Entomopathogenic Nematode Populations Research Articles

Effectiveness of four Turkish entomopathogenic nematode isolates against Bactrocera oleae (Diptera: Tephritidae) pupae at different temperatures

Türkiye, is the country of origin of the olive tree and is among the world’s leading olive producers. Most of the olive production in Türkiye is concentrated in Izmir, Aydın, Çanakkale, Balıkesir, Muğla and Bursa Provinces. Bactrocera oleae (Diptera: Tephritidae), being one of the main pests of olive trees, is an important problem in olive cultivation in Türkiye. The efficacy of four Turkish populations of entomopathogenic nematodes against B. oleae pupae was determined under laboratory conditions. They were Steinernema feltiae/12, S. carpocapsae/1133, Heterorhabditis bacteriophora/70, H. bacteriophora/91, which were collected in different regions of Türkiye during our earlier studies. They were tested against the pest by using a single dose at 5 different temperatures (10, 15, 20, 25 and 30 °C). The highest infection rate was observed forH. bacteriophora/91 isolate at 25 °C, and the lowest infection rate was observed for S. feltiae/12 isolate at 10 °C.

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.

Effectiveness of Two Entomopathogenic Nematodes (Nematoda: Rhabditida) Populations in Controlling Fall Armyworm [(Spodoptera Frugiperda) Lepidoptera: Noctuidae] on Maize

The fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a recent invasive pest significantly impacting maize production and food security in sub-Saharan Africa. While chemical insecticides have offered the most effective control in Ghana, their detrimental effects on human health and the environment necessitate the urgent exploration of alternative, environmentally friendly options. This study compared two entomopathogenic nematodes populations, Heterorhabditis bacteriophora and Steinernema carpocapsae, against a control group (no application) for their efficacy in managing fall armyworm on maize. In the second experiment, S. carpocapsae significantly outperformed both H. bacteriophora and the control in terms of seed weight, achieving a 12.9% increase over the former and a remarkable ninefold improvement over the latter. The first experiment, however, showed no significant difference in seed yield (59 g, 32 g, 2 g) between the two nematode treatments, S. carpocapsae demonstrated the highest yield within this group. Notably, the control group exhibited the highest degree of foliage damage (4.7; 5.0) on a 1-5 scale throughout the study period. Overall, this study demonstrates the superior efficacy of S. carpocapsae compared to H. bacteriophora in controlling fall armyworm on maize. These findings provide valuable understandings for advancing the practical application of entomopathogenic nematodes as a sustainable and eco-friendly biocontrol measure against this devastating pest, contributing to enhanced food security in sub-Saharan Africa.

Eksplorasi, Identifikasi, dan Karakterisasi Nematoda Entomopatogen Pada Lahan Jagung dan Padi

Entomopathogenic nematodes (EPN) are potential nematodes as biological agents because they actively search for insect pests and are parasitic on their hosts. Two genera of EPN can be used as biological agents: Steinernema and Heterohabditis. It is necessary to explore local EPN on land suspected of having potential as a habitat for the nematodes. This study aimed to determine the genus and population of the EPN from corn and rice farms in Jember by identifying and characterizing them. The method used was the descriptive method. The EPN population was analyzed using the T-test. The results showed that the EPN from the corn and rice fields belonged to the Steinernema genus. EPN from the corn field isolate was characterized by a body length of 826,77 μm, body width of 47.14 μm, and tail length of 73.16 μm, while from the rice field, the isolate was characterized by a body length of 840.54 μm, body width of 37.70 μm, tail length 57.52 μm. EPN populations in maize and rice fields were not significantly different.
 
 Keywords: exploration, entomopathogenic nematodes, Steinernema

Exploration of Entomopathogenic Nematodes in Organic Rice Field in Sleman Regency

Entomopathogenic nematodes (EPNs), consisting of genera Steinernema and Heterorhabditis are biological agents proven effective in killing insect pests. Organic rice fields and sandy soil textures are potential areas for exploring the presence of EPNs. This research aims to determine the diversity of genera and populations of entomopathogenic nematodes in organic rice fields in Sleman Regency. The study was conducted on organic rice fields and the UPN "Veteran" Yogyakarta Plant Protection Laboratory from July – August 2023. EPNs were obtained from Prambanan Sleman and Ngemplak Sleman, with six plots as sample units in every location. EPNs were isolated from soil samples by using Tenebri molitor larvae. The Whitehead tray method was used to isolate EPNs from the dead larvae, and the population of EPNs was counted. EPNs were identified based on the symptoms of color changes on the cuticle and morphological characters. The result showed that the cuticles of T. molitor larvae that died were blackish brown in Prambanan and Ngaliyan isolates, referred to Steinernema genera. EPNs were found in Prambanan_6, Ngaliyan_1, and Ngaliyan_2. The highest population of EPNs was on Ngaliyan_1 (38,00 EPNs/ml), and the lowest was on Prambanan_6 (2,13 EPNs/ml). Based on the morphological characters of EPNs, on the Prambanan_4, Ngaliyan_1, and Ngaliyan_2, EPNs were identified as Steinernema spp. The characteristics of Steinernema in the infective juvenile stage found are: slender body, anterior end slightly rounded and fused with the body, cylindrical stoma, no second cuticular sheath, not annulated, and conoid tail.

The efficacy of Steinernema feltiae in the control of Cydia pomonella in organic apple and pear orchards of Patagonia Argentina and its impact on local populations of entomopathogenic nematodes

The efficacy of Steinernema feltiae in the control of Cydia pomonella in organic apple and pear orchards of Patagonia Argentina and its impact on local populations of entomopathogenic nematodes

Entomopathogenic Nematode Compatibility with Vineyard Fungicides.

Vineyards, covering over seven million hectares worldwide, hold significant socio-cultural importance. Traditionally reliant on conventional practices and agrochemicals, this agroecosystem faces environmental challenges, including soil and water pollution. Sustainable viticulture, driven by eco-friendly practices and cost reduction, has gained prominence, underlining the importance of biological control agents such as entomopathogenic nematodes (EPNs). EPNs naturally occurr in vineyard soils and play a crucial role in controlling pest damage. Ensuring compatibility between EPNs and the commonly used vineyard fungicides is critical, as these applications constitute the predominant pest-management practice during the productive grapevine cycle. This study assessed the impact of authorized grapevine fungicides on EPNs, focusing on the survival of populations and sublethal effects on their virulence. We investigated the compatibility of two EPN populations (Steinernema feltiae 107 and S. carpocapsae 'All') with three organic production-approved products (Bacillus pumilus, sulfur, and copper oxychloride) and two synthetic chemicals (Trifloxystrobin and Mancozeb). Our findings revealed that the viability of S. feltiae 107 was reduced when exposed to sulfur and copper oxychloride, and its virulence was affected by copper oxychloride and Mancozeb, although only two days after exposure and with no significant differences for larval mortality at five days. In contrast, S. carpocapsae 'All' exhibited full compatibility with all five fungicides, with no impact on its viability or virulence. Consequently, our results suggested that the evaluated fungicides could be co-applied on both EPN populations if they were employed on the same day. However, further research on multi-target interactions is needed to ensure the successful implementation of this kind of co-application.

Multigene Sequence-Based and Phenotypic Characterization Reveals the Occurrence of a Novel Entomopathogenic Nematode Species, Steinernema anantnagense n. sp.

Three entomopathogenic nematode populations were isolated from agricultural fields in the Anantnag district of Jammu and Kashmir (India). Sequences of multiple gene regions and phenotypic features show that they are conspecific and represent a novel species. Molecular and morphological features provided evidence for placing the new species into the "Kushidai" clade. Within this clade, analysis of sequence data of the internal transcribed spacer (ITS) gene, the D2D3 region of the 28S rRNA gene, the mitochondrial cytochrome oxidase I (mtCOI) gene, and the mitochondrial 12S (mt12S) gene depicted the novel species as a distinctive entity closely related to Steinernema akhursti, S. kushidai, and S. populi. Phylogenetic analyses also show that the new species is a sister species to S. akhursti, and these two species are closely related to S. kushidai and S. populi. Additionally, the new species does not mate or produce fertile progeny with any of the closely related species, reinforcing its uniqueness from a biological species concept standpoint. The new species is further characterized by the third-stage infective juveniles with almost straight bodies (0.7-0.8 mm length), poorly developed stoma and pharynx, and conoid-elongate tail (49-66 µm) with hyaline posterior part. Adult females are characterized by short and conoid tails bearing a short mucron in the first generation and long conoid tails with thin mucron in the second generation. Adult males have ventrally curved spicules in both generations. Moreover, the first-generation male has rounded manubrium, fusiform gubernaculum, conoid and slightly ventrally curved tails with minute mucron, and the second generation has rhomboid manubrium anteriorly ventrad bent, and tails with long and robust mucron. The morphological, morphometrical, molecular, and phylogenetic analyses support the new species status of this nematode, which is hereby described as Steinernema anantnagense n. sp. The bacterial symbiont associated with S. anantnagense n. sp. represents a novel species, closely related to Xenorhabdus japonica. These findings shed light on the diversity of entomopathogenic nematodes and their symbiotic bacteria, providing valuable information for future studies in this field.

Characterization of Steinernema feltiae (Rhabditida: Steinernematidae) Isolates in Terms of Efficacy against Cereal Ground Beetle Zabrus tenebrioides (Coleoptera: Carabidae): Morphometry and Principal Component Analysis.

One of the most dangerous pests of cereals is Zabrus tenebrioides and, in Poland, it is becoming a serious pest. Entomopathogenic nematodes (EPNs) seem to be a very promising, biological control agent for this pest. Native EPN populations are well adapted to local environmental conditions. The current study characterized three Polish isolates of the EPN Steinernema feltiae, which differed in their effectiveness against Z. tenebrioides. In the field, isolate iso1Lon reduced the pest population by 37%, compared with 30% by isolate iso1Dan and 0% by the iso1Obl isolate; the number of plants damaged by Z. tenebrioides in the presence of the different isolates reflected the results in terms of the decrease in pest population size. After incubation in the soil for 60 days, recovered EPN juveniles of all three isolates were able to infect 93-100% of the test insects, with isolate iso1Obl again showing the lowest effectiveness. The juveniles of isolate iso1Obl were also morphometrically distinct from the other two isolates, as revealed by principal component analysis (PCA), which helped to distinguish the EPN isolates. These findings showed the value of using locally adapted isolates of EPNs; two of the three isolates randomly selected from Polish soil outperformed a commercial population of S. feltiae.

Effect of storage media and temperature on viability and pathogenicity of North Indian populations of entomopathogenic nematodes

Effect of storage media and temperature on viability and pathogenicity of North Indian populations of entomopathogenic nematodes

Irrigation modulates entomopathogenic nematode community and its soil food web in olive groves under different agricultural managements

Entomopathogenic nematodes (EPNs) are biological control agents distributed worldwide in natural and agricultural soils. Recent evidence supports the hypothesis that stable rhizospheres of perennial crops can favor the occurrence of EPNs. However, different agricultural management practices can modulate their natural distribution in agroecosystems, hence should be considered in conservation biological control programs to support as high as possible native EPN populations. Cultivated olive (Olea europaea subsp. europaea), originally from the Mediterranean Basin, is a key perennial crop susceptible to a diverse range of arthropod pests that account for their life with at least one soil inhabitant stage. In this study, we investigated, for the first time, the occurrence of EPNs and associated soil organisms in olive groves managed with different practices. We surveyed 89 commercial olive groves located in Andalusia (Southern Spain) and differently handled for pest management (conventional vs. organic), soil management (tilling vs. cover cropping), and irrigation regime (rain feed vs. drip-irrigation). By using species-specific primers-probe sets and quantitative real-time PCR approaches, we screened the occurrence of nine species of EPNs, five free-living nematodes (FLNs), and six nematophagous fungi (NF). We found EPNs in 23.6% of the sites, identifying only two EPN species: Steinernema feltiae (15.7%) and Heterorhabditis bacteriophora (7.9%). Pest and soil management did not affect EPN abundance, but drip irrigation increased their occurrence (P < 0.025). On the contrary, we recorded lower FLN numbers in irrigated groves (P = 0.003), particularly for Oscheius tipulae and Pristionchus maupasi. Regarding NF, both organic management (P < 0.001) and drip irrigation (P < 0.035) enhanced their abundance. Four abiotic explanatory variables (extractable P, clay content, elevation, and precipitation) explained 85.6% of the EPN, FLN, and NF species variation in multivariate analysis. Overall, drip irrigation in the olive groves enhanced the EPN community but also NF growth, natural enemies of nematodes. Additional studies are required to determine the best combination of alternative strategies that will enhance a balanced soil biota in olive groves in Mediterranean regions and other areas where this crops is cultivated that enable conservation ecosystem services, such as those provided by the EPNs.

Invasion of Popillia japonica in Lombardy, Italy: Interactions with soil entomopathogenic nematodes and native grubs

Abstract The recent invasion of the Japanese beetle Popillia japonica Newman (Coleoptera: Scarabaeidae) in northern Italy offered the opportunity to explore the entomopathogenic nematodes (EPNs) associated with the soil of hay meadows. A total of 61 sites were considered for nematode sampling, and from 17 of them (27.9%) EPNs were isolated and further characterized with molecular and morphological techniques as well as with laboratory bioassays. Two main species, Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) and Steinernema carpocapsae Weiser (Rhabditida: Steinernematidae) were recorded with the same frequency together with a few other species (Rhabditida: Oscheius sp. and Phasmarhabditis sp.). The newly isolated EPN populations were characterized for their activity (penetration rate) and infectivity to P. japonica grubs. EPNs occurrence was related to the time of beetle invasion at each sampling site and there was evidence of a density‐dependent response of the EPNs community to P. japonica density. The invasion of P. japonica apparently did not significantly affect the occurrence of native grubs, although a tendency to a decline was observed and should be further investigated.

Populations of entomopathogenic nematodes in agricultural lands

Entomopathogenic nematodes (EPNs) are known agents in pest biological control. Environmental factors can influence on populations of soil-inhabitant nematodes like EPNs in agricultural lands. In the current study, after selecting a suitable study site (33.20-33.42 N and 48-48.55 E), and soil sampling (250 samples) in May to July 2019, infectious juveniles of EPNs were extracted from soil samples according to the bait method. According to occurrence of EPNs-infected Galleria mellonella larvae, natural occurrence (%) of EPNs was estimated, while considering soil characteristics (salinity and acidity), region (altitude) and type of crop. Also, population incidence (%) of EPNs in EPNs-positive soil samples was estimated, according to G. mellonella larvae mortality by re-baiting. As results, seven soil samples were found to be EPNs-positive per total samples. Natural occurrence (%) of EPNs, Steinernematidae and Heterorhabditidae was equal to 2.8, 2, and 0.8%, respectively. This was variable under ranges of area altitude, soil salinity and acidity, and crop type, so that the highest to lowest occurrence (%) of EPNs was observed in forage crops (4%), vegetables (4%), industrial crops (4%), fruit trees (2%), and cereals (1.33%), respectively. There was a significant difference (P<0.05) in incidence of EPNs҆ population (%) in EPNs-positive samples. The lowest-highest incidence of EPNs҆ population was obtained as 15.52-33.4% in 7 EPNs-positive samples. As a conclusion, type of crop, altitude and soil acidity and salinity play a role in the level of occurrence and incidence of EPNs populations. These may have affected the biological and ecological properties of the nematodes populations.

The lure of hidden death: development of an attract-and-kill strategy against Agriotes obscurus (Coleoptera: Elateridae) combining semiochemicals and entomopathogenic nematodes

Wireworms are polyphagous soil-dwelling pests that are hard to control. Attract-and-kill strategies, combining attractive semiochemicals with biocontrol agents, have great promise to control insect pests. We hypothesized that the combination of plant semiochemicals and entomopathogenic nematodes (EPNs) in an attract-and-kill system could greatly enhance the nematodes' efficiency against wireworms. We evaluated the potential of alginate beads loaded with plant extracts and EPNs to control Agriotes obscurus. We tested the efficiency to kill wireworms or to reduce their feeding activity when combining potato tuber extracts as attractants with any of seven different EPN populations. While a direct application of EPNs on wireworms did not reduce the feeding activity nor increased their mortality, the combination of attractants and EPNs encapsulated in alginate beads resulted in attraction and consumption of the EPNs and caused up to 50% wireworm mortality with the EPN species Steinernema carpocapsae. Beads with EPNs caused a significant reduction of the wireworms' feeding activity. This study shows that wireworms feeding on EPN-containing beads have their feeding activity and survival negatively affected. Considering their long developmental time and the survival capability of EPNs in the soil, implementing this attract-and-kill system in the field might be a suitable strategy for the long-term management of wireworms.

Influence of Different Species of Steinernema and Heterorhabditis on Galleria mellonella and Spodoptera littoralis

Entomopathogenic nematodes (EPNs) can be used efficiently as biological control agents against specific insects. Galleria mellonella (Gm) and Spodoptera littoralis (Sl) are considered important agricultural pests. The aim of this study was to evaluate the susceptibility of their larvae to ascending levels of four species of EPNs, Steinernema carpocapsae (Sc), S. arenarium (Sa), Heterorhabditis bacteriophora (Hb) and H. indica (Hi) as well as the ability of nematodes to penetrate and reproduce within their hosts. Fifth larval instar of Gm and Slwere used to evaluate the effect of four inoculum doses [200,400,800, and 1600 infective juveniles (IJs)] of each nematode species. Percentage of insect mortality (% M) and the nematode-rate of reproduction (Rr) were calculated after 24 and 48 hrs. The data confirmed that H. bacteriophora was the highest effective species on both insects. The % M was 75.7, 79.7, 82.3, and 83% after 24 hrs and 98.0, 99.3,100 and 100% after 48 hrs in Gm for these doses, respectively. On the other hand, the corresponding mortalities were 75.0, 78.3, 81.7, and 83.8% after 24 hrs and 97.3, 98.3, 100 and 100% after 48 hrs in Sl. The highest initial EPN population that could penetrate the insect (pi) was achieved by HbinGm (295 IJs) at 1600 IJs, while it was 221.7 IJs in Sl larvae at the same inoculum. The highest final population and Rr were obtained at the inoculum level of 200 and 400 IJs. in Gm and Sl, respectively.The study documented that Heterorhabditis and Steinernema can be used effectively in Gmand Sl management. Moreover, Hb is the most suppressive species tested against the two lepidopteran hosts.

Evaluation of Native Entomopathogenic Nematode Isolates for the Management of Selected Insect Pests in Nigeria

Native entomopathogenic nematodes (EPNs) were evaluated for the management of three selected pests, Sesamia calamistis, Spodoptera frugiperda and Rhynchophorus ferrugineus in laboratory bioassays. The EPNs were isolated from soils from various locations within Ibadan, Nigeria using the greater wax moth (Galleria mellonella) as insect bait. A two-factor laboratory experimental assay was laid out in a completely randomized design and replicated three times. The EPN suspension was applied on insect larvae with distilled water as control. Number of days to mortality, percentage mortality of insect larvae, and total EPN population of infective juveniles (IJs) recovered from larval cadavers were assessed and reproductive factor (RF) determined. Data were analyzed using analysis of variance, and means were separated using Tukey’s Studentized Range Test at P G. mellonella (5075.08), >S. frugiperda (3957.23), >S. calamistis (742.31). From the results, EPN had the greatest fecundity in G. mellonella and R. ferrugineus showing higher ability to be recycled. This study reveals the potential of native EPNs as a biocontrol agent of insect pests and emphasizes the need for a more environment-friendly and sustainable approach to insect pest management.

Quantification of pH tolerance levels among entomopathogenic nematodes.

Soil pH affects the availability of nutrients, which impacts plant growth and development. Similarly, soil pH may also influence microorganisms in the soil, either beneficial or nonbeneficial. One such group of beneficial microorganisms is entomopathogenic nematodes (EPN), parasites of soil-inhabiting insects. Entomopathogenic nematodes have a number of attributes that make them good alternatives to chemical insecticides. The objective of this study was to investigate pH tolerance of 11 steinernematids and six heterorhabditids post exposure to different pH levels. Entomopathogenic nematode populations were exposed to varying pH levels (pH2 to pH11) made up from two different chemical solutions (ammonium-acetate and citrate-phosphate). Entomopathogenic nematode populations are expected to have varying tolerance to different pH levels. The highest infective juvenile survival was obtained from pH3 to pH10 in citrate-phosphate, where all populations displayed >50% survival. Steinernema carpocapsae populations had >90% survival at pH3 to pH11 in citrate-phosphate solutions. Overall, the steinernematids had a higher survival range in ammonium-acetate pH solutions compared with the heterorhabditids. Moreover, Steinernema spp., S. carpocapsae (ScCxrd, ScAll, and ScItalian) and S. riobrave showed consistently higher survival in both acidic and alkaline solutions, when compared to the other steinernematids, suggesting that they may be applied in both acidic and alkaline soils. These findings can be of use when selecting EPNs for biological control purposes in the two countries, respectively.

Entomopathogenic nematode management of small hive beetles (Aethina tumida) in three native Alabama soils under low moisture conditions.

The goal was to determine the efficacy of entomopathogenic nematodes (EPNs) on Aethina tumida small hive beetle (SHB) in Alabama soils. The objectives were to (i) determine the pupation success of SHB wandering larvae; (ii) determine the efficacy of EPNs on SHB wandering larvae in natural and autoclaved soil; and (iii) determine the efficacy of EPNs on SHB wandering larvae in three Alabama soil types at typical low moisture levels. The Alabama soils were Kalmia loamy sand (KLS), Benndale fine sandy loam (BFSL), and Decatur silt loam (DSL). Heterorhabditis bacteriophora, H. indica, Steinernema carpocapsae, S. feltiae, S. kraussei, and S. riobrave were tested at population densities of 5, 10, 20, 40, and 80 third-stage infective EPN juveniles (IJ3) per 130 cm3 soil. Pupation success in SHB population densities of 5, 10, and 20 wandering larvae per Petri dish were similar. Of the six EPN species, S. carpocapsae achieved the highest efficacy across all EPN population densities in both natural and autoclaved soil. Steinernema riobrave and H. indica achieved the next highest efficacies; however, they were significantly less effective than S. carpocapsae. Steinernema carpocapsae parasitized 87% SHB wandering larvae across all population densities tested. Steinernema carpocapsae achieved the best efficacy colonizing 94% of the SHB in the KLS soil, 80% in the BFSL soil, and 47% in the DSL soil. In conclusions, S. carpocapsae is be a promising biological control EPN to implement into a management system on SHB.

Evaluation of indigenous entomopathogenic nematodes in Southwest China as potential biocontrol agents against Spodoptera litura (Lepidoptera: Noctuidae).

Spodoptera litura is a notorious leaf feeding insect pest in the Asia-Pacific region and leads to a significant economic loss in vegetable and field crop production. Entomopathogenic nematodes (EPNs), lethal parasites of insects, are used as biocontrol agents. Yunnan Province in China is a well-known region due to its rich biodiversity. In the present study, a survey of EPNs using the Galleria-baiting technique was conducted in 2017 and 2018 throughout the entire Yunnan province. In total, 789 soil samples were collected from 232 sites, of which 75 samples were positive for EPNs. Phylogenetic analyses of ITS, D2D3 expansion region of the 28S rRNA gene, as well as mitochondrial cytochrome c oxidase subunit I (COI), were performed to identify isolated nematode species and evaluate their genetic diversity. In total, 13, 3, and 58 identified populations belong to Steinernema, Heterorhabditis, and Oscheius, respectively. The phylogenetic relationships of EPN species in the three genera were analyzed with the Neighbor-Joining method. The virulence of the trapped isolates in the genera of Steinernema, Heterorhabditis, and Oscheius against S. litura was evaluated. Ten new indigenous isolates from Steinernema and Heterorhabditis showed prominent virulence to S. litura within 48 hr which is equivalent to that of commercial EPNs populations. The present study provides background information on indigenous EPN resources for S. litura control in Asia-Pacific region.

Comparison of virulence, reproductive potential, and persistence among local Heterorhabditis indica populations for the control of Temnorhynchus baal (Reiche & Saulcy) (Coleoptera: Scarabaeidae) in Egypt

The scarab beetle, Temnorhynchus baal (Reiche & Saulcy) (Coleoptera: Scarabaeidae), becomes a key pest of strawberry, especially after increasing its cultivated area and economic importance in Egypt. Few entomopathogenic nematode (EPN) species/strains were tested against this pest, where only a foreign species had good effect comparable to the native populations tested previously. Thirty-eight indigenous Heterorhabditis indica populations were tested against the most damaging, third instar larvae of H. baal in two soil types, where strawberry cultivation prevails. The corrected mortality induced by indigenous H. indica population in T. baal larvae was (99.52 and 98.57%) for 15 populations in the sandy soil and 23 in loamy sand soil, respectively. Overall average of infective juveniles (IJs) per T. baal larva was about (41,000). The average of emerged nematode-IJs from the infected grubs for the 15 EPN populations in sandy soil, (46,960 IJs/grub), was significantly (P < 0.001) higher than that (36,502 IJs/grub) of 23 EPN populations in loamy sand soil. The insignificant difference was detected in the reproductive capacity among nematode populations in T. baal larvae in sandy or loamy sand soil. A highly significant difference was found among total IJ numbers collected 10, 18, 26, and 30 days post-inoculation in sandy or loamy sand soil. The persistence of the H. indica populations in the soil varied greatly. Obtained results suggest further use of at least ten populations of such indigenous nematodes under field conditions.