Soil-dwelling Insects Research Articles

Insecticide exposure can increase burrow network production and alter burrow network structure in soil dwelling insects (Agriotes spp.)

Insecticide treated seeds are commonly used to reduce yield losses from burrowing insect damage such as wireworms. Using temporal X-ray Computed Tomography (CT) of soil-filled bioassays, we aimed to quantify changes in burrow network production and structure as a measure of wireworm behavioural change in response to three types of insecticide treated maize seed; compound X (R&D product in field trial stage of development); tefluthrin and thiamethoxam. A biopesticide alternative treatment (neem), untreated maize seed and bare soil were also investigated. Insect health outcomes were also monitored to provide toxicity/mortality data. Wireworms exposed to compound X produced greater burrow networks than untreated maize and neem treatments, similar to that in volume of those produced in bare soil. Compound X exposure also elicited the production of more complex burrow structures, a function of the number of vertices, edges and faces of a shape (V-E+F) related to the number of interconnected branches, compared to any other treatments. Compound X, tefluthrin and thiamethoxam induced mortality at greater rates than neem or untreated, suggesting all three could have potential to manage wireworm populations and reduce yield loss, but only compound X modified burrowing behaviour. With soil biopores playing an important role in soil productivity and carbon sequestration, the wider implications of this increase in burrowing activity for food security and climate change warrants further exploration.

Urban pavements as a novel habitat for wild bees and other ground-nesting insects

AbstractMunicipal authorities around the world have come to recognize the importance of making conservation and restoration a priority. Multiple urban restoration programs now foster insects and other pollinators through planting and sowing flowering plants, many of them within residential areas. But residents are not only walking next to pollinators visiting flowering sidewalk grass verges, they are also walking on top of them, nesting in the cracks and interstices of urban pavements.Combining morphological and molecular monitoring schemes, we conducted a survey of urban pavements at twelve locations across Berlin and found that pavements can foster a surprising number and quantity of soil dwelling insects—in particular wild bees and wasps. Pavements located within 200 m to an insect-friendly flower garden were covered with significantly more nests of wild bees and solitary wasps, and showed higher species richness of these groups, while the degree of sealed surfaces in the surrounding had no effect per se. This underlines the positive impact that insect-friendly gardens can have for pollinators and other insects, even in highly sealed areas. Also, it shows the potential of cobbled pavements as valuable nesting sites in highly sealed urban areas. We provide a list of 55 species of ground-nesting Hymenoptera found in Berlin pavements, including 28 species of wild bees and 22 apoid wasps. In our study, the molecular approach only detected three Hymenoptera species and did not yield comparable results to classical monitoring. Nonetheless, using eDNA methods might be a promising tool for further studying soil nesting insects in the future, and to gain insights into the web of life in urban pavements.

Bioinspired multilayer mulch film integrating mud repulsion, adhesion reduction, and antifouling for high-efficiency resource recycling

Resource recycling is a promising solution to the current problem of residual film pollution. However, the challenge that remains to be addressed in the resourcefulness of mulch films lies in mitigating heavy water and power consumption during the cleaning process. Herein, inspired by the unique structure of typical soil-dwelling insects, the mass production of high-strength multilayer mulch (Bio-HAM) films is achieved through a sequential combination of multilayer coextrusion, blow molding, roll-to-roll imprinting, and spray coating. The regular micro-nano hierarchical structure on the Bio-HAM films surface enables it to effectively inherit the antifouling, slurry repulsion, and adhesion reduction functions of the prototypes, even when exposed to ultraviolet radiation, deformation, and liquid or solid impact. Benefiting from the aforementioned properties, the Bio-HAM films exhibit low impurities adhering and soil wrapping during the entire planting cycle. The impurity content of the recovered Bio-HAM films wrapping is approximately 12.7 g/m2, which is a 67.4% reduction in impurity content compared to the basic films. Moreover, the recovered film also possesses favorable mechanical and thermal properties, thereby ensuring water and energy conservation as well as high-value regeneration. The proposed approach is expected to address the excessive consumption and persistent ecological pollution of residual film recycling.

Eliminating explanations for Maladera formosae (Coleoptera: Scarabaeidae) preponderance in sandy soil.

Most field corn in the United States receives a neonicotinoid seed treatment for the management of early-season, soil-dwelling insect pests. Grubs of Maladera formosae (Brenske) (Coleoptera: Scarabaeidae) have been reported feeding on young field corn with both low and high rates of clothianidin seed treatments in Indiana, Michigan, and Ohio. Anecdotally, these infestations are restricted to sandy soils in the region. The purpose of this study was to (1) evaluate whether grub populations in corn are restricted to sandy soils, (2) assess whether soil type influences M. formosae survival, and (3) determine whether soil type affects clothianidin uptake by the plant, possibly explaining the observed differences in M. formosae abundance by soil type. We observed nearly 10-times more grubs in sand (>80% sand content) than loam (<80% sand content) soil within a single corn field. Grub survival to adult was not influenced by soil type. We then compared the concentrations of clothianidin seed treatment in the roots and shoots of corn seedlings grown in either sand or loam soil over time. Similar amounts of the active ingredient were found in the roots and shoots of corn grown in both soil types. Within 2 week, the clothianidin concentrations in both soil types had significantly declined in roots and shoots and were no different from the no-insecticide control. These findings suggest that factors other than insecticide exposure contribute to the higher abundance of M. formosae larvae in sand relative to loam soils, even within the same field.

Development of underground detection system using a metal detector and aluminum tag for, Copris ochus (Coleoptera: Scarabaeidae).

Tracking of soil-dwelling insects poses greater challenges compared to aboveground-dwelling animals in terrestrial systems. A metal detector system consisting of a commercially available detector and aluminum tags was developed for detecting dung beetle, Copris ochus Motschulsky(Coleoptera: Scarabaeidae). First, detection efficacy of the system was evaluated by varying volumes of aluminum tags attached on a plastic model of the insect and also by varying angles. Then, detection efficacy was evaluated by varying depths of aluminum-tagged models under soil in 2 vegetation types. Finally, the effects of tag attachment on C. ochus adults were assessed for survivorship, burrowing depth, and horizontal movement. Generally, an increase in tag volume resulted in greater detection distance in semi-field conditions. Maximum detection distance of aluminum tag increased up to 17cm below soil surface as the tag size (0.5 × 1.0cm [width × length]) and thickness (16 layers) were maximized, resulting in a tag weight of 31.4mg, comprising ca. 9% of average weight of C. ochus adult. Furthermore, the detection efficacy did not vary among angles except for 90°. In the field, metal detectors successfully detected 5 aluminum-tagged models in 20 × 10 m (W × L) arena within 10min with detection rates ≥85% for up to depth of 10cm and 45%-60% at depth of 20cm. Finally, aluminum tagging did not significantly affect survivorship and behaviors of C. ochus. Our study indicates the potential of metal detector system for tracking C. ochus under soil.

Trap crops enhance the control efficacy of Metarhizium brunneum against a soil-dwelling pest

Soil-dwelling insect pests may cause considerable damage to crops worldwide, and their belowground lifestyle makes them hard to control. Amongst the most promising control agents for subterranean pests are soilborne entomopathogenic fungi (EPF) such as Metarhizium brunneum. Albeit EPF can be highly pathogenic to their target pest species under laboratory conditions, their efficacy in the field is often limited due to adverse environmental conditions. Here, we test for the first time if the efficacy of EPF can be improved when they are augmented with trap crops. In a field experiment, the M. brunneum strain ART2825 was combined with a trap crops mixture of six plant species and evaluated for its control effect of wireworms (Coleoptera: Elateridae). When both were combined in the main crop, potato damage was lowered on average by 42.5% and wireworm abundance by 50.8%. Single application of trap crops or EPF lowered damage/pest abundance only by 29.9%/15.89% and 34.7%/4.77%, respectively. Importantly, the strength of the synergistic pest control effect between trap crops and EPF increased disproportionately with increasing wireworm abundance. However, DNA-based gut content analysis showed that wireworms’ feeding preferences were not shifting toward the trap crops. Our findings demonstrate that combining trap crops with EPF improves the efficacy of the latter and leads to a synergistic control effect which magnifies with increasing wireworm abundance. Hence, the synergistic effect of EPF and trap crops might be a promising control strategy for soil-dwelling pests in general and significantly improve our abilities to manage soil pests environmentally friendly.

Harvest load transfer sites influence sugarcane billbug (Coleoptera: Curculionidae) spatiotemporal injury in sugarcane.

The sugarcane billbug, Sphenophorus levis Vaurie 1978, is a key soil-dwelling insect pest of sugarcane in Brazil and greatly affects plant development and yield. This insect presents an aggregated distribution pattern in production fields. The reasons for such behavior include intraspecific communication and attractivity due to the fermentation of sugar in stalk residues. During mechanized harvesting, part of the harvested material usually falls in the load transfer sites, becoming a potential source for increasing the infestation. We therefore evaluated whether producing areas near the harvest load transfer sites are more prone to S. levis injury. There are greater chances of finding billbug injury within a radius of 740 m from the harvest load transfer site. Additionally, injured areas are estimated to expand 11.96% each growing season. Our spatiotemporal models support higher injured areas surrounding the harvest load transfer site and show clear and significant signs of increased injury levels compared to the initial growing season surveyed. Our results reinforce the importance of harvest transfer sites in the dispersion and propagation of the sugarcane billbug. Based on this knowledge, sugarcane millers and growers can adopt preventive and remedial practices within the loading sites that can potentially contribute to the successful management of this insect pest. © 2023 Society of Chemical Industry.

Host-foraging strategies of five local entomopathogenic nematode species in South Africa

Entomopathogenic nematodes (EPNs) are obligate parasites of soil-dwelling insects and are used as biological control agents for many insect pests. These nematodes have a free-living third growth stage called infective juveniles (IJs), which are responsible for foraging and infecting suitable insect hosts. Infective juveniles exhibit three host-foraging strategies: cruising, ambushing, and intermediate foraging strategies. The foraging strategy of EPNs is important for successful infection but is poorly understood. The current study investigated the host-foraging strategies of five local South African EPN species including Heterorhabditis noenieputensis, H. safricana, Steinernema fabii, S. jeffreyense, and S. yirgalemense by assessing their dispersal behavior. Of the five EPN species, H. noenieputensis, H. safricana, S. jeffreyense, and S. yirgalemense showed a positive response to the presence of the wax moth larvae, whereas S. fabii showed a negative response. The four EPN species that showed a positive response to the presence of the host also caused 100% mortality of wax moth larvae that were buried in sand at a depth of 10 cm, whereas S. fabii caused the lowest mortality of 34%. The average distance traveled by all five EPN species decreased on rough textured substrate compared with smooth textured substrate. The observed behavioral patterns suggested that H. noenieputensis, H. safricana, S. jeffreyense, and S. yirgalemense use a cruiser foraging strategy whereas S. fabii uses an ambusher foraging strategy.

Biocontrol potential of native entomopathogenic nematodes against Gonioctena fornicata (Brüggemann, 1873) (Coleoptera, Chrysomelidae) in alfalfa

BackgroundGonioctena fornicata (Brüggemann, 1873) (Coleoptera: Chrysomelidae) inflicts substantial crop damage by consuming alfalfa leaves. The main aim of the study was to develop an efficient, sustainable control method against the pest, considering entomopathogenic nematodes (EPNs) as a potential control agent against soil-dwelling insect pests. This study investigated the impact of two native entomopathogenic nematodes (EPNs), Heterorhabditis bacteriophora (isolate Z-1) and Steinernema feltiae (isolate A-16), on mature larvae and adults of G. fornicata. Concentrations of 250, 500, and 1000 IJs/ml were used for adult and larval stages, and mortality rate was determined at the end of 144 h for larvae and 240 h for adults.ResultsThe highest effect was 94.7% at 120 h for isolate Z-1 and 91.0% at 168 h for isolate A-16 at a concentration of 1000 IJs/ml for adult stages. The highest effect on larval stage was 97.6% at 96 h for isolate Z-1 and 85.8% at 120 h for isolate A-16 at the concentration of 1000 IJs/ml. On the adult stage, isolate Z-1 showed 50.0–67.1% effect at concentrations of 250 and 500 IJs/ml, respectively, while isolate A-16 showed an effect ranging from 46.7 to 63.6%. In the larval stage, isolate Z-1 caused 39.7–77.6% mortality at 250 and 500 IJs/ml concentrations, respectively, while the rate was 32.9–63.9% for isolate A-16. In the trial, isolate Z-1 showed a high efficacy in both stages of G. fornicata.ConclusionsThis study represents the first laboratory investigation encompassing both adult and mature larval stages of G. fornicata. The obtained data offer valuable insights for alternative control strategies targeting G. fornicata.

Burkholderia spp.-based biopesticide controls wireworms (Coleoptera: Elateridae) in potatoes.

Wireworms (Coleoptera: Elateridae) are economically significant pests of potatoes (Solanum tuberosum), damaging the marketable portion of the crop by feeding and tunneling into tubers. While conventional potato growers use the few registered synthetic insecticides to control wireworms, certified organic growers are left with less options due to the limited effectiveness of the available insecticides. Biologically derived pesticides provide an additional alternative for both systems. Certain gram-negative proteobacteria, such as Burkholderia spp., possess insecticidal compounds. However, very little is known about their efficacy on wireworms. From 2018 to 2021, we conducted experiments in Virginia to assess the efficacy of a Burkholderia spp.-based commercial pesticide, Majestene, as a wireworm control in potatoes. In a lab experiment, soil drench application of this insecticide at a rate of 66 g a.i. per 1 liter resulted in 30% wireworm mortality and significantly reduced wireworm feeding damage on potato tubers. In the field, in-furrow applications of Burkholderia spp. at a rate of 17.66 kg a.i. per ha significantly reduced wireworm damage to tubers in 2 of 7 field experiments conducted. By comparison, the commercial standard insecticide, bifenthrin, significantly reduced tuber damage in 3 of the 7 field experiments. Our study demonstrates the prospect for proteobacteria-derived insecticides for control of wireworms and potentially other soil-dwelling insects. In conclusion, findings present growers with another option to combat wireworm pressure, especially in organic systems.

An alginate-based encapsulation enhances shelf life and bioactivity of the entomopathogenic fungus, Metarhizium anisopliae

BackgroundThis study evaluated the shelf life and effectiveness of Metarhizium anisopliae encapsulated in Na (sodium)-alginate matrix. Air-flow-dried and freeze-dried beads containing conidia of M. anisopliae produced in submersion in the liquid broth were fabricated and characterized. Shelf life and efficacy of fabricated beads against three species of the white grubs, namely Holotrichia serrata, Adoretus sp., and Lepidiota mansueta, were evaluated under greenhouse conditions.ResultsThe mean size of the wet beads ranged between 1.4 and 3.2 mm. The mean size of beads that were dried through freeze drying ranged between 0.55 and 2.3 mm. However, the mean size of beads dried through air flow ranged between 0.55 and 2.35 mm. Viability of M. anisopliae was more in freeze-dried beads stored at 8 °C compared to air-flow-dried beads with 20.0 × 107 and 16.00 × 107 CFU/g, respectively, after two weeks of drying. Further, freeze-dried beads supported M. anisopliae conidial viability till 10 months with 2.0 × 107 CFU/g. The LC50 values of the freeze-dried beads with M. anisopliae after 21 days of treatment were 0.35 (2.1 × 108 CFU/g), 0.31 (2.1 × 108 CFU/g), and 0.76 mg (2.1 × 108 CFU/g) against H. serrata, Adoretus sp., and L. mansueta, respectively.ConclusionThe results of this study support the use of Na-alginate beads followed by freeze drying to maintain the viability of M. anisopliae. The effectiveness of freeze-dried beads with M. anisopliae against white grubs indicates that these beads can be an alternative option of synthetic insecticides against soil dwelling insect pests. In addition, this study offers a steppingstone for further advancement of sodium alginate encapsulated formulations for soil insect control.

Curative efficacy of entomopathogenic nematodes against white grubs in honeysuckle fields

Root-feeding white grubs are one of the most serious pests of honeysuckle trees (Lonicera japonica) in China, directly damaging their roots and facilitating infection by soil pathogens. Entomopathogenic nematodes (EPNs) are considered as potential control agents against soil-dwelling insect pests. This study aimed to identify effective EPN species against white grubs through bioassay and field experiments. Among the EPN species screened against Holotrichia oblita under laboratory conditions, Steinernema feltiae and Heterorhabditis indica had low virulence, while S. longicaudum, S. glaseri, and H. bacteriophora applied at a rate of 400 IJs/larva caused a higher corrected mortality (80.00 ± 5.77%), which screened them as good candidates for future applications. The field experiments showed that both S. longicaudum and H. bacteriophora were approximately as effective in reducing white grubs as the insecticide phoxim, whereas S. glaseri caused a significantly lower reduction compared with these two EPNs and phoxim. Plant mortalities obtained from S. longicaudum, H. bacteriophora and the insecticide treatment plots were significantly lower than those observed in the water-treated control plots. All EPNs examined could establish well in the treated honeysuckle fields for 42 d, confirmed by Tenebrio molitar larvae baiting technique. Our findings suggest that EPNs could provide curative efficacy against white grubs and significantly reduce plant death in honeysuckle fields.

Rattus norvegicus (Berkenhout, 1769) (Rodentia: Muridae)’un entomopatojen bakteriler ile enfekte böcek kadavralarına tepkisinin belirlenmesi

Xenorhabdus Thomas &amp;amp; Poinar (Enterobacterales: Morganellaceae) and Photorhabdus Thomas &amp;amp; Poinar (Enterobacterales: Morganellaceae) bacteria are mutualistically associated with Steinernema Travassos, 1927 (Rhabditida: Steinernematidae) and Heterorhabditis Poinar, 1976 (Rhabditida: Heterorhabditidae) nematodes, respectively, and are known to produce several secondary metabolites that protect nematode-killed insects from different competitors. One of these compounds called “the scavenger deterrent factor” (SDF) is known to deter different arthropod, bird, and fish species from feeding on insects killed by Xenorhabdus or Photorhabdus bacteria. The effects of SDF from five different Xenorhabdus and one Photorhabdus species against the Norway rat, Rattus norvegicus (Berkenhout, 1769) (Rodentia: Muridae) were investigated using either a one-choice or two-choice experimental design during 2019-2020 in Aydın Adnan Menderes University. Rats were given four-day-old bacteria-killed Galleria mellonella (L., 1758) (Lepidoptera: Pyralidae) larvae and feeding behavior was observed and recorded. The results demonstrate that the Norway rat is deterred from feeding on insects killed by certain Xenorhabdus and Photorhabdus species and it is likely due to the distastefulness of these cadavers. Ecologically, the data suggest that insects killed by the entomopathogenic nematode/bacterium complex in nature may be protected from attack from insectivorous mammals, especially those that feed on soil-dwelling insects.

Evaluation of Entomopathogenic Nematodes against Common Wireworm Species in Potato Cultivation

Wireworms (Coleoptera: Elateridae) are common insect pests that attack a wide range of economically important crops including potatoes. The control of wireworms is of prime importance in potato production due to the potential damage of the larvae to tuber quantity and quality. Chemical insecticides, the main control strategy against wireworms, generally fail to provide satisfactory control due to the lack of available chemicals and the soil-dwelling habits of the larvae. In the last decades, new eco-friendly concepts have emerged in the sustainable control of wireworms, one of which is entomopathogenic nematodes (EPNs). EPNs are soil-inhabitant organisms and represent an ecological approach to controlling a great variety of soil-dwelling insect pests. In this study, the susceptibility of Agriotes sputator Linnaeus and A. rufipalpis Brullé larvae, the most common wireworm species in potato cultivation in Türkiye, to native EPN strains [Steinernema carpocapsae (Sc_BL22), S. feltiae (Sf_BL24 and Sf_KAY4), and Heterorhabditis bacteriophora (Hb_KAY10 and Hb_AF12)] were evaluated at two temperatures (25 and 30 °C) in pot experiments. Heterorhabditis bacteriophora Hb_AF12 was the most effective strain at 30 °C six days post-inoculation and caused 37.5% mortality to A. rufipalpis larvae. Agriotes sputator larvae were more susceptible to tested EPNs at the same exposure time, and 50% mortality was achieved by two EPNs species, Hb_AF12 and Sc_BL22. All EPN species/strains induced mortality over 70% to both wireworm species at both temperatures at 100 IJs/cm2, 18 days post-treatment. The results suggest that tested EPN species/strains have great potential in the control of A. sputator and A. rufipalpis larvae.

Effects of Three Different Tillage Patterns on Ground and Below-Ground Dwelling Insect Assemblage

Tillage could significantly change the biodiversity in farmlands. As a prominent component of farmland ecology, crops play a key role in regulating biological communities. To explore the effects of tillage patterns and planting modes, including high-disturbance tillage practices and different plant compositions, on the abundance of soil insects, we tested the responses of soil insects to no-tillage (NT), ridge tillage (RT), and fall plow (FP) treatments with different planting modes. The results illustrated that planting modes significantly changed the distributions of ground-dwelling insect species and disturbed interactions on the farmland. Soil-dwelling insect assemblages were mainly influenced by tillage patterns, which reflected that soil physicochemical properties, especially pH, had the highest contribution to the determination of community composition. The no-tillage system supported the highest predator species richness and lower herbivore richness with higher abundance. In the no-tillage system, most of the insects on the farmland have established relationships, forming a relatively high degree of connection between different insects. The network was more specialized and nested in the field with fall ploughing. In conclusion, the effects of tillage patterns and planting modes on insect assemblage can be divided into two spatial dimensions: the success of soil-ground insect maintenance determined by plants and below-ground depended on tillage.

Natural occurrence of entomopathogenic nematodes (Steinernema and Heterorhabditis) and Pristionchus nematodes in black truffle soils from Spain.

The European truffle beetle Leiodes cinnamomeus is the most important pest in black truffle (Tuber melanosporum) plantations. Current control methods against it are inefficient, so entomopathogenic nematodes (EPNs) could play an important role in their population regulation due to their efficacy against many soil-dwelling insect pests. A survey of EPNs and Pristionchus nematodes was conducted in truffle soils of Spain, considering environmental and physical-chemical soil factors. A total of 164 soil samples were collected from forests, productive plantations and null-low productive plantations, representing three distinct black truffle-growing habitat types. EPNs were isolated from seven soil samples (4.3%); four nematodes were identified as Steinernema feltiae and three as Heterorhabditis bacteriophora. Both species were sampled in three types of soil texture (loam, sandy loam or sandy clay loam), characterized by alkaline pH (7.5 to 8.5) and high organic matter (2.1-11.04%). The presence of these EPNs was influenced by habitat type and organic matter content. Pristionchus nematodes were isolated from truffle soil, around truffle fruit bodies and under the elytra of L. cinnamomeus, with Pristionchus maupasi being the most commonly identified species. No significant associations were found between environmental and soil factors and the occurrence of Pristionchus nematodes. These nematodes were found in alkaline soils (pH 7.75 to 8.7), across all seven sampled soil textures, with variable organic matter content (0.73%-5.92%). The ecological trends and the presence of Pristionchus may affect the occurrence of EPNs and their prospective use as biological control agents against L. cinnamomeus in black truffle plantations.

A decision support system based on Bayesian modelling for pest management: Application to wireworm risk assessment in maize fields

Protecting crops against pests is a major issue in the current agricultural production system. In particular, assessing the risk to crops can promote integrated pest management (IPM) strategies that encourage natural control mechanisms and advocate the use of pesticides as a last resort. In this study, we focused on wireworms, major soil-dwelling insect pests inflicting severe economic damage on various crops (including maize, potatoes and cereals) across Europe and North America. We have developed an original hierarchical Bayesian model that explicitly accounts for biological knowledge and uncertainty in field observations, rather than relying solely on statistical correlations, to predict the level of wireworm infestation. The model was calibrated and validated using a substantial dataset originating from an agro-environmental survey carried out over three consecutive years (2012–2014) in France, which provides the wireworm abundance in 419 maize fields, together with information on the landscape context, field history, weather conditions, soil characteristics and farming practices associated to each field. Model outcomes show good agreement with current knowledge from literature and field expertise in terms of the effects of variables on wireworm abundance, and provide fairly good predictive capacity. Subsequently, the model was encapsulated as a software (R shiny application) to predict the risk of wireworm infestation in any field of interest, and can be used by farmers or agricultural advisors as a decision support system for the implementation of IPM strategies. The conceptual framework that we implemented can be adapted to a wide range of similar situations involving other crops and pests.

Capsule-C: an improved Steinernema carpocapsae capsule formulation for controlling Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae)

BackgroundEntomopathogenic nematodes (EPNs) have long been used for controlling soil-dwelling insects. Steinernema carpocapsae HB310, previously showed a high virulence against many pests including Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae). Due to the lack of durable formulations, up until now, S. carpocapsae HB310 has thus far been prevented from use in large-scale farming. The present study aimed to get a better EPNs capsule formulation suitable for long-term storage and effective application.ResultsAn improved EPNs capsule formulation, herein named: Capsule-C was prepared by the following composition: Solution I: 18% glycerol, 0.075% formaldehyde, 1% sodium alginate, 0.2% xanthan gum, 0.5% potassium sorbate, 9% glucose, 2% fructose, 2% sucrose, and the remainder was distilled water. The nematodes suspension was added to the alginate mixture in 2 × 104 IJs/mL; Solution II: 18% glycerol, 0.075% formaldehyde, 0.5% calcium chloride, 0.5% potassium sorbate, with the remainder being distilled water. After storage for 180 days at 16 °C and 100% RH, the survival rate of nematodes in Capsule-C was 75.68 ± 0.48% and the nematodes caused 82.33 ± 1.45% mortality in the 5th instar larvae of Galleria mellonella. A. ipsilon larvae preferred to chew and ingest Capsule-C due to the addition of the glucose compound. The feeding rate of A. ipsilon larvae on Capsule-C reached to 100% within 24 h and the larval mortality of A. ipsilon was 90.48 ± 6.35%.ConclusionEPNs-containing capsules were as effective as sprayed EPNs in water solution at killing A. ipsilon. These results will provide ideas to acquire a stable and efficient EPNs capsule formulation and further promote the application of environmental friendly biological pesticides.

Positioning entomopathogenic nematodes for the future viticulture: exploring their use against biotic threats and as bioindicators of soil health

Vineyards face several biotic threats that compromise the grape quality and quantity. Among those that cause relevant economic impact and have worldwide distribution are the oomycete Plasmopara vitícola, the fungi Erysiphe necator and Botrytis cinerea, and the arthropods Lobesia botrana, Tetranychus urticae, and Phylaenus spumarius (principal vector of the bacterial disease Xylella fastidiosa in Europe). Their management relies primarily on agrochemicals with short persistence; widespread use of these chemicals causes environmental and human health problems. The challenge of sustainable viticulture is to provide ecologically sound alternatives. In this regard, the application of entomopathogenic nematodes (EPNs) and natural products derived from their symbionts can be an alternative. EPNs are well-known biocontrol agents for soil-dwelling insects. However, current research demonstrates the great potential of both EPN and their derivates as direct bio-tools against some of the key fungal and arthropods pests present aboveground. In addition, recent evidence shows that detecting EPN presence and activity and their relation with other soil organisms associated with them can help us to understand the impact of different agricultural practices on vineyard management. Altogether, this review illustrates the great potential of EPN to enhance pest and disease management in the next generation of viticulture.

SOIL-INSECT toolbox: A new chamber for analysing the behaviour of herbivorous insects and tri-trophic interactions in soil

A chamber, named SOIL-INSECT toolbox, was developed to analyse the effect of various factors on the behaviour of soil-dwelling insects. It is equipped with sensors that continuously monitor the concentration of CO2 in the different compartments of the chamber without disturbing the air balance in the soil. The chamber can be adapted to study different stimuli, including volatile compounds, both in the presence and absence of plants. The chamber was tested using the larvae of Melolontha spp., which confirmed its suitability for carrying out complex studies on insect-insect and insect-plant-microbiome interactions in a complex environment such as soil. The results of behavioural experiments using L3 larvae of Melolontha spp. in sterilized and natural soils revealed that the soil condition affected the behaviour of the larvae, likely due to its effect on the soil microbiome and physico-chemical characteristics.