Strains Of Entomopathogenic Nematodes Research Articles

Entomopathogenic Nematodes Survey, Persistence in Soil, Reproductive Potential and their Effects on Meloidogyne incognita

The increasing cost of nematicides and environmental deterioration are the great challenges to agriculture. Entomopathogenic nematodes (EPNs) could be a choice as biocontrol agent in suppressing the root knot nematode, Meloidogyne incognita on tomato and other crops. A total number of 75 soil samples were collected from different locations of Vehari and Faisalabad, Pakistan. In Vehari out of 14 sites, 13 sites were found positive for EPNs, Nematodes were recovered from 19 (54 %) of 35 soil samples obtained from ecologically diverse habitats. From University of Agriculture Faisalabad, EPNs were recovered from 6 (40 %) of 15 soil samples. While, out of 25 samples collected from Ayub Agriculture Research Institute 9(36%) were found positive for EPNs. Both Steinernema and Heterorhabditis species were found in these locations. The soil samples were also analyzed to indicate the effect of soil texture. Maximum EPNs (36 %) were recovered from sandy loam soil followed by loamy soil. A series of experiments was carried out to unearth EPNs’ soil persistence, reproductive potential and their effects on root knot nematodes. All species and strains of EPNs had potential to persist in almost all type of soils. Persistence was observed in sterilized soil sand and clay (1:1). Maximum persistence was found in S. glaseri (29.11 %) followed by S. pakistanese (28.41 %), H. indica (26.93 %), S. asiaticum (24.42 %), S. feltiae (21.52 %) and H. bacteriophora (21.11 %) which showed the least persistence in sterilized soil. All species of both the families Heterorhabditidae and Steinernematidae did not persist more than 30 % in sterilized soil. Reproductive potential of three EPNs was recorded using the greater wax moth Galleria mellonella larvae. H. indica showed very high reproductive potential within wax moth followed by S. asiaticum and S. pakistanese. On the other hand, maximum emerged infective juveniles per day were recovered from H. indica followed by S. pakistanese and S. asiaticum. Suppressive effect of EPNs against root knot nematodes was observed on susceptible tomato cultivars at different concentration. S. pakistanese suppress M. incognita population more efficiently than H. indica at all the levelsi.e. 1250, 2500 and 5000 nematodes pot-1 . After 35days egg masses (EM) recovered from S. pakistanese treated pots at level 1250 were 232/pot, at level 2500 were 207 and at level 5000 were 135 respectively. Similarly, egg masses recovered from H. indica treated plants at level 1250 were 276, at level 2500 were 212 and at level 5000 were 154 EM pot-1 respectively. No EM were recovered from clean plants on contrary328 EM were recovered from plants with root knot nematodes only.

Field Control of Synanthedon myopaeformis Borkh and Zeuzera pyrina L. Using Entomopathogenic Nematodes, Insecticides and Microbial Agents

Three field trials were carried out to evaluate the efficacy of two local strains of entomopathogenic nematode, Heterorhabditis bacteriophora ( Ar-4 and Ht strains) isolated from EL-Arish and Giza in Egypt and two commercially available nematode species, Steinernema carpocapsae (All strain) and H. bacteriophora (HP88 strain) for the control of fruit tree borers, Synanthedon myopaeformis and Zeuzera pyrina on apple trees. The entomopathogenic nematodes (EPNs) were used alone or combined with recommended dose of the microbial pesticide, Bacillus thuringiensis (Diple2X), and insecticides, diazinon and phenthoate. The obtained results showed that the combined EPNs with insecticides were more effective as injection technique than spray method. Mortality percentages of S. myopaeformis ranged between 47.61 to 88.88 % in the injection treatments while in the spraying one it ranged between 37.14 to 74.07 %. In comparison between the efficacy of native and imported entomopathogenic nematodes in controlling Z. pyrina using spray technique, percentage mortality resulted from the combination of native nematodes i.e. H.bacteriophora (Ht strain) and H. bacteriophora (Ar-4 strain) and insecticides either penthoate or diazinon reached 69.23; 64.00 and 22.72; 64.18%, respectively. Whereas, percentages mortality were 44.44; 50.00 and 52.94; 54.16% with S. carpocapsae (All strain) andH. bacteriophora (HP88 strain), respectively. The susceptibility of Z. pyrina to the nematode species differed greatly according to the nematode species used either alone or in combination with the recommended dose of B. thuringiensis. The entomopathogenic nematode H. bacteriophora (HP88 strain) was more virulent than S. carpocapsae (All strain) in controlling Z. pyrina with percentage mortality reached 77.5 and 62.1%, respectively

Efficacy of two entomopathogenic nematodes strains Steinernema siamkayai and S. abbasi against the 3rd instar larvae of Chiloloba acuta

Larvae of scarabaeid beetle Chiloloba acuta (Coleoptera: Cetoninae) was found high densities in Khulekhani VDC, Makawanpur district. These insects are major pest of flower. The efficacy of two species of entomopathogenic nematodes, Steinernema siamkayai (CD1) and S. abbasi (CS1) was tested against third instar of Chiloloba acuta. In a dose response experiments, 0, 125, 250, 500, 1000, 2000 and 4000 infective juveniles (IJs) were inoculated in 50 ml plastic vial containing 40g silt loam soil (45.3% sand, 33.5% silt, 12.2% clay 4.913 organic matter and 5.5pH) and a single C. acuta larva. Mortality of C. acuta exposed to series of increase dose of two nematodes strains was analysed two days intervals upto 14th days after the inoculation by time dose mortality regression. Between these strains, S. abbasi found more effective (LD50 44.9IJs/ml) as compared to S. siamkayai (LD50 98.1IJ/ml) after 14th days. At initial days both strains had high LD50 value and it was gradually decreased with increase time.

The pathogenicity and reproduction capability of five epn strains on white grubs (Alissonotum impressicolle Arrow) in the laboratory conditions

Five entomopathogenic nematode strains, included 3 strains of the genus Steinernema, e.g. S-PQ16, SS-CP12 and S-TX1, and two strains of genus Heterorhabditis indica, e.g. H-CB3452 and H-KT3987 were evaluated on virulence and reproduction capacity on white grubs of black scarab (Alissonotum impressicolle Arrow) a serious pest damaging in the soils of sugarcane and many economic crops in Western Highland, particular Lam Dong province. The experiments were evaluated the pathogenicity virulence of EPN strains through establishing index as lethal concentration of 50 mortality percentage of host insects (LC50). While the reproduction capacity of EPN strains were established yield of infective juveniles (IJs) that produced inside insect cadavers. The bioassays on virulence of S-PQ16, S-CP12, S-TX1, H-CB3452 and H-KT3987 were revealed the mortality of white grubs as 93.3%, 86.7%; 93.3%; 86.7% and 73.3%, respectively, at the highest concentration of 5,000 IJs/insect. The 50% mortality of five indigenous strains was high levels with LC50 values ranged between 1,362 and 2,725 IJs. These values are also similar with our results previously on white grubs with some other EPN indigenous strains. It is also suitable with some evaluation bioassays of EPN on white grubs reported from China and Australia. The IJs yields from the insect cadavers were obtained up to 31×103 IJs with the strain S- CP12; 59.7×103 IJs with the S-PQ16 strain and 73.5×103 IJs with the strain S-TX1. Particularly, the highest yields were obtained from two strains of Heterorhabditis indica, viz. 125.1×103 IJs with H-KT3987 strain and 112.6×103 IJs with H-CB3452 strains. Respect to high virulence and also high reproduction capacity all these EPN strains should be satisfied the biological agents that can be used for biological control of white grubs of pests are living in the soil environment.

Characterization of Polish Steinernema silvaticum isolates (Nematoda: Steinernematidae) using morphological and molecular data.

Four strains of entomopathogenic nematodes were isolated with a live trap method in southern Poland. The isolates were identified as Steinernema silvaticum based on morphological, morphometric and molecular data. Infective juveniles of Polish S. silvaticum isolates differ in body length from S. weiseri (951 vs 740 μm, respectively), and in the hyaline tail portion from S. kraussei (48 vs 38%, respectively). First-generation males of S. silvaticum are longer than those of S. kraussei, S. weiseri and S. ichnusae (1829 vs 1400, 1180 and 1341 μm, respectively). Males of S. silvaticum and a sister species S. kraussei can be distinguished by the distance from the anterior end to the nerve ring (142 vs 105 μm), spicule (66 vs 49 μm) and gubernaculum length (45 vs 33 μm), and the presence of a mucron. The analysis of internal transcribed spacer (ITS), D2-D3 and cox1 sequences of the tested nematodes revealed differences of 3-5%, 3% and 12-13%, respectively, from S. kraussei strains. The phylogeny of both nuclear and mitochondrial genes indicated close relationships of the Polish S. silvaticum isolates with S. kraussei, S. oregonense and S. cholashanense. The reproductive isolation of the studied isolates was confirmed by hybridization tests with other European feltiae-kraussei group representatives. This study has supplemented the original description of S. silvaticum with morphological and morphometric characterization of the first-generation males and females. This is also the first molecular study of this species based on a multi-gene approach.

Evaluation of Four Entomopathogenic Nematodes as Biological Control Agents Against The Housefly, Musca domestica L. (Diptera: Muscidae)

The house fly, Musca domestica L. is considered as a notorious pest by medical, veterinary, and public health professionals worldwide. This study was carried out to evaluate the effect of different entomopathogenic nematode (EPNs) strains against the 3rd larval instar and pupal stage of the house fly. Two of them were native strains (Heterorhabditis indica and Steinernema carpocapsae) and the others were imported strains Heterorhabditis bacteriophora and Steinernema glaseri. The results indicated that the mortality of all tested stages of M. domestica were significantly influenced by the infective juveniles (IJs) concentrations and the exposure time where the maximum mortality was recorded 72 hrs. post-treatment and the larvae were more susceptible to nematodes pathogenicity than the pupae. Also, the Heterorhabditis nematodes H. baceriophora and H. indica appeared to be more effective than the Steinernema species, and H. bacteriophora (Hb88) was the most promising strain in management of both larvae and pupae causing the lower LC50 and LC95 (320.4 and 1987IJs/ml) for larvae and (1414.6 and 2664.4 IJs/ml) for pupae, respectively.

Efficacy of native entomopathogenic nematodes from Turkey against the alder leaf beetle, Agelastica alni L. (Coleoptera: Chrysomelidae), under laboratory conditions

The alder leaf beetle, Agelastica alni L. (Coleoptera: Chrysomelidae), is one of the most defoliator pests of oak and alder trees. In the present study, the efficacies of three native strains of entomopathogenic nematodes, Heterorhabditis bacteriophora (ZET35), Steinernema feltiae (ZET31), and Steinernema websteri (AS-1), were tested against pre-pupae and adults of A. alni. Experiments were conducted by four concentrations under laboratory conditions in 2015. Four different temperature regimes were tested at concentration of 1000 infective juveniles (IJs)/ml under laboratory conditions. It was observed that pre-pupae were more sensitive than adults in all tests. Based on screening tests, S. websteri was the most effective isolate on both pre-pupae and adults of A. alni at concentration of 1000 IJs/ml with 79.17 and 71.11% mortality, respectively. It caused the highest mortality values at all temperatures, except for 30 °C against pre-pupae and adults. Results of the present study suggested that S. websteri and H. bacteriophora had significant potentials against A. alni.

Isolation, Identification and Pathogenicity of Native Entomopathogenic Nematode Strains Collected from Hyderabad, Telangana State in India

Isolation, Identification and Pathogenicity of Native Entomopathogenic Nematode Strains Collected from Hyderabad, Telangana State in India

The first report of Xenorhabdus indica from Steinernema pakistanense: co-phylogenetic study suggests co-speciation between X. indica and its steinernematid nematodes.

During a survey in agricultural fields of the sub-humid region of Meerut district, India, two strains of entomopathogenic nematodes, labelled CS31 and CS32, were isolated using the Galleria baiting technique. Based on morphological and morphometric studies, and molecular data, the nematodes were identified as Steinernema pakistanense, making this finding the first report of this species from India. For the first time, we performed a molecular and biochemical characterization of the bacterial symbiont of S. pakistanense. Furthermore, a co-phylogenetic analysis of the bacteria from the monophyletic clade containing a symbiont of S. pakistanense, together with their nematode hosts, was conducted, to test the degree of nematode-bacteria co-speciation. Both isolates were also tested in a laboratory assay for pathogenicity against two major pests, Helicoverpa armigera and Spodoptera litura. The morphology of the Indian isolates corresponds mainly to the original description, with the only difference being the absence of a mucron in first-generation females and missing epiptygmata in the second generation. The sequences of bacterial recA and gyrB genes have shown that the symbiont of S. pakistanense is closely related to Xenorhabdus indica, which is associated with some other nematodes from the 'bicornutum' group. Co-phylogenetic analysis has shown a remarkable congruence between the nematode and bacterial phylogenies, suggesting that, in some lineages within the Steinernema / Xenorhabdus complex, the nematodes and bacteria have undergone co-speciation. In the virulence assay, both strains caused a 100% mortality of both tested insects after 48 h, even at the lowest doses of 25 infective juveniles per insect, suggesting that S. pakistanense could be considered for use in the biocontrol of these organisms in India.

Pathogenicity of four entomopathogenic nematode strains against Asian corn borer, Ostrinia furnacalis (Guenée), in Vietnam

Summary The virulence and reproductive capacity of four indigenous entomopathogenic nematode (EPN) strains, S-PQ16 (Steinernema sp. PQ16), S-TX1 (Steinernema sangi TX1), S-DL13 (S. siamkayai DL13) and H-NT3 (Heterorhabditis indica NT3), against the last instar larvae of Asian corn borer (ACB), was evaluated. With moderately low concentrations of infective juveniles (IJ) from 10 to 100 IJ insect−1, the ACB larvae were found to be susceptible to all four EPN nematode strains after exposure for 24, 48, 72, 96 and 120 h. The 100% mortality of ACB larvae by these indigenous EPN strains occurred after 96-120 h of exposure. The low LC50 values (between 21.7 and 27.9 IJ) indicated the high virulence of these four EPN strains to ACB larvae. The highest yield of IJ produced inside the insect cadavers for S-PQ16, S-TX1, S-DL13 and H-NT3 was 215.0 ± 6.5 × 103, 83.1 ± 4.9 × 103, 67.8 ± 7.2 × 103 and 225.2 ± 6.4 × 103 IJ, respectively, with low inoculated concentrations of between 30-50 IJ. The results, showing a high degree of virulence and high reproduction capacity, suggest that these indigenous EPN strains have great potential for biological control of the Asian corn borer.

Virulence of Native EPN Strains and their Symbionts alone to Polyphagous Lepidopteran Pests vis a vis Model Insect Galleria melonella along with in vivo Production

Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae are obligate parasites of insects and can control pests due to the symbiotic bacteria that kill the insect host by septicemia and make the environment favourable for EPNs development and reproduction. In the present paper the virulence of three Heterorhabditis sp. strains and their respective symbiotic bacteria strains alone (Photorhabdus luminescens strains) was tested under laboratory conditions against larval stages of model insect host Galleria mellonella along with two important polyphagous pests viz., Helicoverpa armigera and Spodoptera litura. The results revealed that the virulence of the three strains of Heterorhabditis sp. tested, varied considerably in terms of both LC50 as well as LT50. Feeding assays of symbiotic bacteria Photorhabdus luminescens showed that strain SG-Ngp was most effective against S. litura (LC50 = 4.06 x 105 cells/gm). It is worth mentioning that all the three strains showed lower LC50 against S. litura compared to H. armigera which concurrent with the results of IJ experiments. Among the three strains, Hms1 was found to be most efficient IJ producer, via both G. mellonella and H. armigera. Although, when H. armigera was used as the host for this strain, the yield increased by 16%. Thus, this study provides an important insight on the native EPN strains with possible insecticide potential. Besides our studies suggest that not only EPN but also its associated symbiotic bacteria alone can be used for effective pest control.

Heterorhabditis bacteriophora pampean-strain VEli (Nematoda): identification and pathogenicity against the strawberry pest Lobiopa insularis (Coleoptera: Nitidulidae)

The pampean region in the Buenos Aires province of Argentina is a major horticultural area. Biological pesticides to control pest insects available in the market are scarce in this country and nonexistent based on entomonematodes. In this paper, we characterized a native entomopathogenic nematode isolated from soil in the pampas, and evaluated its infectivity and reproductive capacity in the strawberry sap beetle Lobiopa insularis. Morphological and molecular-genetic analysis determined this isolate to be a nematode of Heterorhabditis bacteriophora, thereafter designated as the VEli strain. A 901-bp genomic-DNA fragment was isolated (GenBank Accesion No KJ575524). The new strain was pathogenic against L. insularis. In 200 ml containers with autoclaved clay soil (100 ml), at concentrations of 1,000; 5,000 and 10, 000 IJs, mortality in larvae ranged from 25 to 77 %. At a concentration of 10,000 IJs, infectivity was higher in larvae and pupae (77 ± 20% and 64 ± 25 %, respectively) than in adults (2.2 ± 1.1 %). The lethal concentration required to kill 50 and 90 % of the larvae (LC50 and LC90) over 10 days was 2,840 and 23,743 IJs. Differences were observed in the parasitism levels and emergence time of IJs between concentrations and stages, although not for production. Heterorhabditis bacteriophora strain VEli is the first entomopathogenic nematode found to infect and kill L. insularis, capable of completing its life cycle in all strawberry sap beetle stages. This availability would enable the establishment and subsequent dispersal of the strain in strawberry fields. Finally, this report constitutes the first presentation of data on the morphological, morphometric, and molecular-genetic characterization of a native entomopathogenic nematode strain from the Buenos Aires province, Argentina.

Entomopathogenic nematodes as potential biological control agents of Popillia japonica (Coleoptera, Scarabaeidae) in Piedmont Region (Italy)

AbstractIn 2014, the Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae) was first spotted in northern Italy in the Nature Park of the Ticino Valley, its first detection in continental Europe. This polyphagous invasive species has the potential to cause serious losses to horticulture and agriculture. Particularly for its management in a Nature Park, environmentally friendly strategies are necessary. To develop baseline data for a biological control approach to the Italian outbreak of P. japonica, we conducted laboratory and field experiments testing several indigenous and commercial strains of the entomopathogenic nematode (EPN) species Heterorhabditis bacteriophora and Steinernema carpocapsae against P. japonica larvae. In the laboratory, strains of H. bacteriophora caused greater mortality (ranging from 57% to 100%) than those of S. carpocapsae (3% to 77%). In micro‐plot field tests carried out at three different times, the most virulent indigenous EPN strain, H. bacteriophora ItH‐LU1, showed again the best results ranging from 44% to 93% against young larvae. Finally, in a large‐plot field trial, the commercial H. bacteriophora product provided 46% larval mortality. This study shows that H. bacteriophora strains have good potential as biological control agents of larvae of the invasive P. japonica in northern Italy.

The pathogenicity and reproduction capability of four entomopathogenic nematode strains on house cricket (Acheta domesticus) in the laboratory condition

It is first time in Vietnam the pathogenicity evaluation and reproduction capacity of four indigenous strains of entomopathogenic nematodes, viz. S-PQ16, S-QTr, H-KT3987 and H-CB3452 on house cricket (Acheta domesticus) were conducted in the labolatory condition. The lethal concentrations for the mortality 50% insect host (LC50) of S-PQ16, S-QTr, H-KT3987 and H-CB3452 strains were 99, 116, 124 and 100 IJs per one cricket, respectively. These lethal concentrations might be relative low and small LC50 values meaning that the high virulence of the epn strains to house cricket. The reproduction capacity of four epn strains in Acheta domesticus was also with high mortality in comparison with other epn strains in Vietnam and in the world. Of these two Heterorhabditis strains, e.g. H-KT3987 and H-CB3452 128.3×103 IJs and two Heterorhabditis strains with 119.6×103 IJs that were higher in comparison with their yields on Galleria mellonella and on some other insect pests. With low lethal concentration and high reproduction capacity these four epn strains to be adapted potential agents for biocontrol of house cricket. In addition, with the high reproduction capacity of epn strain house cricket can used as insect material for epn culturing in vivo in order to restore the toxic actives of the epn strains. In addition, with the available resources and cheap price, the house crickets would be used as a good alternative option for of G. mellonella in maintaining of epn strains for biocontrol of insect pests in Vietnam. Citation: Do Tuan Anh, Nguyen Ngoc Chau, 2017. The pathogenicity and reproduction capability of four entomopathogenic nematode strains on house cricket (Acheta domesticus) in the laboratory condition. Tap chi Sinh hoc, 39(1): 24-31. DOI: 10.15625/0866-7160/v39n1.8336. *Corresponding author: nguyengochau.iebr@gmail.com. Received 16 May 2016, accepted 20 March 2017

Field Monitoring and Efficacy of Entomopathogenic Nematodes Against Chamomile Stem Weevil Microplontus rugulosus and Chamomile Smooth Beetle Olibrus aeneus Under Greenhouse Conditions

Chamomile Matricaria recutita (L.) is an ancient healing plant; it is used for a sore stomach, a mild laxative, anti-inflammatory and a gentle sleep aid. Chamomile plants are infested by chamomile stem-weevil Microplontus rugulosus (Col., Curculionidae) and chamomile smooth beetle Olibrus aeneus (Col., Phalacridae), and can lead to a high reduction in chamomile yield. This work aimed to survey M. rugulosus and O. aeneus by different monitoring methods as well as to manage them by using entomopathogenic nematodes. Sweep nets, water traps, and dissecting the chamomile stems and flowers were used to monitor for M. rugulosus and O. aeneus. Chamomile insects were collected from naturally infested plants moved from the field to the greenhouse. Management of chamomile insects was conducted using three strains of entomopathogenic nematodes; while the control plants were sprayed only with water. Each strain was replicated three times and each replicate included 50 chamomile plants (combined total was 150 for each strain). Three treatment dates were carried out in May, June and July; the first one was mainly for controlling stem weevil, while the other two dates were for smooth beetle. The results showed that 70–80 % of stems had damage and symptoms of stem weevils. Thirty percents from the investigated plants were larvae free of smooth beetle; whiles 70 % was infested with different classifications (e. g. 1, 2, 3, 4 or more than 4 larvae/blooms). The results confirm that smooth beetle infestation and larval numbers were higher in May and June than July. Steinernema carpocapsae had more efficiency than S. feltiae and Heterorhabditis bacteriophora in controlling both insects. Entomopathogenic nematodes could be one of the effective management strategies to control these insects in the chamomile fields.

Acetylcholinesterases from entomopathogenic nematode Heterorhabditid bacteriophora: Susceptibility to insecticides and immunological characteristics

Acetylcholinesterases (AChEs) from the infective juveniles (IJs) of entomopathogenic nematode (EPN) have been investigated with respect to their susceptibility to insecticides and immunological characteristics, aiming at nominating the most compatible insecticide(s) to be used in conjunction with the most insecticide-tolerant EPN strain before incorporation in integrated pest management (IPM) programs. The inhibition kinetics of two purified AChE isoenzymes, AChEAII and AChEBI isolated from Heterorhabditid bacteriophora EM2 strain, by different insecticides revealed that the insensitivity to inhibition by such insecticides could be arranged in a descending order as; methomyl>carbofuran>acetamiprid>oxamyl>malathion. Except for malathion, the insecticides competitively inhibited AChEs with Ki values ranging from 0.1 to 15mM and IC50 values from 1.25 to 23mM. The two AChE isoforms are several folds less sensitive to inhibition by methomyl and carbofuran compared to those previously reported for other insect species. AChEBI was used as an immunogen to raise anti-AChEBI antisera in rabbits. The prepared antisera cross-reacted with AChEs of five different heterorhabditid nematode strains implying the presence of common epitopes shared along all the examined strains. Such studies could aid in the rational selection of the compatible insecticide(s) and the prepared polyclonal anti-AChE antisera would be a valuable immunodiagnostic tool for evaluating the most insecticide-tolerant EPN strain(s) in IPM programs.

Laboratory and field evaluation of entomopathogenic nematodes for control of Agriotes obscurus (L.) (Coleoptera: Elateridae)

AbstractThe susceptibility of the dusky wireworm, Agriotes obscurus (L.) (Coleoptera: Elateridae), to different species and strains of entomopathogenic nematodes was tested in a virulence assay in the laboratory. Larvae were exposed to different nematode doses of 50 and 100 IJs/cm2. At a dose of 50 IJs/cm2, only a commercial strain Heterorhabditis bacteriophora Poinar and the native strain Steinernema carpocapsae (Weiser) B14 caused increased mortality compared with the control (11.1% and 13.3% mortality, respectively). At the higher dose tested, all strains (except Steinernema sp. D122) were virulent to A. obscurus larvae. Steinernema carpocapsae B14 caused higher mortality of wireworm (75.6%) and was used for the assay conducted in cages, with a dose of 100 IJs/cm2, in field conditions. The results showed that S. carpocapsae B14 controlled 48.3% of A. obscurus larvae, demonstrating that some entomopathogenic nematodes have the potential to control larvae of A. obscurus. However, further work is needed to improve their efficacy.

Effects of different pesticides on virulence and mortality of some entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) have been used against especially soil borne insect pests. EPNs are feasible and attractive for biological control, because of their virulence against various insect pests, host seeking ability, being usable with standard equipment, and long-term efficacy. In addition EPNs can be applied simultaneously with some pesticides. These properties make EPNs ideal biocontrol agent in integrated pest management. In the present study, effects of 4 widely used pesticides (Glyphosate, Chlorpyrifos-ethyl, Captan, Fosetyl-al) on virulence and mortality of three EPN strains (Heterorhabditis bacteriophora Alman, H. bacteriophora HbH and Steinernema carpocapsae DD-136) were examined at 24 and 48 h periods. All strains were able to infect Galleria mellonella larvae averagely above 90 % rate, after 24 and 48 h treatments with all pesticides. However, some of the pesticides showed negative impact on the viability of the strains. Especially, DD-136 and Fosetylal seemed like incompatible, as the mortality rates were significantly higher than control for both 24 and 48 h. The results of the present study showed that it may be possible to use some EPN strains with some pesticides. It is expected that the results of the study will provide useful information for future integrated pest management programs.

Entomopathogenic nematodes for the control of the codling moth (Cydia pomonella L.) in field and laboratory trials.

Three commercially available entomopathogenic nematode (EPN) strains (Steinernema feltiae and Heterorhabditis bacteriophora Hb1 and Hb2) and two local species (S. jeffreyense and S. yirgalemense) were evaluated for the control of the codling moth (Cydia pomonella). In field spray trials, the use of S. jeffreyense resulted in the most effective control (67%), followed by H. bacteriophora (Hb1) (42%) and S. yirgalemense (41%). Laboratory bioassays using spray application in simulated field conditions indicate S. feltiae to be the most virulent (67%), followed by S. yirgalemense (58%). A laboratory comparison of the infection and penetration rate of the different strains showed that, at 14°C, all EPN strains resulted in slower codling moth mortality than they did at 25°C. After 48h, 98% mortality was recorded for all species involved. However, the washed codling moth larvae, cool-treated (at 14°C) with S. feltiae or S. yirgalemense, resulted in 100% mortality 24h later at room temperature, whereas codling moth larvae treated with the two H. bacteriophora strains resulted in 68% and 54% control, respectively. At 14°C, S. feltiae had the highest average penetration rate of 20 IJs/larva, followed by S. yirgalemense, with 14 IJs/larva. At 25°C, S. yirgalemense had the highest penetration rate, with 39 IJs/larva, followed by S. feltiae, with 9 IJs/larva. This study highlights the biocontrol potential of S. jeffreyense, as well as confirming that S. feltiae is a cold-active nematode, whereas the other three EPN isolates tested prefer warmer temperatures.

Virulence of entomopathogenic nematodes and their symbiotic bacteria against the hazelnut weevil Curculio nucum

AbstractThe virulence of different entomopathogenic nematode strains of the families Steinernematidae and Heterorhabditidae, isolates from Catalonia (NE Iberian Peninsula), and their symbiotic bacteria was assessed with regard to the larvae and adults of the hazelnut weevil, Curculio nucum L. (Coleoptera: Curculionidae). The nematode strains screened included one Steinernema affine, five Steinernema feltiae, one Steinernema carpocapsae, one Steinernema sp. (a new species not yet described) and one Heterorhabditis bacteriophora. The pathogenicity of all the strains of nematodes was tested on larvae and only four of them on adults of the hazelnut weevil. Larval mortality ranged from 10% with S. affine to 79% with Steinernema sp. Adult mortality was higher in S. carpocapsae, achieving 100% adult weevil mortality. The pathogenicity of the symbiotic bacteria Xenorhabdus bovienii, X. kozodoii, X. nematophila and Photorhabdus luminescens was studied in larvae and adults of C. nucum. In the larvae, X. kozodoii showed a LT50 of 22.7 h, and in the adults, it was 20.5 h. All nematodes species except S. affine tested against larvae showed great potential to control the insect, whereas S. carpocapsae was the most effective for controlling adults.