Soil-dwelling Insects Research Articles

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.

The Long horned beetles ( Cerambycidae: Coleoptera) with new records from Pakistan

The longhorn beetles belongs to family Cerambycidae. The beetles are present in almost all ecosystems, except the ocean and Polar Regions. They are most the important biological control agents into agro-ecosystems. The beetles help in the biological control they eat extensive assortments of tree dwelling, soil dwelling insects and also eat caterpillars, maggots, aphids, bug, ants, wasp. Long horned beetles were gathered from different sites (agricultural fields and their surrounding vegetation) of district Naushahro Feroze with insect net (7.79 cm in diameter and 49.9 cm in length) and hand picking. A of 234 specimens were captured from October 2018 to July 2019. The material was identified into 07 species out of 06 genera. Of which Batocera rubus (Linnaeus, 1758), New Record from Sindh, Batocera rufomaculata (Charles De Geer, 1775), New Record from Sindh, Apriona cinerea (Chevrolat, 1852), New Record from Sindh, Archopalus exoticus (Sharp, 1905), New Record from Pakistan Macrotoma crenata (Fabricius, 1801), New Record from Pakistan, Prionus corpulantus (Bates, 1878) New Record from Sindh, Dorysthenes hugelii (Redtenbacher, 1848), New Record from Pakistan. The highest ratio of specimens were recorded from Mehrabpur and lowest ratio of specimens were recorded from Moro.

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.

Characterization and Pathogenicity Test of Entomopathogenic Nematode Steinernema Species-Kalro

Entomopathogenic nematodes (EPNs) are worldwide soil-dwelling insect parasitic nematodes. They are potential pest bio-control agents a key component of Integrated Pest Management (IPM) programs. This study aimed to characterize and evaluate the pathogenicity of an EPN isolate from Kenya. The nematode was isolated from soils using insect bait technique and both morphological and molecular identification was performed. Efficacy of the isolate was evaluated against Tomato leafminer larvae (Tuta absoluta Meyrick.) using dose-based treatments of 0-control, 100, 150, 200, and 250 infective juveniles (IJs/ml). Morphological analysis revealed body length (L) of 835(659-987) µm and 1781 (1297-2097) µm from fresh IJs and males respectively. Males lacked a mucron. The isolate was characterized by the partial sequence length of 877 bp of the ITS region. Blastn results indicated the EPN isolate had a similarity match of 81-92% with Afro-tropical Steinernema species. It matched with Steinernema sp. (AY230186.1) from Kenya at 92% and Sri Lanka (AY230184.1). Phylogenetic analysis placed the isolate together with Steinernema sp. (AY230186.1) and (AY230184.1) with a bootstrap value of 100%. Maximum mean larval mortality (80%; 96%) was achieved 24 and 48 h post-treatment at concentration 150 IJs/ml. All nematode concentrations achieved over 50% mean mortality after 24 h period. There was a significant difference (P = 0.001) between doses 150 and 200 IJs/ml. From the study, it was concluded that the nematode isolate was Steinernema sp now referred to as Steinernema sp. Kalro (Genebank Accession MW151701). The EPN has the potential for development as a biological control agent against T. absoluta.

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.

Effects of soil application of two different fipronil formulations on some soil-dwelling non-target arthropods

Soil arthropods, including soil insects and mites, play a significant role in the recycling of fertility material and maintenance of soil structure. This study was performed to determine the non-target effects of two different formulations of fipronil on four groups of soil-dwelling insects (collembola, earwig, staphylinids and ants) and one group of mites. The pitfall traps were installed to estimate the arthropod population. The population per trap was evaluated after 3, 6, 9 12, 15, 18 and 21 days after insecticides’ application. The population of soil-dwelling arthropods was significantly reduced in the case of fipronil 5% SC (soluble concentration) treated plots after 3 and 6 days of application. However, the fipronil 0.3 GR (granule) was more toxic at 9th and 12th day of application. The toxicity of fipronil was decreased with the passage of time but fipronil 0.3 GR remained toxic until 18 days in some cases. Hence, both formulations of fipronil reduced the population of non-target soil arthropods, but fipronil 5% SC was more toxic than fipronil 0.3 GR when compared with the untreated check (control plot). According to these results, the application of fipronil should be reduced and find an alternative way instead of this pesticide.

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.

Xenorhabdus bovienii strain jolietti uses a type 6 secretion system to kill closely related Xenorhabdus strains

Xenorhabdus bovienii strain jolietti (XBJ) is a Gram-negative bacterium that interacts with several organisms as a part of its life cycle. It is a beneficial symbiont of nematodes, a potent pathogen of a wide range of soil-dwelling insects and also has the ability to kill soil- and insect-associated microbes. Entomopathogenic Steinernema nematodes vector XBJ into insects, releasing the bacteria into the insect body cavity. There, XBJ produce a variety of insecticidal toxins and antimicrobials. XBJ's genome also encodes two separate Type Six Secretion Systems (T6SSs), structures that allow bacteria to inject specific proteins directly into other cells, but their roles in the XBJ life cycle are mostly unknown. To probe the function of these T6SSs, we generated mutant strains lacking the key structural protein Hcp from each T6SS and assessed phenotypes related to different parts of XBJ's life cycle. Here we demonstrate that one of the T6SSs is more highly expressed in in vitro growth conditions and has antibacterial activity against other Xenorhabdus strains, and that the two T6SSs have a redundant role in biofilm formation.

Three-dimensional cellular aggregates formed by Beauveria pseudobassiana in liquid culture with potential for use as a biocontrol agent of the African black beetle (Heteronychus arator)

ABSTRACT Beauveria pseudobassiana formed three-dimensional aggregates of cells (CAs) in liquid culture. CAs were formed mainly by blastospores and conidia, distinct from microsclerotia formed through adhesion of hyphae. The formation, germination and sporulation of CAs were studied, as well as the pathogenicity of conidia produced from them against adults of black beetle. After 4 days of culture, CAs were formed, becoming compact and melanised after 10 days of incubation. Electron microscopy showed three-dimensional CAs averaging 431.65 µm in length with irregular shapes and rough surfaces, where cells were trapped within an extracellular matrix. CAs germinated after 2 days of incubation on agar-plates producing hyphae and forming phialides and conidia after 4 days. Produced conidia caused 45% mortality of black beetle adults. CAs germination and sporulation on soil were directly correlated with soil moisture, reaching 80% and 100% germination on the surface of soil with 17% and 30% moisture, respectively. CAs maintained 100% germination after 2 years of storage under refrigeration. These CAs could have a similar function as microsclerotia in nature, acting as resistant structures able to protect internal cells and their ability to sporulate producing infective conidia, suggesting their potential to be used as bioinsecticides to control soil-dwelling insects.

Bacterial community profile after the lethal infection of Steinernema-Xenorhabdus pairs into soil-reared Tenebrio molitor larvae.

The host microbiota may have an impact on pathogens. This is often studied in laboratory-reared hosts but rarely in individuals whose microbiota looks like that of wild animals. In this study, we modified the gut microbiota of the insect Tenebrio molitor by rearing larvae in soil sampled from the field. We showed by high throughput sequencing methods that this treatment modifies the gut microbiota so that it is more diversified than that of laboratory-reared insects, and closely resembled the one of soil-dwelling insects. To describe what the entomopathogenic bacterial symbiont Xenorhabdus (Enterobacteriaceae), vectored by the soil-dwelling nematode Steinernema, might experience in natural conditions, we studied the infestation of the soil-reared T. molitor larvae with three Steinernema-Xenorhabdus pairs. We performed the infestation at 18°C, which delays the emergence of new infective juveniles (IJs), the soil-dwelling nematode forms, but which is a temperature compatible with natural infestation. We analyzed by high throughput sequencing methods the composition of the bacterial community within the insect cadavers before the first emergences of IJs. These bacterial communities were generally characterized by one or two non-symbiont taxa. Even for highly lethal Steinernema-Xenorhabdus pairs, the symbiont does not dominate the bacterial community within the insect cadaver.

Encapsulated Entomopathogenic Nematodes Can Protect Maize Plants from Diabrotica balteata Larvae.

To face the environmental problems caused by chemical pesticides, more ecologically friendly alternative pest control strategies are needed. Entomopathogenic nematodes (EPN) have great potential to control soil-dwelling insects that cause critical damage to the roots of cultivated plants. EPN are normally suspended in water and then sprayed on plants or onto the soil, but the inconsistent efficiency of this application method has led to the development of new formulations. Among them is the use of alginate capsules or beads that encapsulate the EPN in favorable conditions for later application. In this study, we evaluated whether alginate beads containing EPN are able to kill larvae of the banded cumber beetle Diabrotica balteata LeConte and thereby protect maize plants from damage by these generalist rootworms. EPN formulated in beads were as effective as sprayed EPN at killing D. balteata. They were found to protect maize plants from D. balteata damage, but only if applied in time. The treatment failed when rootworm attack started a week before the EPN beads were applied. Hence, the well-timed application of EPN-containing alginate beads may be an effective way to control root herbivores.

Understanding scion-rootstock interactions at the graft interface of grapevine

In viticulture, grafting is used to facilitate grapevine cultivation in soils infected with phylloxera, a soil-dwelling insect pest introduced to Europe from America at the end of the 19th century. Successful grafting of plants is a complex biochemical and structural process that begins with an initial wound response, followed by callus formation and the establishment of a functional vascular system between the two grafting partners. Despite the importance of the scion-rootstock interface in viticulture, we know little of the processes involved in forming a successful graft union. Developments at the scion-rootstock interface of grapevine have been studied using a variety of techniques. Morphological developments have been studied using microscopy techniques and X-ray computed tomography, and xylem connectivity has been assessed by using a high- and low-pressure flow meter. Microarrays have been used to identify genes that are differentially expressed between the wood and graft interface tissues of homo-grafts (the same genotype grafted together) and at the graft interface between different scion-rootstock combinations (hetero-grafts). Primary and secondary metabolite profiling has also been done. An overview of the interdisciplinary approaches currently being used to piece together the puzzle of graft union formation in an important woody, perennial crop will be presented.

Elevated atmospheric carbon dioxide concentrations alter root morphology and reduce the effectiveness of entomopathogenic nematodes

The effects of increasing atmospheric carbon dioxide (CO2) concentrations on beneficial soil fauna, such as entomopathogenic nematodes (EPNs), are poorly understood. We hence aimed to characterize how elevated CO2 (eCO2) affects maize plant (Zea mays) growth, root morphology and the effectiveness of the EPN Heterorhabditis bacteriophora. We grew plants under ambient CO2 (aCO2; 400 μmol mol-1) and eCO2 (640 μmol mol-1) and quantified shoot growth and six root traits. We simultaneously quantified the effectiveness of EPNs (mortality of insect hosts (Galleria mellonella) and EPN density within hosts) when foraging in planted and plant-free environments. Structural equation modeling (SEM) was used to model direct and indirect relationships between atmospheric CO2, root morphology and EPN effectiveness. Root systems of plants grown under eCO2 grew faster, longer, denser, and larger than plants grown under aCO2. This in turn reduced EPN effectiveness as, despite no significant difference between aCO2 and eCO2 in host mortality, significantly more nematodes were recovered from hosts in the vicinity of plants grown in aCO2 environment. The SEM model revealed that this impact was indirect and mediated by the increased root morphological traits. We provide the first example of how changes in atmospheric CO2 indirectly reduce the effectiveness of an EPN used globally for crop protection. Other factors (e.g. plant volatile emissions) may moderate or exacerbate these patterns but our findings suggest that modifications in root traits at eCO2 negatively impact EPN effectiveness and therefore soil-dwelling insect pest management.

Ecological characterization of Heterorhabditis sonorensis (Caborca strain) (Nematoda: Heterorhabditidae), an entomopathogenic nematode from the Sonoran Desert

Heterorhabditis nematodes are parasites of a wide range of soil-dwelling insect species. Although these nematodes have been exploited as biological control agents since the last half of the 20th century, much research remains to be done to understand how these organisms function in agricultural and other ecosystems. In this study, we present some ecological traits of Heterorhabditis sonorensis, a natural parasite of the cicada Diceroprocta ornea, from the Sonoran Desert. Specifically, we evaluated its infectivity across a diverse panel of insect groups and assessed its fitness (infectivity and reproduction) considering different temperatures, and soil moisture levels. Three other Heterorhabditis species served as points of comparison for temperature and soil moisture assays. Host range experiments indicate that H. sonorensis, although isolated from seasonal cicada nymphs, is more virulent and reproductively fit in the lepidopteran hosts tested. This nematode has an optimum temperature range at 25–30 °C but can also successfully reproduce at temperatures ranging from 15 to 35 °C. Additionally, this nematode is adapted to a variety of soil moisture conditions with successful infections across the tested moisture range (3%–20%). Finally, we demonstrate that H. sonorensis infective juveniles have a high survival rate (over 80%) at various storage temperatures (10–25 °C) after 24 weeks of storage and remain infective as revealed by the post-storage infection assays.

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.

Uticaj različitih tretmana semena na oštećenja od žičara (Elateridae) i parametre prinosa suncokreta (Helianthus annuus L.)

Sunflower seed treatments are inevitable measure that ensures protection from soildwelling insects and pathogens at the first stages of plant development. Due to the ban of neonicotinoid based insecticides for the sunflower seed treatments, new registered preparations are put to test. The aim of this work was to assess the efficacy of currently registered insecticides against the wireworms (observed in field emergence and percent of damaged plants) and their effect on yield traits (yield, oil content and 1, 000-seed weight) of the sunflower hybrids (Sumo 2 OR, Oliva and Novak) in comparison to previously used neonicotinoids. Seeds were treated with different pesticidal combinations: metalaxyl-m, metalaxyl-m + bifenthrine, metalaxylm + thiacloprid, metalaxyl-m + thiametoxam, and metalaxyl-m + imidacloprid. Twoway ANOVA and Duncan’s multiple range tests were performed. Field emergence was not influenced by the treatment. Sumo 2 OR and Oliva emergence did not differ significantly among the treatments (78.3-88.3%; 83.0-91.3%, respectively), but for Novak it was significantly lower (79.3%) when treated with metalaxyl-m. The lowest percent of damaged plants was in the treatment with metalaxyl-m + thiametoxam (1.1-2.4%). However, it did not differ significantly among other treatments (2.4-3.9%), regardless on the hybrid. Novak had the highest average yield (3,938.1 kg*ha-1), followed by Sumo 2 OR (3,566.1 kg*ha-1), and Oliva (3,199.8 kg*ha-1), regardless on the applied seed treatments. The highest 1,000-seed weight was measured for Oliva. Given indicates that currently registered insecticides for the seed treatment of sunflower, such as Sonido and Semafor, can be adequate substitute to the banned neonicotinoids like Cruiser and Gaucho.

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.

Evaluation of local isolates of entomopathogenic nematodes for the management of black cutworm, Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae)

The black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) is considered to be one of the serious polyphagous pests that spend a large part of its life in the soil environment, where many microorganisms live including entomopathogenic nematodes (EPNs) (Rhabditida: Steinernematidae and Heterorhabditidae). EPNs have been long used for suppressing the soil-dwelling insects like cutworms and are successful biological control agent against A. ipsilon larvae. In the present study, the efficacy of local EPNs isolates against the fourth larval instar of A. ipsilon was evaluated at different concentrations (10, 25, 50, 100 IJs/larva/Petri dish and 25, 50, 100 IJs/cm2 soil) in two different experiment environments including filter papers in Petri dishes and soil in plastic containers under laboratory conditions at 25 ± 1 °C. Larval mortalities of A. ipsilon were recorded first, second, third, and fourth day post inoculation where the mortality rates increased by increasing the concentrations. The maximum mortality rate (100%) was reached within 2 days after inoculation, inoculating the Heterorhabditis bacteriophora FLH-4-H and H. indica 216-H isolates at concentrations of 50 and 100 IJs/cm2, in the plastic container experiment. The highest mortality rate (90%) was obtained by Steinernema carpocapsae E76-S isolate at a concentration of 100 IJs/larva/Petri on the fourth day after inoculation, in the Petri dish experiment. The lethal concentration values (LC50 and LC90) of the A. ipsilon larval population were 52 IJs and 129 IJs, respectively, for S. feltiae E76-S isolate in the Petri dish tests. In the plastic container experiment, the lowest LC50 and LC90 values found to be 17 IJs and 23 IJs, respectively, for H. bacteriophora FLH-4-H isolate. The results showed that all indigenous EPN isolates had good potentials in the management of A. ipsilon.