Use of entomopathogenic fungi combined with biorational insecticides to control Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) under semi-field conditions

Grasshoppers are among the invertebrate herbivores that cause most economic losses in grasslands throughout Argentina’s Pampas and parts of Patagonia. Chemical insecticides remain the sole option for grasshopper control in this area, despite being of significant environmental concern. Our aim was to evaluate the efficacy of combinations between three entomopathogenic fungi strains (Beauveria bassiana LPSc 1067 and LPSc1082), and Metarhizium anisopliae (LPSc 907), two biorational insecticides (luphenuron and methoxyfenozide), and a new synthetic chemical pesticide (rynaxypyr) in the control of the pest grasshopper Dichroplus maculipennis under field cage conditions. Fungal strains used were adjusted to 1 × 10⁸, 1 × 10⁶ and 1 × 10⁴ conidia/ml. Insecticides were tested at three concentrations: the average concentration recommended for application in the field (100%), 50% of that level and finally 25%. Combinations of the insecticides with B. bassiana (LPSc 1067, LPSc 1082) and M. anisopliae (LPSc 907) caused higher mortality to D. maculipennis nymphs than any of the individual agents used alone. The three insecticides tested did not negatively affect the isolates of the two species of entomopathogenic fungi employed.     

Effects of Metarhizium anisopliae on Meccus pallidipennis (Hemiptera: Reduviidae) over different types of wall surfaces

The entomopathogenic fungus Metarhizium anisopliae is virulent for the insect triatomine Meccus pallidipennis. To evaluate the functionality of a fungal formulation (vegetable oil and emulsifiers) of this fungus, virulence was assayed by insect mortality on the pronotum of third instar nymphs (N3) M. pallidipennis in laboratory conditions and ST₅₀ was calculated. Mortality was evaluated directly: 100%, 97.33% and 98.66% mortalities were caused by formulation, emulsified formulation and fungal conidia, respectively, at day 8 of insect infection. Another bioassay was carried out in simulated external conditions (peridomicility) using red and gray brick walls, a stone fence and mountain soil (experimental units). These simulated conditions were infected with 10?ml of a 1?×?10⁹?conidia/ml emulsified formulation by means of a manual sprinkler prior to the placement of the nymphs. Ten N3 M. pallidipennis were deposited in each experimental unit and insect mortality was monitored every 12?h for 22 days. Each treatment was replicated four times. With the red brick wall, a mortality of 90% at day 22 and a ST₅₀ of 15 days were obtained on N3 M. pallidipennis; with the gray brick wall, 100% mortality and a ST₅₀ of 13 days; and with the stone fence, 88.33% mortality and a ST₅₀ of 21 days. The results obtained in this research work indicate that the formulation with conidia of the M. anisopliae strain EH-473/4 may be auxiliary in the development of strategies for the control of Chagas disease insect transmitters such as M. pallidipennis.     

Pine processionary moth (Thaumetopoea pityocampa,Lepidoptera: Thaumetopoeidae) larvae are highly susceptible to the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana

The larvae of the pine processionary moth (PPM), Thaumetopoea pityocampa, feed on the needles of pine and cedar. The urticating hairs of older instars pose a threat to human and animal health. Strains of the entomopathogenic fungi, Metarhizium brunneum (V275, ARSEF 4556) and Beauveria bassiana (KTU-24), were assayed against first to fourth instar T. pityocampa using doses ranging from 1?×?10⁵ to 1?×?10⁸ conidia mL^?1. The three strains differed slightly in their virulence but caused 100% mortality of all instars at the highest dose. The newly emerged or first instar larvae were extremely susceptible with 100% mortality being achieved 2–4 days post inoculation with V275 at all but the lowest dose. The fourth instar larvae appeared to be less susceptible than earlier instars. There was good horizontal transmission of conidia from treated to un-inoculated larvae. However, mortality was higher in third and fourth instars and where the ratio of inoculated versus untreated larvae was high. This we presume is due to spores being more readily trapped by the urticating hairs found on third and older instar larvae. Injection of the nests offers a simple and environmentally friendly way of controlling the pest with reduced risk to operators.     

Effects of four commercial fungal formulations on mortality and sporulation in house flies (Musca domestica) and stable flies (Stomoxys calcitrans)

The house fly Musca domestica L. (Diptera: Muscidae) and stable fly Stomoxys calcitrans (L.) (Diptera: Muscidae) are major pests of livestock. Biological control is an important tool in an integrated control framework. Increased mortality in filth flies has been documented with entomopathogenic fungi, several strains of which are commercially available. Three strains of Beauveria bassiana (Balsamo‐Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) and one strain of Metarhizium brunneum (Petch) (Hypocreales: Clavicipitaceae) were tested in commercial formulations for pathogenicity against house flies and stable flies. There was a significant increase in mortality of house flies with three of the formulations, BotaniGard^® ES, Mycotrol^® O, and Met52^® EC, during days 4–9 in comparison with balEnce? and the control. In stable flies, mortality rates were highest with Met52^® EC, followed by Mycotrol^® O, BotaniGard^® ES and, finally, balEnce?. There was a significant fungal effect on sporulation in both house flies and stable flies. Product formulation, species differences and fungal strains may be responsible for some of the differences observed. Future testing in field situations is necessary. These commercial biopesticides may represent important tools in integrated fly management programmes.     

Efficacy of entomopathogenic nematodes against neonate larvae of <Emphasis Type="Italic">Capnodis tenebrionis</Emphasis> (L.) (Coleoptera: Buprestidae) in laboratory trials

The efficacy of five entomopathogenic nematode strains of the families Steinernematidae and Heterorhabditidae was tested against the neonate larvae of Capnodis tenebrionis. The nematode strains screened included two of Steinernema carpocapsae (Exhibit and M137), and one each of S. feltiae (S6), S. arenarium (S2), and Heterorhanditis bacteriophora (P4). Exposure of neonate larvae of Capnodis to 10 and 150 infective juveniles (IJs) per larva (equivalent to 3 and 48 IJs/cm² respectively) in test tubes with sterile sand, resulted in mortality between 60–91% and 96–100%, respectively. At a concentration of 150 IJs/larva, all of the nematode strains were highly virulent. Both S. carpocapsae strains (Exhibit and M137) caused infection and mortality to larvae more quickly than the other strains. However, at a lower concentration assay (10 IJs/larva), S. arenarium was the most virulent strain. The penetration rate as an indicator of entomopathogenic nematode infection was also evaluated. The highest value was recorded for S. arenarium (36%), followed by H. bacteriophora (30.6%), S. feltiae (23.1%), and S. carpocapsae (20.7%).     

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

The 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.     

Entomopathogenic fungi from Argentina for the control of Schistocerca cancellata (Orthoptera: Acrididae) nymphs: fungal pathogenicity and enzyme activity

The South American locust Schistocerca cancellata (Serville) was the most serious agricultural pest in Argentina during the first half of the last century and remains as a threat when preventive control measures are relaxed in the outbreak area. In this study, we analysed in the laboratory, the effectiveness of 26 fungal strains (isolated from both insects and soil collected in Argentina) for S. cancellata control and determined the relationship between the chitinase, protease and lipase levels in these fungi and their insecticidal activities. We observed that Beauveria bassiana (isolate LPSC 1067) caused the highest mortality (90±1.03%), the highest values of chitinolytic, proteolytic and lipolytic activity were 6.13±0.05, 2.56±0.11 and 2.33±0.47, respectively, and the lowest median lethal time was 5.96 days. This is the first time that a wide variability in chitinase, protease and lipase activity as well as in virulence has been reported in a representative sample of different entomopathogenic fungal strains from Argentina.     

Investigations on the efficacy of entomopathogenic nematodes against Spodoptera littoralis (Biosd.) and Galleria mellonella (L.)

Abstract

The infectivity of seven entomopathogenic nematode strains of the families Steinernematidae and Heterorhabditidae were tested against the last instar larvae of the cotton leafworm, Spodoptera littoralis (Biosd.) and the greater wax moth, Galleria mellonella (L.) in a Petri dish and sand column assay. Exposure of the insect species was done at a dose of 100 IJ/ ml. Heterorhabditis sp. ELG., H. indica, Heterorhabditis sp. ELB. were the highest in activity, they gave a 100% mortality to S. littoralis larvae in a Petri dish assay 24 h postexposure. The rest of the strains tested gave mortalities ranged between 50 and 90% at 24 h then 100% after 48 h postexposure . In the sand-column assay strains, Heterorhabditis sp. ELB., S. riobravae and S. carpocapsae were the highest in activity against S. littoralis with 100% mortality within 24 h postexposure. The results of infectivity against G. mellonella showed that H. indica was the highest in the Petri dish assay and H. egyptii was the highest in the sand column assay with 100% mortality after 24 h of exposure. The penetration rate as an indicator of entomopathogenic nematode infection was also evaluated. The highest value was recorded for Heterorhabditis sp. ELB. (62.3%) and S. carpocapsae (61.4%) against S. littoralis in both the Petri dish and sand-column assay, respectively. In the case of G. mellonella, the highest value of penetration was recorded for Heterorhabditis sp. ELG. (68.3%) and S. riobravae (65.00%) in both the Petri dish and sand-column assay, respectively.     

Brevibacterium frigoritolerans a novel entomopathogen of Anomala dimidiata and Holotrichia longipennis (Scarabaeidae: Coleoptera)

We describe the isolation, biochemical characterization, phylogenetic analysis, and pathogenecity of a novel entomopathogenic bacterium Brevibacterium frigoritolerans to first instar larvae of Anomala dimidiata and Holotrichia longipennis. The almost full length 16S rRNA sequence of the bacterium has 99% identity with the type strain of B. frigoritolerans, while phylogenetic analysis revealed that the isolate formed a tightly linked branch with the type strain of B. frigoritolerans. Under in vitro bioassay conditions, the isolate infected and caused 89±5.4 and 74±7.7% mortality, in first instar larvae of A. dimidiata and H. longipennis, respectively. The infected larvae exhibited bacteremia like symptoms and mortality occurred between the second and fifth weeks after inoculation. This is an early report on the entomopathogenic potential of the hitherto lesser-known bacterium Brevibacterium frigoritolerans.     

Insect-associated fungi from naturally mycosed vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Vine mealybug, Planococcus ficus, is a major pest of grapevine, which is present in at least 39 countries. According to American Vineyard Foundation, P. ficus is in the top ranks among major insect-pests of grapevine. It is the ‘top priority concerns’ by grape growers and a ‘threat to the sustainability of wine industry’ demanding a ‘high priority research’. In Douro vineyards, it is considered as an occasional insect-pest; however, its importance is increasing in some localities. The present study investigates the occurrences of P. ficus-associated fungi. Vine mealybugs were observed in two of the four surveyed farms. Out of the 183 collected mealybugs, 58 were dead of which 25 had symptoms of mycosis and 13 were parasitised. Subculturing cadavers and subsequent pathogenicity test yielded 22 entomopathogenic fungi (EPF) including yeasts. The yeast Meyerozyma (=Pichia) guilliermondii, and the EPF Sarocladium kiliense and Purpureocillium lilacinum were the most abundant, i.e. representing 18.18% (N?=?4), 13.64% (N?=?3) and 13.64% (N?=?3) of the isolates, respectively. Considering biological affinities, fungal families Nectriaceae and Microascaceae had the most similar count-data profiles. To our knowledge, this work reports the first isolations of EPF from vine mealybug worldwide; and Pseudocosmospora rogersonii in Europe and as EPF worldwide. The mortality rate originated by mycoses on P. ficus was significantly higher than by its parasitoids, suggesting that fungi as P. ficus biocontrol agents are relatively more important than considered before. Overall, this report provides new insights into the development of mycoinsecticides and conservation biocontrol strategies for P. ficus pest management.     

The role of the different fermentation media and infection processes on the infectivity of the bacterial symbionts to Spodoptera littoralis (biosduval) (Lipedoptera: Noctuidae)

Abstract

Bacterial symbionts are one of the most toxic bacteria to insect pests. They have been isolated from the intestine of the entomopathogenic nematodes. Ten strains of the entomopathogenic nematodes, that may be different, have been isolated out of different soil fauna having different crops from different Governorates in Egypt. The bacterial symbionts in these strains have been isolated and tested for production parameters using four different media. Experiments showed that both Loria Broth (LB), and Nutrient Broth (NB) gave good results in laboratory production of bacterial symbionts, concerning stability, cell size, and pigment production during culturing. Experiments using different techniques of introducing the bacterial symbionts to larvae of the cotton leafworm showed that the injection technique was the most effective among all the tested techniques. This is followed by oral and forced feeding which seemed to give equal results. On the other hand, toxicity experiments showed that the four bacterial isolates named, G-NRC-A₃, SH-NRC-A₅, SH-NRC-A₆, and N.Sinai-NRC-A₈, besides the bacterial symbiont of Steinernema abbasi, Flavimonas oryzihabitans, all give 100% mortalities to Spodoptera littoralis larvae after 24 h post-treatment at the higher dose (5×10⁴ cells/10 μl) but at the lower doses 5×10³ and 5×10² cells/10 μl of injection solution, a 100% mortality was reached after 72 h post-treatment.     

Entomopathogenic fungi of Eurygaster integriceps Puton (Hemiptera: Scutelleridae): collection and characterization for development

Exploratory activities were done in Syria, Turkey, Iran, Uzbekistan, Kazakhstan, The Kyrghyz Republic, and Russia to locate entomopathogenic fungi of Eurygaster integriceps. Isolates from the entomopathogenic genera Beauveria, Paecilomyces, and Verticillium were collected. Beauveria bassiana was the most commonly recovered species. Thirty-one isolates of the 221 recovered were examined at 20, 25, 30, and 35 °C for 20 days for growth and sporulation. Growth and sporulation were generally highest at 25 °C. None of the isolates grew at 35 °C, and at 30 °C growth was retarded with no conidia being produced. Single- and multiple-concentration bioassays were conducted on greenhouse-grown wheat plants and in pine litter to evaluate virulence of fungi from several sources to E. integriceps. When tested at a single concentration, mortality after 15 days ranged from 66 to >95% in the litter assays and 50 to 91% in the plant assays. There was a distinct concentration response for most of the isolates tested in the multiple-concentration assay, particularly in the in-litter environment. In litter, mortality tended to develop earlier than in on-plant assays. Several isolates of B. bassiana and one Metarhizium anisopliae displayed consistently high virulence against E. integriceps and were more virulent than two commercial strains. Our results demonstrate the potential of entomopathogenic fungi for management of E. integriceps in overwintering sites and in wheat fields.     

Entomopathogenic fungi disturbed the larval growth and feeding performance of Ocinara varians (Lepidoptera: Bombycidae) larvae

Abstract Feeding experiments using three strains of entomopathogenic fungi, Beauveria bassiana, Metarhizium anisopliae and Isaria fumosorosea were conducted with newly moulted 3rd–5th instar Ocinara varians Walker larvae in the laboratory. The mortality of larvae immersed individually in spore suspension (1 × 10⁷ spores/mL) of all the strains was ≥ 80% except 5th instar larvae treated with M. anisopliae which transformed into pupae, but did not result in adult emergence. The growth (total body mass), consumption, relative consumption rate and relative growth rate, were reduced at all three larval stages, while developmental time was extended in infected larvae with concurrent significant increase in approximate digestibility in infected larvae. Conversion of digested food (ECD) and ingested food (ECI) values declined in infected larvae as compared to the healthy larvae (control). The 5th instar larvae treated with M. anisopliae showed higher ECD and ECI values than control. Based on mortality and growth inhibition it can be suggested that all the studied fungal strains have a high potential for biocontrol and could be developed into biocontrol agents against O. varians.     

Evaluating mulches together with Heterorhabditis zealandica (Rhabditida: Heterorhabditidae) for the control of diapausing codling moth larvae,Cydia pomonella (L.) (Lepidoptera: Tortricidae)

The potential of using an entomopathogenic nematode, Heterorhabditis zealandica Poinar, together with different test mulches (pine chips, wheat straw, pine wood shavings, blackwood and apple wood chips) to control diapausing codling moth, Cydia pomonella (L.) larvae was evaluated. Mesh cages were identified as a suitable larval-containment method. High levels of codling moth mortality were obtained when using pine wood shavings as mulch (88%) compared to pine chips, wheat straw, blackwood and apple wood chips (41–88%). Humidity (>95% RH) has to be maintained for at least 3 days to ensure nematode survival. It was also proven that nematodes had the ability to move out of infected soil into moist mulch, to infect the codling moth larvae residing at heights of up to 10 cm. Field experiments showed the importance of climatic conditions on nematode performance. Low temperatures (<15°C) recorded during the first trial resulted in low levels of control (48%), as opposed to the 67% mortality recorded during the second trial (temperatures ranged between 20 and 25°C). Low levels of persistence (<10%) were recorded in the mulches post-application. The study conclusively illustrated some of the baseline requirements fundamental to the success of entomopathogenic nematodes together with mulches for the control of codling moth.     

Natural mortality of immature stages of Bactrocera oleae (Diptera: Tephritidae) in traditional olive groves from north-eastern Portugal

From 2006 to 2008, we studied the natural mortality of olive fly, Bactrocera oleae (Rossi), eggs and larvae as collected in fruit on the tree, in two to five ‘traditional’ olive groves of Trás-os-Montes (north-eastern Portugal), per year. We also studied the fate of 2044 puparia that were buried in the soil from November to May for two seasons, by using exclusion cages to estimate predation. Mortality of eggs inside the fruit was estimated as between 5.4±2.4 and 16.6±6.1%, and as 10.7±2.1 and 100.0% for young larvae. Similarly, the estimated mortality of mature larvae was between 0 and 66.7±33.3%. The highest mortality levels for young larvae could reach 100% during August, and 47.4% during the first fortnight of December, coincident with high temperatures in summer or low temperatures at the end of autumn and early winter. Mortality (winter disappearance) of puparia was estimated at up to 98.5% of the population. Predation of eggs was low, at 0.6±0.3 to 6.3±4.0% in 2006, 0 to 4.1±1.1% in 2007, and 0 to 3.6±3.6% in 2008. Parasitism was insignificant during the study, and only one parasitoid was identified, the eulophid Pnigalio agraules (Walker). We also surveyed entomopathogenic fungi associated with the insect in 12 olive groves, and evaluated three of the latter against larvae, puparia, and adult B. oleae in the laboratory. Of the 15 fungal species identified from immature stages, three were considered to be entomopathogenic (i.e. Cordyceps bassiana, Penicillium corylophilum and Mucor hiemalis). We observed up to 20.0±3.2% and 94.0±2.5% mortality of larvae and puparia, respectively when treated with P. corylophilum and up to 32.5±11.1% of adults when treated with M. hiemalis.     

Effect of entomopathogenic fungi upon adults of Stomoxys calcitrans and Musca domestica (Diptera: Muscidae)

The pathogenicity and virulence of 10 isolates of entomopathogenic fungi from the soil of lodging pens of dairy production units in Aguascalientes, Mexico, on adults of Stomoxys calcitrans and Musca domestica were determined. All isolates were pathogenic when exposed by aspersion to a concentration of 1×10⁸ conidia/ml, causing between 20.3 and 91.7% mortality in S. calcitrans and between 31 and 91.7% in M. domestica at 7 days post-exposure; in S. calcitrans isolates of Beauveria bassiana (Bb114) and Metarhizium anisopliae (Ma135), sensu lato, were the most noteworthy as mortality reached above 90% with an LC₅₀ of 3.5×10⁵ conidia/ml for Bb114, while for Ma135 reached 1.6×10⁴ conidia/ml. In M. domestica Ma134 and Ma135 showed mortality above 90% with an LC₅₀ of 4.3×10⁴ and 1.4×10⁵ conidia/ml, respectively.     

Efficacy of entomopathogenic nematodes against potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae) under laboratory conditions

The susceptibility of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) to native and commercial strains of entomopathogenic nematodes (EPNs) was studied under laboratory conditions. Native strains of EPNs were collected from northeastern Iran and characterised as Steinernema feltiae and Heterorhabditis bacteriophora (FUM 7) using classic methods as well as analysis of internal transcribed spacer (ITS) and D2/D3 sequences of 28S genes. Plate assays were performed to evaluate the efficiency of five EPN strains belonging to four species including Steinernema carpocapsae (commercial strain), S. feltiae, Steinernem glaseri and H. bacteriophora (FUM 7 and commercial strains). This initial assessment with 0, 75, 150, 250, 375 and 500 IJs/ml concentrations showed that S. carpocapsae and H. bacteriophora caused the highest mortality in both larval and prepupal stages of P. operculella, PTM. Thereafter, these three strains (i.e. S. carpocapsae, H. bacteriophora FUM 7 and the commercial strains) were selected for complementary assays to determine the effects of soil type (loamy, loamy–sandy and sandy) on the virulence of EPNs against the second (L2) and fourth instar (L4) larvae as well as prepupa. A soil column assay was conducted using 500 and 2000 IJs in 2-ml distilled water. Mortality in the L2 larvae was not affected by the EPN strain or soil type, while there was a significant interactive effect of nematode strains and soil type on larval mortality. The results also showed that EPN strains have higher efficiency in lighter soils and caused higher mortality on early larvae than that in loamy soil. In L4 larvae, mortality of PTM was significantly influenced by nematode strain and applied concentrations of infective juveniles. The larval mortality induced by S. carpocapsae was higher than those caused either by a commercial or the FUM 7 strain of H. bacteriophora. Prepupa were the most susceptible stage.     

Isolation and evaluation of South African isolates of Beauveria bassiana (Hypocreales: Cordycipitaceae) on Rhipicephalus microplus (Acari: Ixodidae)

Beauveria bassiana (Hypocreales: Cordycipitaceae) is an entomopathogenic fungus that has shown promising results as a biocontrol agent of ticks. Locally isolated B. bassiana are better acclimatised to the natural conditions of their geographical origin; therefore, they are essential in developing effective biocontrol agents for ticks. The current study aimed to isolate native strains of B. bassiana that are pathogenic to Rhipicephalus microplus ticks. The virulence of the isolates was tested against R. microplus larvae using a formulation containing 15% avocado oil, 0.05% adjuvant and 10⁸ conidia mL^?1. The two best strains were further evaluated for various biological parameters on adult engorged female ticks. Breakthru® or Ballista® (adjuvant) was mixed with the formulation to compare their effect on the isolates' virulence. In total 61 entomopathogenic fungi were isolated from the 360 greater wax moth larvae, Galleria mellonella (Lepidoptera: Pyralidae) used. The virulence test identified Bb-40 and Bb-41 to be the most virulent isolates against R. microplus larvae with mortalities of 91 and 93% and LT₅₀ values of 5.8 and 6.2 days, respectively. Compared to the control, both strains significantly affected all the measured biological parameters. The type of adjuvant also considerably affected the susceptibility of ticks to the fungi. In conclusion, the two isolates combined with adjuvants can be used as a biocontrol agent to control R. microplus.

     

Entomopathogenic nematodes from north-eastern South Africa and their virulence against false codling moth,Thaumatotibia leucotreta (Lepidoptera: Tortricidae)

A survey was undertaken to determine the diversity and frequency of endemic entomopathogenic nematodes (EPN) in subtropical regions in the Mpumalanga, Limpopo and KwaZulu-Natal provinces of South Africa. A total of 136 soil samples were randomly taken from cultivated and uncultivated habitats, including subtropical fruit tree orchards (avocado, litchi, macadamia, mango and guava) and adjoining natural vegetation. EPNs were isolated from 14 samples (10.3%) by means of baiting with Tenebrio molitor larvae. Heterorhabditis was the most common genus isolated from 12 samples, whereas only two Steinernema species were isolated. The most common Heterorhabditis isolated were Heterorhabditis noenieputensis and H. zealandica, which were both isolated from four samples each. The present report is the first occurrence of H. taysearae and H. baujardi in South Africa. The two Steinernema species are both unknown species. Laboratory bioassays were conducted to determine the potential of seven native EPN isolates to control the false codling moth (Thaumatotibia leucotreta) (FCM). Last instar FCM larvae were found to be most susceptible to S. yirgalemense (157-C), H. zealandica (WS 23) and Steinernema litchii (WS9), when exposed to 50 IJs/50?µ? water for 48?h, causing 100%, 94.2% and 93.5% mortality, respectively.     

Pathogenicity of Heterorhabditis nematodes isolated from north-western Himalaya against the larvae of Plutella xylostella (L.) (Lepidoptera: Plutellidae)

The efficacy of three entomopathogenic nematodes (Heterorhabditis spp.), from north western Himalaya, India was studied against the diamondback moth, Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), under laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the dosages of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also evaluated against the commercially available entomopathogenic nematode H. indica. An indigenous isolate, H. bacteriophora (HRJ), along with the commercial isolate H. indica recorded 100.0% mortality of insect larvae in 96 h exposure time against third instar larvae of P. xylostella. However, it was noticed that with the advancement of larval stage its mortality rate reduces and vice versa with the exposure period. All the tested nematode species were also found to reproduce within the host and produced infective juveniles. In conclusion, the evidence obtained in this study suggests that all the three indigenous EPN species are virulent enough to produce 100% mortality of larvae of P. xylostella. These EPN species thus have potential for the management of P. xylostella under integrated management practices.