Application 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.

Preferences for livestock bedding as a development substrate of the stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), and potential application of entomopathogenic nematodes for controlling stable fly larvae.

The stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), is a significant insect pest with global veterinary implications due to its capacity to both cause nuisance and transmit disease-causing pathogens to livestock. This study aimed to determine the livestock bedding preferred for use as a development substrate by S. calcitrans larvae and field-collected adults. The result showed that S. calcitrans larvae exhibited a preference (26.7%) for 7-day-old cow manure. Gravid females displayed a pronounced preference (55.0%) for fresh cow manure. As there were eight choices, indifference would result in 12.5% for each bedding substrate. Furthermore, the efficacy of four entomopathogenic nematodes (EPNs), namely Heterorhabditis bacteriophora (Poinar), Heterorhabditis indica Poinar, Karunakar & David (Rhabditida: Heterorhabditidae), Steinernema siamkayai Poinar, Karunakar & David and Steinernema carpocapsae (Weiser) (Rhabditida: Steinernematidae), against S. calcitrans larvae and the persistence after application to livestock bedding substrates were evaluated under laboratory conditions. In filter paper bioassays, all four EPNs caused 76.7%-100.0% mortality in the second instar larvae of S. calcitrans when applied at 50 and 100 infective juveniles (IJs)/cm2 within 5 days after exposure. For the third instar larvae of S. calcitrans, only H. indica induced high mortalities of 86.6% when applied at 100 IJs/cm2 within 5 days after exposure, while the other EPNs resulted in mortalities of less than 70%. The data further demonstrated that H. bacteriophora, H. indica and S. siamkayai remained present in the substrates linked to S. calcitrans larvae for as long as 7 days after the application of EPNs. This study demonstrates the potential of EPNs as a biologically based control agent against larvae of S. calcitrans, a serious pest and significant vector for various livestock animals.

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

The application of entomopathogenic nematode modified microbial communities within nesting mounds of the red imported fire ants, Solenopsis invicta

Entomopathogenic microorganisms (e.g., fungi, bacteria, nematodes) have been widely used in biological control of soil-dwelling pests, including the red imported fire ant (RIFA), Solenopsis invicta, a notorious invasive pest worldwide. The application of large amounts of entomopathogenic microorganisms to soil may affect the indigenous soil microbial communities. However, reports about the effect of entomopathogenic nematodes (EPN) on soil microbial communities are very few. In this study, the effects of EPN on RIFA populations and microbial communities in mounds were investigated. Our results showed that the application of the EPN Steinernema carpocapsae. All strain on mounds efficaciously suppressed RIFA worker populations, without forming significantly more satellite mounds compared with the control treatment. The application of EPN did not impact the bacterial and fungal diversity in soils derived from the RIFA mounds. However, it slightly altered the taxonomic make-up of the bacterial communities, but significantly altered the taxonomic composition of fungal communities at the phylum, family, and genus levels. The abundances of some beneficial bacteria and fungi, such as Streptomyces, decreased, while those of plant and animal pathogenic bacteria and fungi, dramatically increased, after EPN treatment. On the other hand, the abundances of some entomopathogenic fungi, such as Fusicolla, Clonostachys, and Mortierella, increased. Redundancy analysis or canonical correspondence analysis revealed a positive correlation between the efficacious EPN control and the presence of the insect-resistant bacteria, Sinomonas, as well as entomopathogenic fungi Fusicolla and Mortierella. This suggests that the interactions between EPN and entomopathogenic fungi may play a role in the biological control of RIFA. Our discoveries shed light on the interactions among EPN, RIFA, and soil microbial communities, and emphasize a possible mutualistic relationship between EPN and entomopathogenic fungi in the biological control of RIFA.

Standardizing in-vivo mass production technique for entomopathogenic nematode Heterorhabditis bacteriophora (Nematoda: Heterorhabditidae)

Biological control is a need of hour to protect crops in a sustainable manner without disturbing ecological balance. Entomopathogenic nematodes (EPNs) have a potential to be used effectively and selectively as inoculative agents for classical biological control. EPNs production can be done in both in vivo and in vitro. In vivo method was preferred during present studies aimed at standardizing mass production technology for Heterorhabditis bacteriophora that can easily be adopted at small scale farms. Different cost-effective diets used for rearing Galleria mellonella (GWM) (Lepidoptera: Pyralidae) were standardized to show their effect on development and production of in vivo mass production of EPNs on GWM larvae. Diet consisting of maize flour (400 g), wheat flour, wheat bran, milk powder (200 g each), yeast (100 g), glycerol (350 ml) and honey (350 ml) was found best among all the diets tested for rearing GWM with 93.5 percent larvae surviving to cocoon formation stage and average larval weight of ca 300 mg for inoculating 5 GWM larvae in 50 mm diameter inoculation arena, 0.5 ml of formalin solution (0.1 percent) was found to create optimum moisture in the arena to give quick mortality of GWM. The inoculation dose (200 ± 2.1 IJs/larva) of EPNs and temperature of 20 °C were found to give highest harvest of infective juveniles (IJs/larva) from the host. Enhanced effectiveness of EPN application can be assisted through advanced diet which is most significant factor influencing consistent development of GWM in turn affecting EPNs maximum harvest.

Exploring entomopathogenic nematodes for the management of Lobesia botrana (Lepidoptera: Tortricidae) in vineyards: Fine-tuning of application, target area, and timing

Lobesia botrana (Lepidoptera: Tortricidae) is a crucial grapevine pest worldwide. Expanding the available biocontrol agents can provide new management strategies compatible with organic viticulture. Entomopathogenic nematode (EPN) potential as a biocontrol agent was demonstrated against various developmental stages of L. botrana. For its field application, we hypothesised that by selecting the best combination of EPN-adjuvant and identifying the best area/timing for their application, we will secure their effective implementation against L. botrana. The aim of this study was to determine the best ecological scenarios for their use against L. botrana. We investigate three EPN species naturally occurring in Riojan vineyards: Steinernema feltiae, S. carpocapsae, and Heterorhabditis bacteriophora. We evaluated (i) EPN viability, infectivity, and adherence on leaves combined with adjuvants (Multi-Us, Maximix, Dash HC, Nu-Film-17, and Adrex), (ii) EPN biocontrol against L. botrana larva on leaves and grapes and damage reduction, and (iii) EPN efficacy against L. botrana at 22°, 15°, and 10 °C. Overall, all the adjuvants were compatible with the EPN, except Adrex with Heterorhabditis bacteriophora. Compared with the no application, EPNs (steinernematids) alone or with Maximix increased L.botrana L3 mortality on grapes and leaves, thereby reducing the damage. Pupal mortality caused by steinernematids EPN (alone or with Maximix) decreased with temperature, from ∼60% at 22 °C to <30% at 10 °C. Overall, steinernematids EPN (alone or with Maximix) applied against L. botrana on leaves, grapes, or trunks reduced the damage and increased insect mortality. This study suggests the best-case scenario for the application of EPNs is at sunset during late spring/early autumn at mid-temperatures (22 °C-15 °C). Further field validation is necessary for their full implementation.

Sensitivity of Yponomeuta padella and Yponomeuta cagnagella (Lepidoptera: Yponomeutidae) to a Native Strain of Steinernema feltiae (Filipjev, 1934)

The larvae of ermine moths from the Yponomeutidae family (Lepidoptera) feed on a range of species and varieties of fruit and ornamental trees. Some species of this family pose a serious threat to the environment, mainly because of the significant defoliation they cause but also due to the widespread use of insecticides used to control them. This study was designed to assess the sensitivity of Yponomeuta padella and Yponomeuta cagnagella larvae and pupae to a native strain of Steinernema feltiae ZAG15 nematodes under laboratory conditions and to test the biological activity of these nematodes against the larvae and pupae of these species in field studies. The following doses were used in the laboratory tests: 50 IJs/insect (Petri dish tests) and 100 IJs/insect (container tests). Petri dish and container tests were performed at 20 °C and 60% humidity. Mortality of two stages (larvae and pupae) was determined 3 days after treatment. In the field trials, the nematodes were applied at the following doses: 4000 IJs/web for the caterpillars of Y. padella and Y. cagnagella and 1000 IJs/web for the pupae of Y. padella and Y. cagnagella (this corresponded to approximately 200 IJs/insect). Nematodes were applied using a 1 L hand sprayer and a lance. The efficacy of the application was assessed after seven days. The results of our study showed that the larvae (81.7%) and pupae (88.3%) of Y. padella had a greater susceptibility to entomopathogenic nematodes (EPNs) than those of Y. cagnagella (50% and 33.3%, respectively). However, our promising laboratory results did not translate into results in field trials, where the application of EPNs proved to be ineffective.

Biocontrol potential of entomopathogenic nematodes against invasive fall armyworm, Spodoptera frugiperda in India

The invasion of fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), has threatened the researchers to develop an effective biological control strategy at the global level. Larval stage remains in maize whorl, and precise placement of entomopathogenic nematodes (EPNs) opens up wide opportunity for biological control. The study evaluated the virulence of Heterorhabditis indica (Poinar) and Steinernema carpocapsae (Weiser) against all the developmental stages of S. frugiperda. The results revealed that both the tested EPNs had a high rate of ovicidal, larvicidal and pupicidal effects on S. frugiperda. The EPNs also significantly affected the adults, resulting in the deformation and death. The invasion efficiency and reproduction assays of EPNs revealed that H. indica had higher invasion efficiency and reproduction rates compared to S. carpocapsae on different larval stages and pupae. EPNs also reproduced in the adult cadavers of S. frugiperda emerged from the EPN-treated pupa. A preliminary study on the effect of EPN application on S. frugiperda was carried out under semi-field conditions by pre-releasing third instar larvae to whorl of corn plants. Application of H. indica and S. carpocapsae @ 500 IJs mixed with five gram of sand was applied manually to whorl led to mortality of 86.67 and 83.33%, respectively. The study demonstrated that both the EPN species tested showed high puissance as bio-control agents against S. frugiperda, having the potential for its successful management.

Entomopathogenic Nematodes for Field Control of Onion Maggot (Delia antiqua) and Compatibility with Seed Treatments.

Onion maggot (Delia antiqua) is a prominent pest of allium crops in temperate zones worldwide. Management of this pest relies on prophylactic insecticide applications at planting that target the first generation. Because effective options are limited, growers are interested in novel tactics such as deployment of entomopathogenic nematodes. We surveyed muck soils where onions are typically grown to determine if entomopathogenic nematode species were present, and then evaluated the compatibility of entomopathogenic nematode species with the insecticides commonly used to manage D. antiqua. We also evaluated the efficacy of these entomopathogenic nematodes for reducing D. antiqua infestations in the field. No endemic entomopathogenic nematodes were detected in surveys of muck fields in New York. Compatibility assays indicated that, although insecticides such as spinosad and, to some extent, cyromazine did cause mortality of entomopathogenic nematodes, these insecticides did not affect infectivity of the entomopathogenic nematodes. Field trials indicated that applications of entomopathogenic nematodes can reduce the percentage of onion plants killed by D. antiqua from 6% to 30%. Entomopathogenic nematodes reduced D. antiqua damage and increased end of season yield over two field seasons. Applications of entomopathogenic nematodes may be a viable option for reducing D. antiqua populations in conventional and organic systems. Together with other management tactics, like insecticide seed treatments, applications of entomopathogenic nematodes can provide a yield boost and a commercially acceptable level of D. antiqua control.

Combined effect of entomopathogenic nematode, Heterorhabditis indica with entomopathogenic fungi, Metarhizium pinghaense and M. robertsii against the obscure mealybug, Pseudococcus viburni

In this study, we evaluated the combined application of entomopathogenic nematodes (EPN), Heterorhabditis indica, with entomopathogenic fungi (EPF), Metarhizium pinghaense or M. robertsii, against Pseudococcus viburni (Signoret), in laboratory trials. Three EPF-EPN combinations were used, where P. viburni was either exposed to the EPF and EPN isolates simultaneously or sequentially, at different time intervals. The combined application of H. indica with each of the two EPF isolates resulted in higher mortality of P. viburni, under laboratory conditions, relative to when applied individually. With sequential application, the H. indica and M. robertsii combination was shown to be more effective, resulting in 85 ± 3.1% and 88.8 ± 3.9% mortality after four and three days, respectively. Heterorhabditis indica combined with M. pinghaense was more effective for simultaneous application of the entomopathogens, resulting in 95 ± 6.5% mortality after five days. Insect mortality was mostly due to EPN infection. The single application of H. indica against P. viburni resulted in 76.3 ± 2.9% after 48 h, while M. pinghaense and M. robertsii resulted in 73.8 ± 7.9% and 82.5 ± 3.3% respectively, after a week. Interactions between H. indica and the two EPF isolates were shown to have an additive effect, when used simultaneously and sequentially. The results from the study indicate that the combined application of EPF and EPN could potentially be used as an alternative strategy for management of P. viburni in fruit production areas.

Field application of encapsulated entomopathogenic nematodes using a precision planter

The use of entomopathogenic nematodes (EPNs) as a biological control agent in agriculture has shown efficacy against various soil-dwelling pests. Despite its potential, high production costs and inconsistent field efficiency remain significant challenges. Although EPNs can be applied using irrigation systems and spraying equipment, optimized applications are required. This study aimed to evaluate the feasibility of applying EPNs in gelatin capsules and planting with a precision planter. It was hypothesized that this method would lead to more controlled and uniform EPN application. The effects of EPN encapsulation on dispersal and field persistence in the soil were also investigated. Larval mortality for capsule applications was between 53 and 67% under field conditions, with no statistical difference compared to the drip irrigation applications. Dispersal trials were carried out using custom steel olfactometers, and capsule application did not have any adverse effects on the dispersal of infective juveniles for 24, 48 and 72 h. Persistence trials revealed no significant differences between the capsule and control groups, with a maximum persistence of 50 days. The results suggest that the capsule technique could be a promising option for large-scale EPN applications, and further optimization may lead to improved results.

Entomopatojen nematodların üç uygulama tekniği ile patates böceği [Leptinotarsa decemlineata (Say), (Coleoptera: Chrysomelidae)] üzerinde etkilerinin sera koşullarında araştırılması

Colorado Potato Beetle [Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)] (CPB) is one of the most destructive pests of potatoes. CPB is a polyphagous pest that damages every stage of the potato. Although entomopathogenic nematodes (EPNs) in the world have been demonstrated by many laboratories and field/garden studies activity against many harmful groups, very few studies have been conducted on CPB in our country (Türkiye). In the scope of work intended to be used EPNs against CPB. The main objective of the study is to reveal greenhouse-pot applications (soil, green limbs, and cadaver applications) of EPN [Steinernema feltiae (isolate 09-31) and Heterorhabditis bacteriophora (isolate 09-43)], which are present in our laboratories in our stocks. For the first time in Türkiye, greenhouse-pot applications studies have been carried out against this harmful group. There is also a lot of work in the world about the use of aqueous concentrations of EPNs against harmful effects. In recent years, efforts have been made to use EPNs in cadavers instead of aqueous concentrates. This application (cadaver applications) against CPB is the first working. The results revealed that EPNs performed better in soil applications, and the highest mortality rate was obtained from S. feltiae (65.23±4.45 and 77.33±2.59). Other applications (green limbs and cadaver applications) are seen to have a low level of efficacy. In trials, the mortality rate in cadaver applications did not exceed 40%, and the lowest mortality rate in H.bacteriophora was 37,40±8,88%. In the case of green devices, the mortality rate did not exceed 30%, and the highest mortality rate was 29.14±6.09 in H.bacteriophora. According to EPN greenhouse-pot experiments results, soil applications of S. feltiae (isolate 09-31) should be included within the scope of field trials.

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.

Entomopathogenic nematodes for the control of oriental fruit fly Bacterocera dorsalis (Diptera: Tephritidae)

BackgroundFruit fly species are most damaging pests around the globe which reduced the commercial value of fruits at maturity. Entomopathogenic nematodes (EPNs) from genera Heterorhabditis and Steinernema cause death by inducing septicimia in insect pests in the soil, moreover, endemic nearly all soils. Current study was planned to manage the oriental fruit fly, Bacterocera dorsalis (Hendel.) (Diptera: Tephritidae) hazards by using indigenous EPNs (Heterorhabditis bacteriophora, H. indica, Steinernema asiticum, S. corpocapsae and S. glasseri) as they have host finding ability and recognise as potential eco-friendly biocontrol agent over synthetic chemicals. MethodsStudy for the assessment of EPNs concentrations, various temperatures, soil type and soil moisture levels against mortality (%) of fruit fly (B. dorsalis) larvae was conducted in completely randomized design (CRD) under factorial arrangements. ResultsEPNs concentrations (70 IJs/ml, 110 IJs/ml, 150 IJs/ml) showed that S. asiaticum (150 IJs/ml) showed maximum mortality (94.97 %) of B. dorsalis as compared to other used EPNs along with their respective concentrations. Impact of various temperatures (20 °C, 24 °C, 28 °C, 32 °C, 36 °C) with respect to used EPNs exhibited that H. indica (36 °C) showed maximum mortality (94.33 %) of B. dorsalis as compared to all other treatment. Various soil types (Sandy, Sandy loam, Loam, Clay) impacted the infectivity of EPNs against fruit fly, In case of sandy loam soil, S. asiaticum showed maximum mortality (98.05 %) of B. dorsalis followed by all used treatments. Soil moisture level (12 %, 18 %, 24 %, 30 %) also significantly influenced the infectivity of EPNs against mortality of fruit fly. In case of 12% moisture level, S. asiaticum showed maximum mortality (99.06 %) of B. dorsalis over all the applied treatments along with respective moisture levels. ConclusionIn crux, Steinernema asiaticum higher concentration exhibited efficient control of fruit fly larvae in sandy loam soil with 12 % moisture level at 36 °C over the used EPN species. While application of EPNs against fruit fly is most suitable strategy to manage the fruit fly hazards and it should be included as a part of integrated pest management control programme.

Efficacy of entomopathogenic nematode isolates from Turkey against wheat stink bug, Aelia rostrata Boheman (Hemiptera: Pentatomidae) adults under laboratory conditions

BackgroundThe wheat stink bug, Aelia rostrata Boheman (Hemiptera: Pentatomidae), is one of the harmful insects that caused significant product losses in cereals due to outbreaks. Entomopathogenic nematodes (EPNs) are natural enemies of soil insect pests whose effects as a biocontrol agent against many harmful pests have been demonstrated by many laboratories and field/garden studies in the world. The present laboratory studies, using native EPNs [Steinernema carpocapsae (Black sea isolate), S. feltiae (isolate 09-31) (Aydin isolate) and Heterorhabditis bacteriophora (isolate 09-43) (Aydin isolate)] against the wheat stink bug adults, were carried out.ResultsIn the application of EPNs to the soil in plastic cups, the highest mortality rates (75 and 70%) on wheat stink bug occurred at 200 IJs cm−2 concentration of S. carpocapsae isolate at 15 and 12 °C, respectively. In other tested nematode species, the highest insect mortality was observed at 200 IJs cm−2 concentration of S. feltiae and H. bacteriophora isolates, with mortality rates of 65–35% and 55–25%, at 15 and 12 °C, respectively. S. carpocapsae (Black sea isolate) was the most pathogenic among the three nematodes tested.ConclusionsIt was concluded that S. carpocapsae had the potential as a biocontrol agent against the wheat stink bug, A. rostrata. The applications of S. carpocapsae were the great potential for the management of the pest. Effective use of EPNs should be evaluated in integrated pest management strategies between other biological control agents. According to EPNs laboratory experiments results, field trials should be conducted in future studies.

Evaluation of the entomopathogenic nematode, Steinernema asiaticum against the diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) under screen house and field conditions

BackgroundThe experiments were conducted at Research Farm, Chaudhary Charan Singh Haryana Agricultural University, Hisar, India. Infectivity and effectiveness of entomopathogenic nematode (EPN), Steinernema asiaticum infective juveniles (IJs) were evaluated against the diamondback moth (DBM), Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) as foliar spray on cabbage plants in screen house with single (30,000 IJs per plant), two (15,000 + 15,000 IJs per plant) or three (10,000 + 10,000 + 10,000 IJs per plant) applications. In the field trial, S. asiaticum (25,000 or 50,000 IJs per plant) and Malathion 50 EC (0.05%) singly or in combination at half the concentrations were used.ResultsIn screen house trial, all the treatments resulted in significantly high larval mortality than untreated plants. Split concentration application (15,000 + 15,000 IJs per plant) gave better DBM larval mortality (48.33%) compared to single application (36.00% at 30,000 IJs per plant). Comparing the two and three split applications, 15,000 IJs was significantly better (23.33% mortality) than 10,000 IJs (13.33%). In the field trial, S. asiaticum alone at 50,000 IJs resulted in 28.8% insect mortality compared to 18.0% in Malathion at 0.05%. Best results (37.5% mortality) were obtained by using nematode IJs at 25,000 per plant in combination with half the recommended concentration of Malathion (0.025%) leading to synergistic effect.ConclusionsThe study revealed that split application (15,000 + 15,000 IJs) of EPN S. asiaticum IJs proved better than single application of IJs at the same concentration (30,000 IJs) in the management of P. xylostella larvae in the screen house conditions. In the field experiment, the best effectiveness was obtained in combination of half the concentrations of EPN and insecticide (S. asiaticum IJs @ 25,000 per plant + Malathion @ 0.025%).

Combined application of entomopathogenic nematodes and fungi against fruit flies, Bactrocera zonata and B. dorsalis (Diptera: Tephritidae): laboratory cups to field study.

The peach fruit fly, Bactrocera zonata, and the Oriental fruit fly, B.dorsalis (Diptera: Tephritidae), are economically important fruit fly species in various regions of the world. We evaluated the effects of separate and combined applications of the entomopathogenic fungi (EPF) Beauveria bassiana (WG-18) and Metarhizium anisopliae (WG-02), and the entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora (VS strain) and Steinernema carpocapsae (ALL strain) against larvae, pupae and pharate adults, of B.zonata and B.dorsalis under laboratory, glasshouse and field cage conditions. Combined applications of EPF and EPNs produced greater mortality than individual treatments under all conditions. Against both species, the combination of B. bassiana and H.bacteriophora consistently exerted strong effects that were similar to the combined application of B.bassiana and S.carpocapsae whereas M.anisopliae applied with S.carpocapsae was least effective in all combinations. In a laboratory bioassay, synergistic interactions were detected between B.bassiana and H.bacteriophora applied against larvae and pharate adults of both fly species, between B.bassiana and S.carpocapsae against larvae of both species and pharate adults of B.zonata, and between M.anisopliae and H.bacteriophora against B.zonata larvae. Other combined treatments resulted in additive effects, especially against fly pupae. In a potted soil bioassay, there were only additive interactions in all combinations against different stages of both flies. The 3rd instar of both flies was more susceptible than pharate adult and pupal stages. Additive interactions between EPNs and EPF were detected in the glasshouse against 3rd instars and pupae, and under field conditions against 3rd instars of both fly species. These results indicate how particular combinations of entomopathogenic fungi and nematodes could be deployed in integrated pest management of tephritid fruit flies in orchard agro-ecosystems. © 2022 Society of Chemical Industry.

Antagonistic potential of Moroccan entomopathogenic nematodes against root-knot nematodes, Meloidogyne javanica on tomato under greenhouse conditions

The root-knot nematode, Meloidogyne javanica is a devastating pest affecting tomato production worldwide. Entomopathogenic nematodes (EPNs) are considered very promising biocontrol agents that could be used to effectively manage plant-parasitic nematode. The antagonistic activity of five EPN strains isolated from different fields in Morocco was evaluated against juvenile (J2s) antagonism in soil, the number of egg masses, and the galling index of M. javanica and J2s reproduction in the root. In greenhouse experiments, Steinernema feltiae strains (EL45 and SF-MOR9), Steinernema sp. (EL30), and those of Heterorhabditis bacteriophora (HB-MOR7 and EL27) were applied to the soil alongside RKN J2s. There was a significant reduction in M. javanica densities in the soil and roots by EPNs treatments when compared to the positive control. The EPNs decreased both egg masses formation and galling index by 80% compared to the positive control. The application of EPNs at a rate of 50 and 75 infective juveniles (IJs) cm−2 gave significant control of all studied nematological parameters compared to the positive control, which confirmed the importance of the doses applied. The applied dose was significantly correlated with M. javanica parameters according to polynomial regression models. The results also showed that S. feltiae strain (EL45) significantly increased plant height and root length, while H. bacteriophora strain (HB-MOR7) only enhanced root fresh weight. Therefore, both indigenous EPN strains; EL45 and SF-MOR9 have eco-friendly biological potential against M. javanica in vegetable crops.

Isolation, Identification, and Biocontrol Potential of Entomopathogenic Nematodes and Associated Bacteria against Virachola livia (Lepidoptera: Lycaenidae) and Ectomyelois ceratoniae (Lepidoptera: Pyralidae).

Simple SummaryFor sustainable agriculture, there is a need to identify and evaluate more biocontrol agents, including entomopathogenic nematodes (EPNs). In this study, EPNs and their associated entomopathogenic bacteria symbionts (EPBs) were isolated and identified from 320 soil samples collected in Taif, Saudi Arabia. The biocontrol efficacy of EPNs and EPBs was also evaluated against third instar larvae of the pomegranate butterfly, Virachola livia, and the carob moth, Ectomyelois ceratoniae, two important insect pests of pomegranate, under laboratory conditions. Our results show that the EPNs Steinernema spp. were more virulent than Heterorhabditis spp. against the two pomegranate insects. In addition, the EPB Stenotrophomonas maltophilia CQ1, isolated from Steinernema spp., surpassed Pseudomonas mosselii SJ10, associated with Heterorhabditis spp., in their ability to kill V. livia or E. ceratoniae larvae. We conclude that either application of EPNs’ infective juveniles (IJs) or their associated EPBs could serve as potential biocontrol agents for V. livia and E. ceratoniae.Virachola livia (Lepidoptera: Lycaenidae) and Ectomyelois ceratoniae (Lepidoptera: Pyralidae) are the key pests of pomegranates in Saudi Arabia that are managed mainly using broad-spectrum pesticides. Interactions between the entomopathogenic nematodes (EPNs) Steinernematids, and Heterorhabditids, and their entomopathogenic bacterial symbionts (EPBs) have long been considered monoxenic 2-partner associations responsible for killing insects and, therefore, are widely used in insect pest biocontrol. However, there are limited reports identifying such organisms in Taif, Saudi Arabia. The current study aimed to identify the EPNs and their associated bacteria isolated from Taif, Saudi Arabia, and evaluate their biocontrol potential on third instar larvae of V. livia and E. ceratoniae under laboratory conditions. A total of 35 EPN isolates belonging to Steinernema (20) and Heterorhabditis (15) were recovered from 320 soil samples. Twenty-six isolates of symbiotic or associated bacteria were isolated from EPNs and molecularly identified as Xenorhabdus (6 isolates), Photorhabdus (4 isolates), Pseudomonas (7), or Stenotrophomonas (9). A pathogenicity assay revealed that Steinernema spp. were more virulent than Heterorhabditis spp. against the two pomegranate insects, with LC50 values of 18.5 and 13.6 infective juveniles (IJs)/larva of V. livia for Steinernema spp. and 52 and 32.4 IJs/larva of V. livia for Heterorhabditis spp. at 48 and 72 h post-treatment, respectively. Moreover, LC50 values of 9 and 6.6 IJs/larva (Steinernema spp.) and 34.4 and 26.6 IJs/larva (Heterorhabditis spp.) were recorded for E. ceratoniae larvae at 48 and 72 h post-treatment. In addition, the EPB Stenotrophomonas maltophilia CQ1, isolated from Steinernema spp., surpassed Pseudomonas mosselii SJ10, associated with Heterorhabditis spp., in their ability to kill V. livia or E. ceratoniae larvae within 6 h post-application, resulting in 100% mortality in both insects after 24 and 48 h of exposure. We conclude that either application of EPNs’ IJs or their associated EPBs could serve as potential biocontrol agents for V. livia and E. ceratoniae.

Studies on biological control potential of Steinernema abbasi CS-39 against Helicoverpa armigera (Hub.) (Lepidoptera: Noctuidae) by adopting the regression probit model

BackgroundIn India, application of entomopathogenic nematodes (EPNs) as a bio-agent against insect pests was known since 5–6 decades with the application of the exotic species Steinernema carpocapsae (DD-136 Strain). EPNs have a strong potential to control the soil-borne insect pests. In the present study isolated strain was identified as Steinernema abbasi and docketed as CS-39. The efficacy of the isolated strain was tested against the American bollworm, Helicoverpa armigera (Hub.) (Lepidoptera: Noctuidae).ResultsLaboratory bioassay revealed that the median lethal concentration (LC50 = 83.21 IJs) of the S. abbasi isolate CS-39 was quite sufficient to achieve 100% mortality after 24 h of exposure. Mean mortality percentage was estimated > 75% at all concentrations, i.e., 25, 50, 100 and 200 IJs/larva, and 100% mortality was achieved at 200 IJs/larva after 24 h of concentration exposure. Positive relationship was found at every concentration of exposure and % mortality of the insect pest (H. armigera) after 36 (p < 0.01) and 48 h of exposure (p < 0.02).ConclusionsSteinernema abbasi isolate CS-39 found to be highly virulent to H. armigera. As the result urged, 200 IJs / larva showed 100% mortality at 36 h, whereas 100 IJs / larva showed 100% mortality at 60 h. Difference in time duration might be because of action of bacterial symbionts which were the main precursor of pathogenicity. Extensive study of secondary metabolites of the bacterial symbionts may extend the present study to the new dimension.