Soil-dwelling Insect Pests Research Articles

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.

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.

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.

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.

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.

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.

Can the botanical azadirachtin replace phased-out soil insecticides in suppressing the soil insect pest Diabrotica virgifera virgifera?

BackgroundDue to recent bans on the use of several soil insecticides and insecticidal seed coatings, soil-dwelling insect pests are increasingly difficult to manage. One example is the western corn rootworm (Diabrotica virgifera virgifera, Coleoptera: Chrysomelidae), a serious root-feeder of maize (Zea mays). We investigated whether the less problematic botanical azadirachtin, widely used against above-ground insects, could become an option for the control of this soil insect pest.MethodsArtificial diet-based bioassays were implemented under standard laboratory conditions to establish dose response curves for the pest larvae. Then, potted-plant experiments were implemented in greenhouse to assess feasibility and efficacy of a novel granular formulation of azadirachtin under more natural conditions and in relation to standard insecticides.ResultsBioassays in three repetitions revealed a 3-day LD50 of 22.3 µg azadirachtin/ml which corresponded to 0.45 µg/neonate of D. v. virgifera and a 5-day LD50 of 19.3 µg/ml or 0.39 µg/first to second instar larva. No sublethal effects were observed. The three greenhouse experiments revealed that the currently proposed standard dose of a granular formulation of 38 g azadirachtin/hectare for in-furrow application at sowing is not enough to control D. v. virgifera or to prevent root damage. At 10× standard-dose total pest control was achieved as well as the prevention of most root damage. This was better than the efficacy achieved by cypermethrin-based granules and comparable to tefluthrin-granules, or thiamethoxam seed coatings. The ED50 for suppressing larval populations were estimated at 92 g azadirachtin/ha, for preventing heavy root damage 52 g/ha and for preventing general root damage 220 g/ha.ConclusionsThere seems clear potential for the development of neem-based botanical soil insecticides for arable crops such as maize. They might become, if doses are increased and more soil insecticides phased out, a promising, safer solution as part of the integrated pest management toolkit against soil insects.

Characterisation of the complete mitochondrial genome of the insect-parasitic nematode Heterorhabditis bacteriophora: an idiosyncratic gene order and the presence of multiple long non-coding regions

Summary We present here the complete mtDNA genome (mitogenome) of Heterorhabditis bacteriophora, an important biological control agent of soil-dwelling insect pests in agriculture and horticulture. This is the first description of a mitogenome for a member of the family Heterorhabditidae. The genome contains the typical chromadorean complement of 12 protein-coding genes, 22 tRNA genes and two rRNA genes. All genes are transcribed in the same direction and have a nucleotide composition high in A and T. For the entire genome, the nucleotide contents are 47.02% (T), 28.81% (A), 16.10% (G), 8.08% (C) and 75.83% (AT). Heterorhabditis bacteriophora has a unique, idiosyncratic gene arrangement. It differs from that of Caenorhabditis elegans in having a block of seven genes: trnQ-trnF-cytb-trnL1-cox3-trnT-nad4 translocated to a position between nad3 and nad5, as well as having a change in the position of the four tRNA block gene cluster, trnC-trnM-trnD-trnG, where trnC and trnM have switched places and trnD and trnG have translocated between nad4 and nad5 genes. The H. bacteriophora mitogenome is 18 128 bp long, and thus is ca 4 kb larger than the mitogenomes of most chromadoreans. This relatively large genome is due to the presence of five non-coding regions (NCR): NCR1 (114 bp), NCR2 (159 bp), NCR3 (498 bp), NCR4 (1917 bp) and NCR5 (2154 bp), which make up 26.7% of the genome. The NCR5 had the highest A + T content of 83.47% indicating that this region is the likely AT-rich control region. The complete 498 bp NCR3 sequence is duplicated in NCR4 and in NCR5 (the putative AT-rich control region). Such an organisation has not been reported previously in nematode mtDNA.

Native Philippine Heterorhabditis indica isolates from banana and rice fields and preliminary results of their virulence against the larvae of super worm (Zophobas morio Fabricius Coleoptera: Tenebrionidae)

BackgroundEntomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae are used as biological control agents of several insect pests in lieu of synthetic pesticides.ResultsUsing an insect-baiting technique, naturally occurring EPN isolates were collected from banana and rice fields in the municipality of Hagonoy, the Philippines. A total of 4 isolates were recovered from all the sites namely, HBP1, HBP2, HR3 and HR4. By combining morphometrical and ITS rDNA data, all the isolates were identified as Heterorhabditis indica. To initially assess their infectivity, virulence tests were conducted on the last instar larvae of the super worm, Zophobas morio Fabricius (Coleoptera: Tenebrionidae), the model insect. HR3 isolate had the highest percentage mortality (56%), followed by HBP1 and HBP2 (33%), which were comparable to the available nematode in the market, Heterorhabditis bacteriophora (44%), whereas the lowest was obtained in HR4 isolate (11%).ConclusionsThis study accounted 4 more H. indica isolates in addition to pre-existing isolates in the country, expanding its habitat range and geographic distribution. This also provides baseline information on the potential biocontrol utilization of native EPNs against soil-dwelling insect pests of agricultural crops. Further investigations are required to assess their efficacy against several other insect pests of economic importance for the integrated pest management (IPM) programmes in the country.

Limoniic Acid - Major Component of the Sex Pheromones of the Click Beetles Limonius canus and L. californicus.

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are soil-dwelling insect pests inflicting major economic damage on many types of agricultural crops worldwide. The objective of this work was to identify the female-produced sex pheromones of the Pacific Coast wireworm, Limonius canus LeConte, and the sugarbeet wireworm, L. californicus (Mannerheim) (Coleoptera: Elateridae). Headspace volatiles from separate groups of female L. canus and L. californicus were collected on Porapak Q and analyzed by gas chromatography with electroantennographic detection (GC-EAD) and GC-mass spectrometry. GC-EAD recordings revealed strong responses from male L. canus and male L. californicus antennae to the same compound, which appeared below GC detection threshold. The structure of this candidate pheromone component was deduced from the results of micro-analytical treatments of extracts, retention index calculations on four GC columns, and by syntheses of more than 25 model compounds which were assessed for their GC retention characteristics and electrophysiological activity. The EAD-active compound was identified as (E)-4-ethyloct-4-enoic acid, which we name limoniic acid. In field experiments in British Columbia and Alberta, Canada, traps baited with synthetic limoniic acid captured large numbers of male Limonius click beetles, whereas unbaited control traps captured few. Compared to traps baited with the analogue, (E)-5-ethyloct-4-enoic acid, traps baited with limoniic acid captured 9-times more male L. californicus, and 6.5-times more male western field wireworms, L. infuscatus Motschulsky, but 2.3-times fewer male L. canus. Limoniic acid can now be developed for detection, monitoring and possibly control of L. californicus, L. infuscatus and L. canus populations.

Dynamic role of grasslands as sources of soil-dwelling insect pests: New insights from in silico experiments for pest management strategies

Sustainable pest control strategies hinge on the knowledge of movement ecology within the agricultural landscape where contrasted habitat qualities intermingle, thereby influencing arthropod dispersal. Hence, habitat manipulation in space and time can be a lever for action to control pests with regard to landscape compositional constraints. In this study, we examined the role of grassland arrangements in field colonisation by soil-dwelling pests within a dynamic agricultural landscape, and discussed the implications for pest management with a focus on wireworms. For this purpose, we proposed a framework combining (i) a spatially explicit and mechanistic model describing the pest population dynamics in both aerial and soil compartments involved along its life cycle, and (ii) spatiotemporal representations of various landscape contexts. We addressed the role of grassland in plot history, in plot neighbourhood, or in both history and neighbourhood. Our results show that species with a short life cycle are more responsive to changes in land use, and that the neighbourhood effect strongly relies on dispersal mechanisms (random vs directed movements). We also highlight how the arrangement of grassy landscape elements in space and time can mitigate crop infestation by soil-dwelling pests, thereby emphasizing the relevance of managing grassland regimes. Once informed by critical pest life traits, our approach opens avenue for the exploration of the spatiotemporal land use manipulation meant for pest management. Future research consists in the exploration of suppressive patterns in simplified but realistic agricultural landscapes, generated under agronomic constraints at the farm or landscape scales.

The effect of vineyard groundcover on the abundance of naturally occurring entomopathogenic fungi isolated using a quantitative Galleria bait method

Although sold commercially as myco-insecticides, naturally occurring soil borne entomopathogenic fungi (EPF) pose a unique opportunity for regulating soil-dwelling insect herbivore populations via conservation biological control. Plant identity has a significant effect on soil borne fungi, which may includee EPF. We asked whether the choice of covercrops could affect the diversity and infectivity of EPF in a vineyard. We studied the effect of different mixtures of groundcover vegetation on the infectivity and community composition of the naturally occurring EPF community in a semi-arid vineyard in British Columbia, Canada. Soil was collected from a groundcover field trial and used in a quantitative laboratory bioassay with the model insect, Galleria mellonella. Death by mycosis was greater when Galleria was exposed to soil collected from groundcovers containing native versus exotic grasses. EPF communities isolated from Galleria cadavers also differed among groundcovers. This study presents the first evidence that manipulating vegetative identity can alter the composition and infectivity of soil-dwelling EPF. Future work should investigate the potential for groundcovers and cover crops to increase conservation biological control of soil-dwelling insect pests via changes to EPF communities in specific crop-pest scenarios.

Influence of Groundcover Vegetation, Soil Physicochemical Properties, and Irrigation Practices on Soil Fungi in Semi-arid Vineyards

Although plants are known to have a strong influence on soil biota, the effect of groundcover vegetation in perennial cropping systems on soil fungi has been little explored. We surveyed extensively managed vineyards to determine how plant community functional characteristics, soil factors, and irrigation management related to the abundance of two guilds of soil fungi that may play a role in plant-soil feedback (entomopathogenic fungi represented by Beauveria bassiana, and the pathogenic species complex, Ilyonectria spp.). We found that plant community characteristics were related to fungal abundance for both fungi assayed. Beauveria bassiana increased with native species, annual plants, and legumes consistently across sampling periods. Ilyonectria spp. increased with the abundance of forbs and exotic species, though only the relationship with forbs was consistent across sampling periods. Both fungal guilds increased with increasing soil organic matter. The use of dual or sprinkler irrigation systems also increased Beauveria bassiana and Ilyonectria spp. in vineyard soils. Overall, groundcover vegetation played a significant role in driving abundance of these important groups of soil fungi. Groundcover management may therefore be a viable tool to manipulate soil fungi with the potential for improving ecosystem services such as conservation biological control of soil dwelling insect pests and deterring pathogens in perennial cropping systems.

Effects of several ingredients on in vitro mass production of Heterorhabditis bacteriophora HBH strain

Biological control is a great alternative to chemical pesticides in agriculture. Entomopathogenic nematodes (EPNs) are environmentally safe biocontrol agents that are used mostly against soil-dwelling insect pests. EPNs have been commercially mass produced for several decades. Mass production is generally done in vitro using solid and liquid cultures. After mass production, they are formulated with filler compounds and sold as commercial products. Most common substances for in vitro production are nutrient broth, yeast extract, soyflour and different plant oils for protein and lipid source. To increase the production yield of the mass culture, several compounds can be added to the media. In this study; lecithin, egg yolk and the both together were used in solid medium and effects of these additional compounds were examined on mass production of hybrid Heterorhabditis bacteriophora HBH strain, which was obtained from hybridization of Turkish isolates. Infective juveniles (IJs) of the strain were targeted as mass production yield criteria. According to the results, all treatments showed statistically better yields compared to control, and lecithin was statistically the best treatment among others. Thus, lecithin could be used as an additional compound in in vitro solid mass production media.

Drivers of entomopathogenic fungi presence in organic and conventional vineyard soils

Entomopathogenic fungi (EPF) are important antagonists of soil-dwelling insect pests adapted to living in agricultural soils. Little is known about EPF in vineyards, where they could be effective against soil-borne pests such as grapevine phylloxera or larvae of the June beetle. However, the high frequency of fungicide applications might reduce the effectiveness of EPF in vineyard soils. We compared effects of organic and conventional management, fungicide applications and soil parameters on natural occurrence of EPF in vineyards. In 15 pairs of organic and conventional vineyards in Germany, soil was sampled and tested for EPF with a baiting method and subsequent genetic identification. A set of plant protection and soil parameters were measured per site. Three taxa could be verified with Metarhizium being the most abundant one. Presence of EPF in general and of Metarhizium spp. was enhanced by a high C:N-ratio. Differences between management systems were minor, with Metarhizium spp. being more abundant in conventional vineyards. We could not detect a negative effect of fungicides on the presence of EPF. Metarhizium spp. was more frequently detected with increasing copper content of vineyard soils. We conclude that EPF are able to persist even in intensively managed vineyard systems. Thus, it would be worthwhile to further explore their potential for the biological control of vineyard pests.

Cropping systems alter the biodiversity of ground- and soil-dwelling herbivorous and predatory arthropods in a desert agroecosystem: Implications for pest biocontrol

In irrigation-maintained desert agroecosystems in northwestern China, cereal crop production occurs mainly as maize (Zea mays L.) monoculture (MM), along with wheat (Triticum aestivum L.) monoculture (WM) and maize/wheat intercropping (MWI). However, our understanding of the role of different cropping systems in regulating the abundance and diversity of ground- and soil-dwelling insect herbivores (pests) and arthropod predators (natural enemies of pests), and thus cascading effects on biological pest control services is still poor. To address this important issue, we measured ground- and soil-dwelling insect pests and associated arthropod natural enemies in fields of MM, WM, and MWI using pitfall traps and hand-sorting in spring and summer at six sites in a desert agroecosystem in northwestern China. Each site contained three cropping systems with cultivation for at least five years. We also calculated the abundance- and richness-based ratios of ground- and soil-dwelling arthropod predators to insect herbivores (P: H ratios) as indices for assessing pest biocontrol services. For ground-dwelling communities, we found that MM harbored more abundant and diverse insect herbivores and insect predators than the other systems, whereas MWI harbored more abundant and diverse non-insect predators and had higher P: H ratios compared with the other systems across seasons. For soil-dwelling communities, we found that MM harbored more abundant and diverse insect herbivores than MWI in spring, whereas WM harbored less abundant and diverse insect herbivores than the other systems in summer. However, MWI harbored more abundant and diverse insect predators than the other systems, whereas WM harbored less abundant and diverse non-insect predators than the other systems in either season. Moreover, MM harbored more abundant and diverse non-insect predators than MWI in summer. The P: H ratios were higher in MWI than in MM and WM in spring, but did not differ across cropping systems in summer. Our results demonstrate that the magnitude and direction of the effects of cropping systems are highly season specific and vary across groups of ground- and soil-dwelling herbivores and predators. Furthermore, intercropping delivers greater pest biocontrol services than monoculture systems. These findings provide key insights towards developing more effective intercropping systems for pest suppression.

The evaluation of entomopathogenic nematode soil food web assemblages across Switzerland reveals major differences among agricultural, grassland and forest ecosystems

Entomopathogenic nematodes (EPNs) occur in natural and agricultural soils and contribute to the control of soil dwelling insect pests. Ecosystems differ in their soil parameters (pH, moisture, texture, etc.) and microhabitat conditions (presence of roots, plant cover, belowground fauna, etc.), which can affect the EPN soil food web assemblage in an unpredictable manner. By comparing soils that represent different ecological scenarios, we can link the natural distribution of the EPN to abiotic and biotic factors that shape the assemblages of soil food web to unravel the factors that determine EPN abundance and activity. We hypothesized that the EPN soil food web assemblages are affected by agricultural management practices and that this should be reflected when compared to natural ecosystems, such as forests and grasslands. By combining traditional and state-of-the-art molecular tools, we targeted 25 soil organisms to explore EPN food web in 40 Swiss georeferenced sites that can be categorized as “agricultural area”, “forest”, and “grassland”. EPNs abundance, richness and diversity did not vary among the different ecosystems. However, EPN activity (capability to kill insects) was higher in grasslands. Similarly, the free-living nematodes (FLNs) that compete with EPN for the cadavers were much more abundant in grassland, while reduced in the forest soils, suggesting contrasting conditions between these two natural areas. Nematophagous fungi (NF) were more diverse and present in agricultural areas, suggesting that the abiotic conditions in the agricultural areas may favor NF presence. Six soil properties and environmental factors shaped the EPN soil food web in Swiss soils (pH, elevation, clay content, soil water content, temperature, and rainfall), which explained 54% of the community variation in multivariate analysis. These observations were consistent with the key abiotic variables described for subtropical and Mediterranean regions. Identifying the links between the abiotic and biotic factors in very distinct areas can be the basis for predicting EPN soil food web assemblages. Such information can be of value for developing strategies to favour EPN resilience in a changing environment and enhance their capacity as biocontrol agents.

Increased neem extract content enhances drying survival of co-encapsulated Saccharomyces cerevisiae and decreases relative release of azadirachtin

ABSTRACTPlant extracts from the neem tree can be applied as a bioinsecticidal compound in ‘attract-and-kill’ co-formulations to control soil-dwelling insect pests. Since insects are attracted to the bioinsecticide, the attract-and-kill approach benefits from a reduced dose of insecticide needed. Here, we demonstrate that a powdery neem seed kernel extract in combination with corn starch significantly enhances the drying survival of co-encapsulated CO2-releasing Saccharomyces cerevisiae. Additionally, an increased content of the neem extract was shown to slow down the relative release of azadirachtin A. Both findings are of high relevance for the development of formulations in the field of biological pest control.