Strains Of Entomopathogenic Nematodes Research Articles

Long-term suppression of turfgrass insect pests with native persistent entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) can control several important turfgrass insect pests including white grubs, weevils, cutworms, and sod webworms. But most of the research has focused on inundative releases in a biopesticide strategy using EPN strains that may have lost some of their ability to persist effectively over years of lab maintenance and / or selection for virulence and efficient mass-production. Our study examined the potential of fresh field isolate mixes of endemic EPNs to provide multi-year suppression of turfgrass insect pests. In early June 2020, we applied isolate mixes from golf courses of the EPNs Steinernema carpocapsae, Heterorhabditis bacteriophora, and their combination to plots straddling fairway and rough on two golf courses in central New Jersey, USA. Populations of EPNs and insect pests were sampled on the fairway and rough side of the plots from just before EPN application until October 2022. EPN populations increased initially in plots treated with the respective species. Steinernema carpocapsae densities stayed high for most of the experiment. Heterorhabditis bacteriophora densities decreased after 6 months and stabilized at lower levels. Several insect pests were reduced across the entire experimental period. In the fairway, the combination treatment reduced annual bluegrass weevil larvae (59 % reduction) and adults (74 %); S. carpocapsae reduced only adults (42 %). White grubs were reduced by H. bacteriophora (67 %) and the combination (63 %). Black turfgrass ataenius adults were reduced in all EPN treatments (43–62 %) in rough and fairway. Sod webworm larvae were reduced by S. carpocapsae in the fairway (75 %) and the rough (100 %) and by H. bacteriophora in the rough (75 %). Cutworm larvae were reduced in the fairway by S. carpocapsae (88 %) and the combination (75 %). Overall, our observations suggest that inoculative applications of fresh field isolate mixes of endemic EPNs may be a feasible approach to long-term suppression of insect pests in turfgrass but may require periodic reapplications.

The Efficacy of Entomopathogenic Nematodes Plus an Adjuvant against Helicoverpa zea and Chrysodeixis includens in Aboveground Applications.

In the southern United States, corn earworm, Helicoverpa zea (Boddie), and soybean looper, Chrysodeixis includens (Walker) are economically important crop pests. Although Bt crops initially provided effective control of target pests such as H. zea, many insect pests have developed resistance to these Bt crops. Alternative approaches are needed, including biological control agents such as entomopathogenic nematodes (EPNs). However, the effectiveness of EPNs for aboveground applications can be limited due to issues such as desiccation and ultraviolet radiation. Effective adjuvants are needed to overcome these problems. Ten strains of EPNs were tested for virulence against eggs, first to fourth instars, fifth instars, and pupae of H. zea and C. includens in the laboratory. These 10 EPN strains were Heterorhabditis bacteriophora (HP88 and VS strains), H. floridensis (K22 strain), Hgkesha (Kesha strain), Steinernema carpocapsae (All and Cxrd strains), S. feltiae (SN strain), S. rarum (17c+e strain), and S. riobrave (355 and 7-12 strains). EPNs could infect eggs of H. zea or C. includens in the laboratory, but the infection was low. The mortality caused by 10 EPN strains in seven days was significantly higher for the first to fourth instars of H. zea compared to the control, as was the fifth instars of H. zea. Similarly, for the first to fourth and fifth instars of C. includens, the mortality was significantly higher compared to the controls, respectively. However, only S. riobrave (355) had significantly higher mortality than the control for the pupae of H. zea. For the pupae of C. includens, except for H. bacteriophora (HP88), S. rarum (17c+e), and H. floridensis (K22), the mortality of the other seven strains was significantly higher than the control. Subsequently, S. carpocapsae (All) and S. riobrave (7-12) were chosen for efficacy testing in the field with an adjuvant 0.066% Southern Ag Surfactant (SAg Surfactant). In field experiments, the SAg Surfactant treatment significantly increased the mortality and EPN infection for S. carpocapsae (All) on first instars of H. zea in corn plant whorls. On soybean plants, with the SAg Surfactant, S. carpocapsae (All) was more effective than S. riobrave (7-12) on fifth instars of C. includens. This study indicates that EPNs can control H. zea and C. includens, and SAg Surfactant can enhance EPN efficacy.

Standardization of Formulation and Application Approaches for Field Implementation of EPNs

Entomopathogenic nematodes (EPNs) live parasitically inside the infected insect host, and so they are termed as endoparasitic. They infect different types of insect living in the soil like the larval forms of moths, butterflies and beetles as well as adult forms of beetles, grasshoppers and crickets. The present experiment was conducted under both laboratory and field conditions at CCS Haryana Agriculture University, Hisar. Two most virulent strains of EPNs, Metarhabditis amsactae strain HAR-St-II and HAR-Ht-III were taken and their formulations were standardized using six different media i.e. cadaver based formulation, water, alginate gel, foam chips, clay chips and water dispersible granules. Among these formulations, cadaver based formulation was found to be best. Maximum numbers of active IJs after 90 days were obtained from this formulation were 3370 and 2728 /Petri plate in strain HAR-St-II and HAR- Ht-III of M. amsactae, respectively. Further this, experiment was conducted at field level for EPNs suspension was standardized using different size of nozzle opening i.e. 25 µm, 50 µm, 75 µm and 100 µm on knapsack sprayer. Spodoptera litura was selected as a test insect in okra crop for foliar application of EPNs and results revealed that 100 µm nozzle opening size gave maximum larval mortality of S. litura. Per cent mortality of S. litura was increased with increase in size of nozzle and period of observation

Movers and shakers: Do nematodes that move more invade more?

Entomopathogenic nematodes (EPNs) are roundworms that parasitize insects with the aid of symbiotic bacteria. These nematodes have been used both as model organisms and for biological control of pests. The specialized third stage of an EPN, known as an infective juvenile (IJ) must forage to find a host with strategies varying from species to species (cruising, ambushing, and intermediate). Some IJs move more than others to find a host, despite an increased risk of predation and desiccation. This hints at potential underlying benefits (e.g., increased invasion) for EPNs that move more. We assessed whether EPNs that moved farther down a soil column also exhibit higher levels of invasion when compared to nematodes that remained at or near their point of origin. We found that movers in the cruisier and intermediate species: Steinernema riobrave, Heterorhabditis bacteriophora, and H. indica had higher invasion rates compared to their counterparts that did not move. S. carpocapsae, an ambusher, did not exhibit invasion differences between EPNs that moved versus those that did not. For the three cruiser/intermediate EPNs we tested, our results support our hypothesis that EPNs that tend to move more enjoy related benefits such as increased invasion potential. Further studies are required to explore other parameters that may interact with movement. The results of this study can potentially be used to develop EPN strains that move more and invade more, and thus can potentially be more effective biological control agents.

Biocontrol potential of entomopathogenic nematode, Heterorhabditis indica against pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

BackgroundThe emergence of pink bollworm (PBW), Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), in cotton due to Bt resistance and concealed feeding habit has created a need for alternative, eco-friendly, and cost-effective control methods. This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes (EPNs), Heterorhabditis indica, namely CICR-HI-CL and CICR-HI-MN, against PBW larvae and pupae under in-vitro conditions.ResultsThe larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd, 3rd, and 4th instar larvae, with median lethal dose (LD50) values of 5.45, 4.45, and 4.60 infective juveniles (IJs) per larva, respectively. In case of pupal bioassay, both EPN strains demonstrated greater virulence when applied directly (LD50 values: 29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN, respectively) compared to soil application (147.84 and 272.38 IJs per pupa). Both EPN strains successfully penetrated and reproduced on 4th instar larvae, resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.ConclusionThe present study has generated useful information on the virulence and reproductive potential of two strains of EPN H. indica (CICR-HI-CL and CICR-HI-MN) against PBW, a dreaded pest of cotton. Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply, sustain and perpetuate on larval and pupal stages of PBW. The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate. The soil-dwelling life stages viz., last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H. indica for sustainable management of PBW in the cotton ecosystem. However, before taking these EPN strains to field for managing PBW, detailed studies investigating their biocontrol potential against PBW under field conditions are needed.

In Vivo Production, Development and Storage of Oscheius myriophila (Nematoda: Rhabditida) in Galleria mellonella (Lepidoptera: Pyralidae).

Entomopathogenic nematodes have been used in biological control for some time and are an alternative for the control of insect pests, but during their implementation, situations have arisen that can be improved. These vary with each species and include their production and storage. Oscheius myriophila, an entomopathogenic nematode (EPN), was monitored for its performance when produced in vivo, as well as its development using Galleria mellonella larvae, using the MC5-2014 strain isolated from soil samples in the municipality of Tepalcingo, Morelos, México. For a study with native strains of EPNs, a wide range of tests must be conducted because the required conditions can be very specific. In vivo production was quantified at initial infective juvenile (IJ) inocula of 50, 100 and 500, and we obtained the same production for the three inocula. The life cycle of the EPNs lasted 12 days, and two generations were observed in which adults were found at days 5 and 9. Both evaluations were performed at a temperature of 27 °C in G. mellonella larvae. In addition, the temperatures of 8, 12, 20 and 24 °C were evaluated for their storage, and we observed that the EPNs can be kept for at least 6 months, maintaining a survival rate of 58.67% and a good infective capacity at a temperature of 12 °C, remaining above 60%.

In vitro liquid culture production and post-production pathogenicity of the hybrid Heterorhabditis bacteriophora HBH strain

Entomopathogenic nematodes (EPNs) are biological control agents that can be used as alternatives to chemical pesticides against insect pests. Liquid culture is the most suitable method for large-scale production of EPNs. However, to achieve commercial success, the optimization of production parameters is crucial. This study aimed to identify the optimal temperature, pH and dissolved carbon dioxide concentration for the liquid culture production of Heterorhabditis bacteriophora hybrid HBH strain. Temperature and pH experiments were conducted in Erlenmeyer flasks, while carbon dioxide experiments were conducted using a 5 L bench-top fermenter. The results revealed that the best yield was achieved at a temperature of 26 °C, a pH of 9, and a dissolved carbon dioxide concentration of 8–9%. The highest yield was observed between the 14th to 16th days in almost all batches. Although no significant difference was found in the pathogenicity of the populations, certain populations obtained from carbon dioxide trials exhibited greater efficacy at lower doses than in vivo populations. The liquid production of the HBH hybrid strain is a critical step towards commercial production. Further goals include the optimization of additional parameters for large-scale production. The findings of this study are expected to have practical implications for the industrialization of native hybrid EPN strains.

Pathogenicity of native Strains of Entomopathogenic Nematodes against Aphids and Pseudostem Weevil

The pathogenicity of three native strains of entomopathogenic nematodes isolated from different locations of Kerala were evaluated against aphids, Aphis craccivora Koch and 4th instar grubs of banana pseudostem weevil, Odoiporous longicollis Olivier under laboratory condition. Based on the morphological characters and morphometric measurements, they were identified as Steinernema sp., Metarhabditis sp. and Rhabditis sp. Metarhabditis sp. @ 100 IJs (infective juveniles) recorded 100% mortality of aphids at 48 HAT (hours after treatment) and it was statistically on par with dimethoate 30EC. Metarhabditis sp.@ 100 and 200 IJs/ insect showed 47.49 and 62.66% mortality of pseudostem weevil grubs at 72 HAT. Molecular characterization of the most potent isolate effective against both the pests was done and it was identified as Metarhabditis rainai.

Effectiveness of botanical insecticides on larval stage of red palm weevil Rhynchophorous ferrugineus and survival of entomopathogenic nematodes

Botanical oils are considered ecofriendly compounds with insecticidal characteristics. In this study, the effects of basil (Ocimum basilicum), camphor (Cinnamomum camphora), cinnamon (Cinnamomum verum), lemon (Citrus limon), clove (Syzygium aromaticum), ginger (Zingiber officinale), black pepper (Piper nigrum), and orange (Citrus sinensis var balady) oil extracts on the survival of four entomopathogenic nematode strains belonging to the Steinernema and Heterorhabditis genera, as well as their impacts on Rhynchophorus ferrugineus egg hatching and larvae, were assessed. The results for the camphor, lemon, black pepper, and orange oils were promising as 50 μL/mL of each resulted in 0%, 0%, 16%, and 0% hatchability for the R. ferrugineus eggs, respectively. Furthermore, the mortality of R. ferrugineus larvae was up to 95% with the similar concentrations and an exposure time of 48 h, for the other investigated oils. Various morphohistopathological alterations were found in the cuticle; outer cuticle folds swelling or shrinkage and subcuticular muscle degeneration, as well as midgut; fat globules in the epithelial lining with marked degeneration and/or necrosis, of the R. ferrugineus larvae when compared with those of controls replicates. Mortality percentage of infective juveniles (IJs) of Steinernema carpocapsae (S2) was significantly lower than Heterorhabditis marelatus (D1), Steinernema riobravae (Sr) and Steinernema carpocapsae (All) when using camphor oil compared to the other oils (50%). From the obtained observations on oils lethal effects, the target of developing integral biocontrol product formulated from combinations of essential oils and nematode with insecticidal properties against R. ferrugineus (not nematode survival) is possible; a sustainable and ecofriendly product for pest management.

Isolation of Native Strains of Entomopathogenic Nematodes against Fall armyworm, Spodoptera frugiperda (Smith.) in Maize

Entomopathogenic Nematodes (EPNs) found in a variety of soil types, geographical regions, and hosts, which belong to the genera Steinernematidae and Heterorhabditidae, have the potential to act as biocontrol agents. In comparison to chemical and microbial pesticides, they performed better. A total of 87 soil samples were taken from regions where maize was grown in Tuticorin district, Tamil Nadu, India and they were examined for the presence of EPN in 2022–2023. By using the Corcyra baiting approach, a total of 9 samples (10.33%) showed EPN-positive sites. A total of 8 Steinernema sp. (13.33%) and 1 Heterorhabditis sp. (5.00%) were isolated from that population. EPN is identified at a generic level using the cadaver’s colour. Heterorhabditis displays brick red, while Steinernema exhibits creamy white. At a dose of 100–600 IJs/larva for the third and fifth instar, the isolated efficient native EPN strain (Kayathar strain) demonstrated mortality of 95.00–100.00% and 94.50–99.80%. According to the study, EPN showed considerable potent against Spodoptera frugiperda. So, EPNs may be used as a promising bio-control agent to battle pests of the maize crop.

Compatibility of Egyptian strains of entomopathogenic nematodes (Nematoda: Rhabditida) with insecticides and their activity against Spodoptera frugiperda (Lepidoptera: Noctuidae) under laboratory conditions.

Compatibility of Egyptian strains of entomopathogenic nematodes (Nematoda: Rhabditida) with insecticides and their activity against Spodoptera frugiperda (Lepidoptera: Noctuidae) under laboratory conditions.

Use of Entomopathogenic Nematodes for the Management of Banana Rhizome Weevil (Cosmopolites sordidus): A Review

Banana is an important fruit crop which is grown in tropical and subtropical parts of the world. Banana production is inhibited by various insect pests. Though chemical insecticides are recommended for control of these pests, use of biocontrol agents are alternative method .One of the biocontrol agents is the entomopathogenic nematodes (EPNs). This review finds the work of some of the successful EPN species or strains from different geographical locations that may affect practical bio control of banana rhizome weevil, a major pest of banana. Emphasis is made on roles of EPNs in reducing banana rhizome weevil (Cosmopolites sordidus) and directions of future research in biocontrol programme are presented.

Popillia japonica - Italian outbreak management.

Popillia japonica, a priority pest for the EU, was first detected in Northern Italy in 2014. Since its discovery, the outbreak extended over an area of more than 16,000 square kilometers in Northern Italy and Southern Switzerland. In this review, we summarize the state-of-the-art of research conducted in Italy on both the spreading capacity and control measures of P. japonica. Chemical, physical, and biological control measures deployed since its detection are presented, by highlighting their strengths and weaknesses. An in-depth study of the ecosystems invaded by P. japonica disclosed the presence and pathogenicity of natural strains of entomopathogenic fungi and nematodes, some of which have shown to be particularly aggressive towards the larvae of this pest under laboratory conditions. The Plant Health authorities of the Lombardy and Piedmont regions, with the support of several research institutions, played a crucial role in the initial eradication attempt and subsequently in containing the spread of P. japonica. Control measures were performed in the infested area to suppress adult populations of P. japonica by installing several traps (e.g., for mass trapping, for auto-dissemination of the fungus Metarhizium anisopliae, and "attract & kill"). For larval control, the infested fields were treated with commercial strains of the entomopathogenic fungus M. anisopliae and nematode Heterorhabditis bacteriophora. Future studies will aim at integrating phenological and spread models developed with the most effective control measures, within an ecologically sustainable approach.

Evaluation of Indigenous Strains of Entomopathogenic Nematodes, in Combination with Low-Toxicity Insecticides for Control of Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae)

A study was conducted during November, 2021 to evaluate the efficacy of local strains of Steinernema feltiae and Heterorhabditis bacteriophora in combination with low-toxicity insecticides at low and high dosages to control fifth-instar larvae in under laboratory condition. The experimental location in Department of Entomology, Nematology Laboratory, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh, India. The use of S. feltiae+Spinosad or chlorantraniliprole caused larvae mortality of over 90% at 96 h and H. bacteriophora+Spinosad or Chlorantraniliprole mortality caused of over 95% mortality at 96 h after treatment at the high dose and may be considered as a least toxic strategy to control fall armyworm. Our results showed that these strains of H. bacteriophora have high pathogenicity against S. frugiperda and have potential for biological control in integrated approaches causing even combination with low-toxicity insecticides at low and high dosages may be considered 90% mortality fifth instar larval of S. frugiperda at 96 h at the high dose as a least toxic strategy to control fall armyworm. The use of S. feltiae+Spinosad or chlorantraniliprole and H. bacteriophora+Spinosad or chlorantraniliprole caused larvae mortality of over 90% high dose and should be included as a least toxic strategy to control fall armyworm. Native strains of entomopathogenic nematodes are active against S. frugiperda shows potential alternative to the severe use of chemical insecticides to control fall armyworm population in corn plantations.

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.

Manifestation and dispersal of entomopathogenic nematodes in orchard ecosystem with regards to soil characters in three different zones of Chhattisgarh state

Entomopathogenic nematodes (EPNs) are round worms from the genera Steinernematid and Heterorhabditid. They are ubiquitous in nature. Survey results of the present study show that 7 samples out of 800 collected samples (0.87%), were positive for EPN which were obtained from silty loam and loamy sand soil. This is an extensive first of its kind study on EPN survey throughout the state of Chhattisgarh. The EPN were recovered from 5 of the 24 surveyed districts namely Baloda Bazar (Ber crop), Mahasamund (Mango crop), Raipur (Sapota crop, Papaya and guava), Bijapur (Mango crop), Sukma (Mango crop). The organic matter estimate from EPN recovered soils were found to be in the range of 0.56- 1.06 % with pH of slight acidic to neutral (5.6-7.1). Water holding capacity of EPNs isolated soil was 32.05 - 38.87 % and bulk density was 0.96 – 1.27 g/cm3 with moisture percentage of 4.26- 24 %. The present study shows that nematodes can be found in low moisture soil as well as high moisture soils. The results of molecular identification reveals that isolated EPN samples were identified as Heterorhabditis indica. EPNs are being investigated primarily for biocontrol purposes. There are many exotic EPN which had conflicting results in many field testing situations, most likely due to their low adaption to local agro-climatic conditions. Henceforth our quest was to look for an indigenous variety of EPN which can be used as a novel bio pesticide, our work mainly focuses on identification of local EPN strains from Chhattisgarh state which can be further used in Integrated Pest Management programme.

Evaluation of Indigenous Strains of Entomopathogenic Nematodes, in Combination with Low-Toxicity Insecticides at Low and High Dosages South American Tomato Pinworm, Tuta absoluta (Meyrick) (Lepidoptera, Gelechiidae)

The laboratories experiments were conducted during September, 2021 to test the pathogenicity of two EPNs species S. feltiae and H. bacteriophora at different (IJs cm-2) concentrations against Tuta absoluta (Meyrick)(Lepidoptera, Gelechiidae). The experimental location in Department of Entomology, Nematology Laboratory, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh, India. The native isolate was obtained from soil samples, collected from survey was carried out in Mid-hills of the North Himalayas, India, to investigate the diversity and frequency of entomopathogenic nematodes (EPNs). Our objective was to evaluate the efficacy of S. feltiae (HR1) and H. bacteriophora (HR2) in combination with low-toxicity insecticides at low and high dosages to control final-instar larvae in bioassays. The use of S. feltiae+Spinosad or chlorantraniliprole caused larvae mortality of over 100% at 96 h and second bioagent H. bacteriophora+Spinosad and chlorantraniliprole mortality of over 97.50% at 96 h at the high dose and should be included as a least toxic strategy to control T. absoluta. Our results showed that T. absoluta were suitable hosts for local indigenous strains performed good potential for biological control against invasive species. In combination with low-toxicity insecticides at low and high dosages to control final-instar larvae mortality of over 100% at 96 h at the high dose and should be included as a least toxic strategy to control tomato pinworm.

Direct antagonistic effect of entomopathogenic nematodes and their symbiotic bacteria on root-knot nematodes migration toward tomato roots

AimsNegative interactions in the rhizosphere between entomopathogenic nematodes (EPNs) and plant-parasitic nematodes, such as root-knot nematodes (RKNs), have been documented over the past two decades but the mechanisms and dynamics of such interactions remain largely elusive.MethodsHere, we evaluated the effect of the inoculation position of two EPN species, Steinernema feltiae and Heterorhabditis bacteriophora, as well as different facets of the EPN-bacterial symbiont complex on the migration of RKNs toward tomato roots, both in sand and in Pluronic gel conditions.ResultsWhen EPNs were placed between the position of the RKNs and the roots, the movement of RKNs toward the roots was inhibited. We observed this same pattern both in sand and in Pluronic F-127 (PF-127) gel for two species of EPNs. We also observed that different components of the EPNs/bacterial symbiont complex (bacteria separate from the nematodes vs. the nematode-bacterium complex), and particularly the cell-free supernatant produced by the bacterial culture, displayed inhibitory effects on RKNs.ConclusionTherefore, the EPNs/bacterial complex, by slowing down the movement of RKNs toward the host plant roots, could partially contribute to RKN control. By screening for the most repulsive strains of EPNs that are also effective against insect pests, the combined target approach should alleviate EPNs application costs in integrated pest management practices.

Efficacy of native strains of entomopathogenic nematode, Heterorhabditis indica against the fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) from India

Abstract Background The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a notorious polyphagous pest that has recently invaded India in 2018. Within a short period, this pest has spread throughout the country, causing a significant damage to maize. In order to manage this menace, farmers rely on chemical insecticides, but due to concealed feeding nature of this pest insecticides remain ineffective in reaching the target site. In this context, the present study aimed to isolate, characterize and evaluate the reproductive potential of the native strains of entomopathogenic nematode, Heterorhabditis indica against larval instars of S. frugiperda under laboratory conditions. Results Two strains of H. indica isolated and characterized from the rhizosphere of mango and curry leaf trees were designated as CICR-HI-MN and CICR-HI-CL, respectively. Both strains, CICR-HI-CL and CICR-HI-MN showed differential mortality against 3rd (LC50 value of 21.65, 48.91 IJs/larva), 4th (LC50 value of 25.46, 52.36 IJs/larva) and 5th (LC50 value of 59.20, 71.04 IJs/larva) instar larvae of S. frugiperda, respectively. The instar-wise mortality of S. frugiperda showed that 3rd instar was relatively more susceptible compared to 4th and 5th instar larvae. In terms of efficacy, CICR-HI-CL was almost twice effective than CICR-HI-MN when LC50 and LC95 values of 3rd instar larvae were compared. However, the reproductive potential of both the strains was significantly higher against 5th instar than the 3rd and 4th instar larvae. Strain CICR-HI-CL was more effective in larval mortality, while nematode reproduction was higher in CICR-HI-MN. Conclusions Native strains of H. indica evaluated in the present study were found effective against larval instars of fall armyworm, S. frugiperda. Higher reproduction on 5th instar larvae demonstrates the ability of these strains to multiply, sustain and perpetuate on late instars of this polyphagous pest and may serve as viable option in integrated pest management program.

The Lesser Chestnut Weevil (Curculio sayi): Damage and Management with Biological Control Using Entomopathogenic Fungi and Entomopathogenic Nematodes.

The lesser chestnut weevil, Curculio sayi (Gyllenhal), can cause irreparable damage to chestnuts through direct consumption and/or introduction of secondary pathogens. With the resurgence of blight resistant American Chestnut plantings both for commercial production and for habitat restoration, C. sayi has become a similarly resurgence pest. Here, we investigated the nature and extent of C. sayi larval damage on individual nuts and collected harvests with an eye toward the quantifying impacts. Next, we explored management options using biological control including entomopathogenic fungi and entomopathogenic nematodes. Nut damage from C. sayi can be extensive with individual nuts hosting several larvae, larvae emerging from nuts several weeks post harvest, and nut weight loss even after C. sayi have emerged from the nut. Applications of entomopathogenic fungi reduced chances of chestnut infestation, while certain strains of entomopathogenic nematodes increased the probability of C. sayi larval mortality. Understanding C. sayi damage and exploring biological control management options could be a useful tool in the effective management of this resurgent pest.