidae) in forage brassicas

Abstract The wheat bug Nysius huttoni is a major pest of brassica seedlings. Management of this insect currently relies on seed treatment with neonicotinoids and spraying with chlorpyrifos and pyrethroid insecticides. These practices can generate severe external costs, including human health, the environment and biodiversity. Trap cropping is one alternative option to protect brassica seedlings from N. huttoni. Trap crop species evaluated in field cage experiments were: alyssum (Lobularia maritima L. Desvauxcv. Benthamii White), wheat (Triticum aestivum L. cv. Morph), coriander (Coriandrum sativum L. cv. Santo) and clover (Trifolium repens L. cv. Nomad). These were compared with kale (Brassica oleracea L. cv. Kestrel). In open‐field experiments, alyssum (L maritima), wheat (T. aestivum) and a mixture of alyssum (L. maritima) and wheat (T. aestivum) were used. All of these were compared to kale (B. oleracea). Alyssum and wheat were the most favoured potential trap plants for N. huttoni. Results indicated that two treatments: alyssum (used as a single trap crop) or ‘alyssum plus wheat’ (a multiple trap crop), may be useful in brassica fields to protect the seedlings from N. huttoni damage. Such a trap cropping protocol potentially reduces pesticide use in forage brassicas and can also deliver multiple ecosystem services such as biological control of insect pests.

Biological controls in botanic gardens

Biological control of insect pests in horticulture is evolving rapidly but use in botanic gardens can be difficult due to the variety and extent of the plant collections held at these gardens. This paper describes examples of successful biological control of mealybug species at the Cambridge University Botanic Garden and Royal Botanic Garden Edinburgh and looks at some of the challenges to extending the use of such controls in all environments.

Alternative substrates for conidiogenesis of the entomopathogenic fungus Beauveria bassiana (Bals) Vuillemin (Deuteromycotina: Hyphomycetes).

Beauveria bassiana is a promising fungus for the biological control of insect pests. The growing costs of conidia production have raised the need to ascertain the efficiency of some low cost substrates. The aim of this study was to analyze the potential use of different raw substrates without nutritional supplement for B. bassiana conidiogenesis. Growth and sporulation were evaluated using 30 g of substrate and 0.3 μL of a conidia suspension (1 x 106 conidia/mL). After 10 days of incubation (70 ± 10% humidity and temperature (T) = 29 ± 1 °C), rice (2.00 x 106 conidia/g substrate), algaroba (2.36 x 106 conidia/g), malt A (1.22 x 106 conidia/g) and malt B (1.75 x 106 conidia/g) showed the highest levels of conidia production. The resulting conidia showed insecticidal activity higher than 80% on coconut termites. These new raw substrates may represent viable alternatives for the production of entomopathogenic fungi for use in the biological control of various insect pests.

Optimizing for taxonomic coverage: a comparison of methods to recover mesofauna from soil

Manipulating soil properties to modify the dynamics between nematodes and their natural enemies has been proposed to conserve services such as the biological control of insect pests by entomopathogenic nematodes. Many soil microarthropods including acari mites and collembola are natural enemies of nematodes; however, little is known about the naturally occurring assemblages of these two soil dwelling groups and how they might be influenced by soil conditions. A method to efficiently recover both nematodes and microarthropods from environmental samples would be helpful to characterize communities of these two groups in different habitats. Because samples of nematodes extracted from soil by sucrose centrifugation (SC) also contain soil mites, collembola, protozoans, and fungal and bacterial propagules, the efficiency of SC to recover microarthropods was compared to more conventional methods of microarthropod recovery such as heptane flotation (HF), Berlese funnels (BF), and a modified flotation Berlese method (FBF). Microarthropods were identified using an inverted microscope to class in one experiment and to order in a second. Significantly more microarthropods of all taxa were recovered by SC than with either Berlese method (BF or FBF). In total, 40% more microarthropods comprising seven orders were recovered by HF compared to SC, but the difference was not significant. Ecological indices (diversity, richness, and evenness) derived from HF and SC were congruent and significantly higher than those derived from BF. Excessive organic matter in the HF extractions, compared to those of SC, BF, and FBF, made mite detection and identification difficult and time consuming. Moreover, unlike SC, neither HF nor any Berlese method recovered nematodes. Accordingly, we found SC to be the most efficient method for microarthropod extraction, making it an ideal method for studies of communities of nematodes and many of their natural enemies in the soil.

Plant Insect Interaction And Crop Protection: A Dynamic Analysis

Integrating supporting and regulating ecosystem functions provided by several components of biodiversity into cropping systems has been prepared as a promising way to decrease agrochemical inputs and negative environmental impacts while maximizing crop productivity and food security. The co-evolutionof plants and insects in very intriguing and plays vital role in the crop protection. Plants have developed efficient mechanisms to protect them against herbivore while insects have found diverse ways of avoiding negative effects of their host plant defense mechanism. Even though many workers have attempted to studyplant - insect interaction, still our knowledge is limited. A changing climate, growing pest have given uncertain impacts on crop protection so, the present study address the key question that Is it possible to find alternative to meet these challenges by studying the plant-insect interaction and formulating integrated pestmanagement? The study was conducted at Dharapuram, Dindugal district as this area is riched with the variety of crop cultivation. The study concludes that the biological control of insect pests with natural products by the development of new plant varieties with enhanced chemical defenses should be followed forthe better crop protection.

Towards optimization of entomopathogenic nematodes for more service in the biological control of insect pests

Cost and reliability have hindered entomopathogenic nematodes (EPNs) from realizing their full market size. Research approaches continually evolve in response to these issues. They address EPN basics, but other issues are less recognized among masses working on these biocontrol agents. So, this review emphasizes on the due but less recognized roles to optimize EPN research and get better findings in nematode realm. Being almost impossible for nematologists to act united, they need to use standardized procedures which allow future reviews to be analytical and may build on them. Current atypical sampling procedures of EPNs may lead to erratic results. Comparable sampling may better enable grasping the interaction between EPN distribution and agricultural management to develop more swiftly field application techniques and can introduce EPNs’ populations to a more even distribution designed to enhance their efficacy. Functional sampling should be expanded. Furthermore, EPNs should be included in integrated pest management programs in ways that make them complimentary or superior to chemical pesticides. Further modeling of EPNs’ populations should be tried. The few transgenic methods applied in EPNs should be followed up to address non-stability of selected beneficial traits and markers of beneficial genes. Awareness-raising of more growers, cooperatives, and extensions of EPNs as bio-insecticides for both plant and livestock pests should be attempted in earnest via broad and deep training. We should better communicate and apply the positive trends and standardization in EPNs’ research. Required but less known services to optimize research in the nematode realm should further be addressed.

Growth kinetics and pathogenicity of Photorhabdus luminescens subsp. akhurstii SL0708

Photorhabdus luminescens subsp. akhurstii SL0708 (Enterobacteriaceae) is a symbiont of the entomopathogenic nematode (EPN), Heterorhabditis indica SL0708 (Nematoda: Rhabditida), used for insect pest biological control. In the present study, P. luminescens subsp. akhurstii SL0708 growth kinetic was evaluated considering growth and metabolic phases (phase I, intermediate phase, phase II), as well as pathogenicity. The study can be useful in determining bacterium feeding times in H. indica SL0708 production in liquid culture media. The logarithmic phase of the growth of bacterium was from 0 to 24 h, with a specific growth velocity of 0.21 h−1; during this phase, bacterium at metabolic phase I was detected. Maximum bioluminescence was registered at 24 h (3.437 luminescence AU). Finally, it was evidenced that the bacterial metabolic phase had an effect on the greater wax moth, Galleria mellonella L., larvae mortality rate. Moreover, biochemical tests were the same for all P. luminescens subsp. akhurstii SL0708 sampling times. This research is particularly relevant, since no reports are available on this bacterium isolate in Colombia. In the future, this will allow massive H. indica SL0708 production, because when pre-incubated with its symbiont, it provides essential nutrients for the EPNs development and reproduction.

Spider (Araneae) abundance and species richness comparison between native wildflower plantings and fallow controls in intensively managed agricultural areas

Large-scale agriculture has led to a loss of overall biodiversity and ecosystem services (e.g., biological control) within farmland. Native wildflower plantings have been used to restore ecosystem services and increase conservation measures within agricultural areas. In this study, we examined spider (Araneae) communities within small wildflower plots and fallow control plots that were primarily composed of grasses. Utilizing multiple trapping schemes (pitfalls, sweep netting, and pan trapping), spiders were found to be more abundant within the wildflower plots compared to fallow controls but species richness or Shannon–Wiener diversity indices were not different between the two habitats. The sheet web-weaving spider, Ceraticelus tibialis, (Araneae: Linyphiidae) was more abundant within the fallow controls, whereas, some spider families (Lycosidae, and Oxyopidae) were significantly more abundant in the wildflower plots. Categorizing spiders into hunting/web-building guilds showed that ambushers, space, and stalkers were significantly more abundant in the wildflower plots but low-sheet/tangle weavers were significantly more abundant in the fallow controls. Our results suggest that wildflower plantings can be a successful way to increase overall spider abundance within intensive agricultural areas and, thus, may help contribute to biological control of pest insects. However, our results also suggest wildflower plantings may not be a useful conservation tool that increases spider biodiversity within agricultural areas.

Diversity and abundance of insect pest of low land rice field in Lamahi, Dang district of Nepal

A study on diversity and abundance of insects in rice field was conducted at farmer field of Lamahi, Dang during July to October in 2019. Insects were collected using sweep net and light trap. Overall, 414 insect specimen representing 11 families and 8 orders were collected during the period. Grasshopper (23.98%) with including all species was the most abundance insect found in rice field as it followed by brown plant hopper (16.62%). Among the eight insect orders captured Orthoptera (29.16%) was the most abundance insect order followed by Homoptera (16.62%). As the diversity of insect pest in this area may responsible economic losses was found which will be useful to adapt appropriate management practices to keep them at normal area. The presence of natural enemies should conserve to enhance the natural biological control of insect pests.