Susceptibility of shore fly <Emphasis Type="Italic">Scatella stagnalis</Emphasis> to five entomopathogenic nematode strains in bioassays

The shore fly, Scatella stagnalis (Fallén) (Diptera: Ephydridae) is an important insect pest of greenhouse crops. We evaluated two different Spanish isolates of entomopathogenic nematodes, Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) and Steinernema arenarium (Artyukhovsky) (Rhabditida: Steinernematidae), and two commercially available strains, Steinernema feltiae (Nemaplus^®) and Heterorhabditis bacteriophora (Poinar) (Rhabditida: Heterorhabditidae) (Nematop^®) against shore flies. In tests conducted in 24-well plate filter paper applied at 5, 11, 22, 44 and 88 nematodes per larva, all nematodes produced significant shore fly larval mortality. The lowest concentration tested was enough to obtain high larval mortality (65.2–87.0%). The nematodes Steinernema feltiae and Steinernema arenarium, which parasitized the shore fly larvae faster, also penetrated in higher number in the shore fly larva (4.6–8.8% penetration rate). In bioassays conducted in algae, Steinernema feltiae, applied at 50 nematodes/cm², caused highest (100%) and Steinernema arenarium lowest shore fly mortality (94%). Our results suggest that entomopathogenic nematodes appear feasible for controlling shore flies but further tests are needed to determine their efficacy in the field.     

Immune defenses of <Emphasis Type="Italic">Agriotes lineatus</Emphasis> larvae against entomopathogenic nematodes

The present work describes the immune response of wireworm larvae, Agriotes lineatus (L.) (Coleoptera: Elateridae) when challenged with two species of entomopathogenic nematodes, Steinernema feltiae (Filipjev) (Strongyloidea: Steinernematidae) and Heterorhabditis bacteriophora (Poinar) (Rhabiditoidea: Heterorhabditidae). Two main immunological processes including cellular and humoral reactions have been addressed. Total haemocyte counts after infection with H. bacteriophora increased quickly in initial times, but decreased over time post-injection (at 12 and 16 h). Instead, haemocyte numbers after infection with S. feltiae was unchanged in the early stage, but significantly decreased until 16 h post-injection. Plasmatocytes and granulocytes showed more significant changes compared to other haemocytes. The encapsulation response to parasites was significantly different against two nematode species. Particularly, S. feltiae was almost unrecognized by host haemocytes (5.85 % of encapsulated parasites). Assays with H. bacteriophora showed 23.5 % of encapsulated nematodes. From 8 to 12 h after H. bacteriophora infection, an increase in phenoloxidase activity was detected, while in the larvae injected with S. feltiae the enzymatic activity decreased gradually reaching the lowest level 16 h post-injection. This is the first report on the modulation of immune response of wireworm larvae after infection with entomopathogenic nematodes.     

Comparison of the methods applicable for the pathogenicity assessment of entomopathogenic nematodes

Single infective juveniles of Heterorhabditis bacteriophora, H. megidis (Nematoda: Heterorhabditidae), Steinernema arenarium, S. carpocapsae and S. feltiae (Nematoda: Steinernematidae) were used to infect single Galleria mellonella (Lepidoptera: Pyralidae) larvae. Four parameters of entomopathogenic nematodes pathogenicity were assessed: the mortality of insects, infectivity of nematodes, number of nematodes established per single G. mellonella, and degree of infective juveniles colonization (percent of infective juveniles which intestine was colonized by symbiotic bacteria). The accuracy, repeatability, and versatility for different species of EPNs in bioassay arenas were compared. Our modifications of the original methods yielded ~ 50% higher efficiency of infective juveniles in cell culture plates and > 20% higher efficiency in centrifuge test tubes. The efficiency of nematodes in cell culture plates (39–77%) was relatively low, especially in the case of Heterorhabditis spp. In the bioassay arena, infective juveniles migrated between cells. The results of our studies indicate that the pathogenicity of EPNs should be assessed in centrifuge test tubes. In these arenas, the infectivity of single IJs was ~ 90% for Heterorhabditis spp. and ~ 95% for Steinernema spp. The degree of colonization of the EPN isolates by symbiotic bacteria was in the range of 96–98%.     

Compatibility between Forficula auricularia and entomopathogenic nematodes to be used in pome fruit pest management

Use of predators, parasitoids and entomopathogens as biocontrol agents in pome fruit production can lead to more efficient and sustainable pest management programmes. The European earwig (Forficula auricularia Linnaeus [Dermaptera: Forficulidae]) is a major predator of key pests in pome fruit orchards, and entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae are obligate parasites of a large number of insect species. Therefore, the interaction between earwigs and EPNs can play an important role in pest management programmes. Susceptibility of the European earwig to Steinernema carpocapsae, Steinernema feltiae (Steinernematidae) and Heterorhabditis bacteriophora (Heterorhabditidae) was evaluated. S. carpocapsae was the only tested EPN capable of killing the European earwig. However, the European earwig can detect the presence of S. carpocapsae and therefore avoid nematode‐treated shelters. An earwig deterrent activity in EPN‐killed codling moth larvae that reduces the foraging of European earwig on insect cadavers containing nematodes and allows nematodes to complete their life cycle was also assessed with the three species of nematodes. These findings suggest a positive compatibility between the European earwig and EPNs.     

Biocontrol potential of the entomopathogenic nematodes Heterorhabditis bacteriophora and Steinernema carpocapsae on cucurbit fly,Dacus ciliatus (Diptera: Tephritidae)

Entomopathogenic nematodes (EPNs) from the families Steinernematidae and Hererorhabditidae are considered excellent biological control agents against many insects that damage the roots of crops. In a regional survey, native EPNs were isolated, and laboratory and greenhouse experiments were conducted to determine the infectivity of EPNs against the cucurbit fly, Dacus ciliatus Loew (Diptera: Tephritidae). Preliminary experiments showed high virulence by a native strain of Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) and a commercial strain of Steinernema carpocapsae Weiser (Rhabditida: Steinernematidae). These two strains were employed for further analysis while another native species, Steinernema feltiae, was excluded due to low virulence. In laboratory experiments, larvae and adult flies were susceptible to nematode infection, but both nematode species induced low mortality on pupae. S. carpocapsae had a significantly lower LC₅₀ value against larvae than H. bacteriophora in filter paper assays. Both species of EPNs were effective against adult flies but S. carpocapsae caused higher adult mortality. When EPN species were applied to naturally infested fruit (150 and 300 IJs/cm²), the mortality rates of D. ciliatus larvae were 28% for S. carpocapsae and 12% for H. bacteriophora. Both EPN strains successfully reproduced and emerged from larvae of D. ciliates. In a greenhouse experiment, H. bacteriophora and S. carpocapsae had similar effects on fly larvae. Higher rates of larval mortality were observed in sandy loam and sand soils than in clay loam. The efficacy of S. carpocapsae and H. bacteriophora was higher at 25 and 30°C than at 19°C. The results indicated that S. carpocapsae had the best potential as a biocontrol agent of D. ciliatus, based on its higher virulence and better ability to locate the fly larvae within infected fruits.     

Impact of multiple natural enemies on immature <Emphasis Type="Italic">Drosophila suzukii</Emphasis> in strawberries and blueberries

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) oviposits in ripening fruit, larvae render crops unmarketable, and significant economic losses can occur. Biological control research has focused on individual natural enemy species against immature D. suzukii. Here we combine two predators and an entomopathogenic nematode, expecting species complementarity and increased control of D. suzukii. In strawberries, Orius insidiosus (Say) (Hemiptera: Anthocoridae) plus Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) resulted in fewest D. suzukii (81% reduction), and in blueberries, results were similar (60% reduction), although H. bacteriophora was not as effective as in strawberries, which was likely due to drier substrate conditions. There was neither strong complementarity nor interference between predators, O. insidiosus and Dalotia coriaria Kraatz (Coleoptera: Staphylinidae). Inclusion of O. insidiosus resulted in 50% fewer D. suzukii than combinations without O. insidiosus. Control of D. suzukii can be improved with multiple natural enemies, and combinations of O. insidiosus with other agents (parasitoids, fungal entomopathogens) should be tested.     

Evaluation of the efficacy of <Emphasis Type="Italic">Steinernema carpocapsae</Emphasis> in a chitosan formulation against the red palm weevil, <Emphasis Type="Italic">Rhynchophorus ferrugineus</Emphasis>, in <Emphasis Type="Italic">Phoenix canariensis</Emphasis>

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera, Curculionidae), is an important pest of palms. It has recently colonized the Mediterranean Basin, where it is a serious problem on ornamental Phoenix canariensis (Chabaud) palms. The efficacy of Steinernema carpocapsae (Weiser) (Nematoda: Steinernematidae) in a chitosan formulation (Biorend R^®) against this weevil in a semi-field trial including both preventative and curative assays has been studied. Our results prove the potential of this nematode to control R. ferrugineus. Efficacies around 80% were obtained in the curative assay, and up to 98% in the preventative treatment. Applications repeated every 2–3 weeks during the critical flight periods could prove effective to protect palms from this weevil in the Mediterranean Basin.     

Predation of entomopathogenic nematodes by <Emphasis Type="Italic">Sancassania</Emphasis> sp. (Acari: Acaridae)

Predation of the entomopathogenic nematode, Steinernema feltiae (Rhabditida: Steinernematidae), by Sancassania sp. (Acari: Acaridae) isolated from field-collected scarab larvae was examined under laboratory conditions. Adult female mites consumed more than 80% of the infective juvenile (IJ) stage of S. feltiae within 24 h. When S. feltiae IJs were exposed to the mites for 24 h and then exposed to Galleria mellonella (Lepidoptera: Pyralidae) larvae, the number of nematodes penetrating into the larvae was significantly lower compared to S. feltiae IJs that were not exposed to mites (control). Soil type significantly affected the predation rate of IJs by the mites. Mites preyed more on nematodes in sandy soil than in loamy soil. We also observed that the mites consumed more S. feltiae IJs than Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae). No phoretic relationship was observed between mites and nematodes and the nematodes did not infect the mites.     

A preliminary study on distributions and oviposition sites of <Emphasis Type="Italic">Drosophila suzukii</Emphasis> (Diptera: Drosophilidae) and its parasitoids on wild cherry tree in Tokyo,central Japan

Distributions and oviposition sites of Drosophila suzukii (Matsumura) and its parasitoids on wild cherry tree were studied in early summer in a suburb of Tokyo, central Japan. Adults of D. suzukii occurred in the foliage layer as well as in the undergrowth layer. The number of D. suzukii that emerged did not significantly differ between wild cherry fruit collected from the foliage layer and those from the undergrowth layer. In addition, the number of D. suzukii that emerged per fruit decreased when fruit were left on the ground longer. It is therefore assumed that D. suzukii females rarely oviposit eggs in fallen wild cherry fruit. The suzukii-associated type of Ganaspis brasiliensis (Ihering) was the major parasitoid that emerged from D. suzukii in the study area. The rate of parasitism by this parasitoid did not significantly differ between larvae in fresh fruit from the foliage layer and those in fallen fruit from the undergrowth layer. This may also suggest that this wasp rarely attacks D. suzukii larvae in fallen fruit. Adults of the suzukii-associated type of G. brasiliensis, Asobara sp. TK1, and Leptopilina japonica that attack D. suzukii were mainly collected from the foliage layer. On the basis of the present results, some proposals for the control of D. suzukii were discussed.     

Susceptibility and Interactions of <Emphasis Type="Italic">Drosophila suzukii</Emphasis> and <Emphasis Type="Italic">Zaprionus indianus</Emphasis> (Diptera: Drosophilidae) in Damaging Strawberry

Drosophila suzukii (Matsumura) has been recently detected causing damage to strawberries in Brazil. Infestation in strawberry culture has often been observed jointly with the presence of Zaprionus indianus Gupta. This study investigated the susceptibility of strawberries at three ripening stages to infestation of D. suzukii and Z. indianus and their interaction. In the laboratory, strawberries cv. Albion at different ripening stages (green, semi-ripe and ripe) were exposed to D. suzukii and Z. indianus for 24 h in choice and no-choice bioassays. Additionally, we evaluated the effects of mechanical damage incurred artificially or by D. suzukii oviposition on Z. indianus infestation. In no-choice bioassay, there were no significant differences in fruit susceptibility to D. suzukii infestation at different ripening stages. However, in choice bioassay, D. suzukii adults preferred to oviposit on R fruit. The presence of mechanical damage did not increase susceptibility of fruit to D. suzukii oviposition. For Z. indianus, there was greater susceptibility of R fruit in relation to SR and G fruit in both the choice and no-choice bioassays. There was a significant and positive interaction of mechanical damage and damage caused by D. suzukii to R fruit and infestation by Z. indianus, which was not observed in SR and G fruit. Although infestation of Z. indianus is related to attack damaged or decaying fruit, this work shows that this species has the ability to oviposit and develop in healthy strawberry fruit with and increased infestation level when the fruit has damage to its epidermis.     

Optimizing the application method of entomopathogenic nematode suspension for biological control of large pine weevil <Emphasis Type="Italic">Hylobius abietis</Emphasis>

Entomopathogenic nematodes (EPNs) are effective against the immature stages of the large pine weevil Hylobius abietis. In three field trials we compared the efficacy of the application method of EPN for weevil suppression below the suggested threshold of 20 weevils per stump: applying the EPN suspension in the top edges of the stumps (‘top’) vs. drenching the soil around stumps (‘standard’). For Steinernema carpocapsae, weevil suppression was below the targeted threshold only when suspension was applied in the standard way (two of the three sites). On the other hand, weevil suppression was provided in all three cases of ‘top’ application of Heterorhabditis downesi suspension, whereas suppression in ‘standard’ application was observed in one site. Percentage parasitism of developing weevils in relation to depth and distance help explain EPN movement post-application. Weevil suppression relative to suggested thresholds can be improved by altering the method of EPN application depending on the nematode species.     

Harmful effects of mustard bio-fumigants on entomopathogenic nematodes

Mustard (Brassica and Sinapis spp.) green manures tilled into the soil preceding potato crops act as bio-fumigants that are toxic to plant–parasitic nematodes, providing an alternative to synthetic soil fumigants. However, it is not known whether mustard green manures also kill beneficial entomopathogenic nematodes (EPNs) that contribute to the control of pest insects. We used sentinel insect prey (Galleria mellonella larvae) to measure EPN infectivity in Washington State (USA) potato fields that did or did not utilize mustard green manures. We found a trend toward lower rates of EPN infection in fields, where mustard green manures were applied, compared to those not receiving this cultural control method. In a series of bioassays we then tested whether the application of two mustard (Brassica juncea) cultivars, differing in glucosinolate levels, disrupted the abilities of a diverse group of EPN species to infect insect hosts. Mustard-exposure trials were conducted first in laboratory arenas where EPNs were exposed to mustard extracts suspended in water, and then in larger microcosms in the greenhouse where EPNs were exposed to green manure grown, chopped, and incorporated into field soil. In all trials we used G. mellonella larvae as hosts and included multiple EPN species in the genera Steinernema (Steinernema carpocapsae, Steinernema feltiae, Steinernema glaseri, and Steinernema riobrave) and Heterorhabditis (Heterorhabditis bacteriophora, Heterorhabditis marelatus, and Heterorhabditis megidis). In the laboratory, EPN infection rates were lower in arenas receiving mustard extracts than the control (water), and lower still when EPNs were exposed to extracts from plants with high versus low glucosinolate levels. Results were nearly identical when mustard foliage was soil-incorporated into greenhouse microcosms, except that the negative effects of mustards on EPNs developed more slowly in soil. Significantly, in arenas of both types one EPN species, S. feltiae, appeared to be relatively unaffected by mustard exposure. Together, our results suggest that the use of mustard bio-fumigants for the control of plant–parasitic nematodes has the potential to interfere with the biocontrol of insect pests using EPNs. Thus, it may be difficult to combine these two approaches in integrated pest management programs.     

<Emphasis Type="Italic">Drosophila suzukii</Emphasis> in Southern Neotropical Region: Current Status and Future Perspectives

Non-native insect pests are often responsible for important damage to native and agricultural plant hosts. Since Drosophila suzukii Matsumura (Diptera: Drosophilidae) has become an important pest in North America and Europe (i.e., in 2008), the global production of soft thin-skinned fruits has faced severe production losses. In the southern Neotropical region, however, the first record of D. suzukii occurred in 2013 in the south of Brazil. It has also been recorded in Uruguay, Argentina, and Chile. Despite its recent occurrence in the southern Neotropical region, the fast dispersion of D. suzukii has inspired local research efforts in an attempt to mitigate the consequences of this insect pest invasion. In this forum, we explore the current status of D. suzukii in southern Neotropical regions, discussing its future perspectives. Additionally, we attempt to draft activities and a research agenda that may help to mitigate the losses caused by D. suzukii in native and commercial soft-skinned fruits produced in this region. Currently, D. suzukii appears to be well established in the south of Brazil, but considering the entire southern Neotropical region, the invasion panorama is still underinvestigated. The lack of studies and regulatory actions against D. suzukii has contributed to the invasion success of this species in this region. Considering several peculiarities of both the pest biology and the environmental of this region, the authors advocate for the need of intensive and integrative studies toward the development and implementation of area-wide integrated pest management programs against D. suzukii in the southern Neotropical region.     

Influence of humidity and a surfactant-polymer-formulation on the control potential of the entomopathogenic nematode <Emphasis Type="Italic">Steinernema feltiae</Emphasis> against diapausing codling moth larvae (<Emphasis Type="Italic">Cydia pomonella</Emphasis> L.) (Lepidoptera: Tortricidae)

The codling moth (Cydia pomonella L.) is a serious pest of pome fruit. Diapausing cocooned larvae overwinter in cryptic habitats in the soil or in the bark of infested trees. The entomopathogenic nematode Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) is used to control diapausing codling moth larvae. The objective of this study was to define environmental conditions favouring the performance of the nematodes. Cocooned larvae were more susceptible than non-cocooned larvae. Susceptibility of pupae was low. To determine the influence of decreasing water activity (a_w-value) on the activity of the nematodes, mortality of codling moth larvae and Galleria mellonella L. were tested in sand-sodium-polyacrylate mixtures of variable water activity. S. feltiae was able to infect both insects at a_w-values >0.9. Cocooned larvae of both insects died at lower a_w-values than non-cocooned larvae. Mortality of cocooned larvae did not further increase after half an hour of exposure to nematodes, whereas the mortality of non-cocooned larvae increased with increasing exposure time. LC₅₀ and LC₉₀ considerably decrease with increasing RH. The negative influence of the relative humidity (macro environment) was less important than the effect of the water activity in the bark substrate (micro environment). The micro environment can be manipulated by applying S. feltiae with higher volumes of water. A surfactant-polymer-formulation significantly increased nematode efficacy and can buffer detrimental environmental effects.     

Susceptibility of Queensland fruit fly,Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), to entomopathogenic nematodes

Queensland fruit fly, Bactrocera tryoni (Froggatt), is the economically most significant Australian tephritid pest species with a large invasion potential, yet relatively little work on its biological control has been undertaken. Entomopathogenic nematodes (EPNs) are of potential interest for control of this fruit fly species as it pupates in the soil. Specifically, the pre-pupal stage of B. tryoni may present a unique window for EPN application, as fully developed larvae drop from infested fruit to the soil for pupation. For the first time, we tested the capacity of three EPN species with different foraging strategies, Steinernema feltiae, Steinernema carpocapsae and Heterorhabditis bacteriophora, to cause larval and pupal mortality in B. tryoni across a range of EPN concentrations (50, 100, 200, 500 and 1000 infective juveniles IJs cm^-2), substrate moisture (10, 15, 20 and 25% w/v) and temperatures (15, 20, 25 and 30 °C). We found that all EPN species tested caused environment and density dependent mortality in the third larval instar while pupae were not affected. Steinernema feltiae caused high mortality across different IJ concentrations and over a wider moisture and temperature range than the other two EPN species. High mortality caused by S. carpocapsae and H. bacteriophora was more limited to high IJ concentrations and a narrower moisture and temperature range. Our findings highlight the potential of EPNs for the control of B. tryoni and warrant further laboratory and field experiments to evaluate their efficacy under the wide environmental conditions that B. tryoni can occur in.     

Identification of active components from volatiles of Chinese bayberry, <Emphasis Type="Italic">Myrica rubra</Emphasis> attractive to <Emphasis Type="Italic">Drosophila suzukii</Emphasis>

Drosophila suzukii (Diptera: Drosophilidae) is native to Southeast Asia and now has become a severe pest of several soft fruits in Europe and the Americas. It causes considerable damage to Chinese bayberry, Myrica rubra, in China. In the present study, we employed gas chromatograph–electroantennographic detection (GC–EAD) together with behavioural bioassays and trapping experiments to identify volatile semiochemicals emitted by Chinese bayberry attracting D. suzukii. Electrophysiological experiments revealed the presence of six EAD-active compounds from ripe bayberry fruits, including methyl (E)-3-hexenoate, methyl (E)-2-hexenoate, ethyl (E)-2-hexenoate, α-ylangene, α-humulene and an unidentified compound that elicited consistent antennal response. In two-choice bioassays, bayberry fruits attracted all responding flies, and significantly more flies responded to the volatile extract of bayberry fruits. Four EAD-active compounds were attractive to mated female D. suzukii at lower doses (0.01 and 0.1 µg), but showed repellency at higher doses (10 and 100 µg). Mixtures of these four compounds at different ratios attracted D. suzukii flies at all test doses (0.1, 1 and 10 µg). Both male and female flies were trapped by a mixture of synthetic methyl (E)-3-hexenoate, methyl (E)-2-hexenoate, ethyl (E)-2-hexenoate and α-humulene in a ratio of 1:1.3:1:6.4 in the field trapping experiment. Significantly more males than females were captured in the trap baited with the synthetic blend, and the percentages of D. suzukii captured out of all flies by the traps baited with lure were higher than that baited with blank control. Our findings may provide insights into the olfactory responses of D. suzukii to specific host plant volatiles, and contribute to further development of an effective lure for monitoring D. suzukii in the field.     

Pathogenicity,reproduction and foraging behaviours of some entomopathogenic nematodes on a new turf pest,Dorcadion pseudopreissi (Coleoptera: Cerambycidae)

Entomopathogenic nematodes (EPNs) in the families Heterorhabditidae and Steinernematidae have considerable potential as biological control agents of soil-inhabiting insect pests. In the present study, the control potential of the EPNs Steinernema carpocapsae (TUR-S4), S. feltiae (Nemaplus), S. carpocapsae (Nemastar), S. feltiae (TUR-S3) and Heterorhabditis bacteriophora (Nematop) against a new longicorn pest, Dorcadion pseudopreissi Breuning, 1962 (Coleoptera: Cerambycidae), on turf was examined in laboratory studies. Pathogenicity tests were performed at the following doses: 50, 100 and 150 Dauer Juveniles (DJs)/larva at 25°C. Highest mortalities (75–92%) of the larvae were detected at the dose of 150 DJs/larva for all nematodes used. Reproduction capabilities of the used EPNs were examined at doses of 50, 75, 100 and 150 DJs/larva at 25°C. S. carpocapsae (TUR-S4) had the most invasions (32 DJs/larva) and reproduction (28042 DJs/larva) at the dose of 100 DJs, and the highest reproduction (per invaded DJ into a larva) was observed in H. bacteriophora (Nematop) (2402.85 DJs) at a dose of 50 DJs. The foraging behaviour of the nematodes in the presence of D. pseudopreissi and Galleria mellonella L. (Lepidoptera: Galleriidae) larvae was studied using a Petri dish filled with sand at 20°C. All of the used nematodes accumulated near the larvae section of both insect species (32–53% of recovered DJs) with a higher percentage of S. carpocapsae (TUR-S4) (53%) and H. bacteriophora (48%) (Nematop) moving towards larvae of D. pseudopreissi, than the S. feltiae strains.     

Genetic differentiation of <Emphasis Type="Italic">Ganaspis brasiliensis</Emphasis> (Hymenoptera: Figitidae) from East and Southeast Asia

Ganaspis brasiliensis (Ihering) (Hymenoptera: Figitidae: Eucoilinae) is a Drosophila parasitoid that has often been misidentified as G. xanthopoda (Ashmead) in recent studies. This study aims to clarify genetic differentiation of G. brasiliensis based on the nucleotide sequences of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene and three nuclear DNA regions, the inter-transcribed spacers 1 and 2 (ITS1 and ITS2) and putative 60S ribosomal protein L37 (RpL37), as well as crossing experiments. Four lineages are recognized in individuals assigned as G. basiliensis by morphology, (1) individuals occurring in Japan and probably South Korea, (2) individuals from a small subtropical island of Japan, Iriomote-jima, (3) individuals from temperate lowlands of Japan and high altitude areas of Southeast Asia, and (4) individuals occurring widely in Asia, America, Hawaii and Africa. The first lineage is a specialist of Drosophila suzukii (Matsumura), a pest of fresh fruit, and also the fourth lineage has a capacity to parasitize this pest species. The first, third and fourth lineages occur sympatrically at least in Tokyo. The third and fourth lineages differed in mate choice and host use to some extent, but post-mating isolation between them was almost absent.     

Post-application of anti-desiccant agents improves efficacy of entomopathogenic nematodes in formulated host cadavers or aqueous suspension against diapausing codling moth larvae (Lepidoptera: Tortricidae)

Codling moth (CM), Cydia pomonella (L.) is the most serious pest of apple and other pome fruit worldwide. In temperate climates, diapausing cocooned larvae make up 100% of the population. Control of this stage would reduce or eliminate damage by first generation CM in late spring and early summer. Entomopathogenic nematodes (EPNs) are good candidates for control of CM in the cryptic habitats where the larvae overwinter. The two predominant limiting factors for EPNs are adequate moisture and temperatures below 15°C. Formulation that maintains moisture and enables survival of EPN infective juveniles (IJs) until they can infect overwintering larvae would significantly improve their utility for protection of apple, pear and walnut. In laboratory studies conducted in moist mulch (consisting of apple and conifer wood), Galleria mellonella (L.) larvae infected with Steinernema carpocapsae (Weiser), S. feltiae (Filipjev), or Heterorhabditis bacteriophora Poinar and coated with starch and clay, produced mean mortalities of 42, 88, and 24%, respectively in CM larvae. Mulched field plots treated with formulated S. carpocapsae- or S. feltiae-infected G. mellonella larvae, then followed by an application of wood flour foam as an anti-desiccant, resulted in 56 and 86% mortality, respectively. Comparative tests of aqueous suspensions of S. carpocapsae IJs applied to cardboard bands on apple tree trunks followed by water, fire retardant gel or foam resulted in 11, 35, and 85% respective mortalities. Identical tests with S. feltiae resulted in 20, 19, and 97% respective mortalities. Our research with cadaver formulations of EPNs in mulch and aqueous suspensions on tree trunks combined with anti-desiccant agents, demonstrated significant improvement in larvicidal activity for diapausing cocooned CM larvae.     

Natural occurrence of entomopathogenic nematodes in Liaoning (Northeast China)

Entomopathogenic nematodes (EPNs) can provide effective biological control of pest. In order to contribute to knowledge on these organisms for regional biological control programs, we studied EPN distribution and ecological requirements in Liaoning Province, Northeast China. One hundred and forty-nine soil samples were taken from 36 locations. EPNs were recovered from 22 of the 36 locations (61.11%). Forty-four samples contained steinernematids (89.80%) and 5 samples contained heterorhabditids (10.20%). EPN recovery varied among the different soil and habitat type. Most EPNs were isolated from sandy loam, and most of the samples containing EPNs were collected from woodland and fruit crop habitats. The morphological characters of infective juveniles were used for preliminary species diagnosis. We preliminarily identified 15 species of Steinernematidae (Steinernema litorale, Steinernema silvaticum, Steinernema feltiae, Steinernema bicornutum, Steinernema robustispiculum, Steinernema affine, Steinernema riobrave, Steinernema yirgalemense, Steinernema kushidai, Steinernema scapterisci, Steinernema carpocapsae, Steinernema ritteri, Steinernema tami, Steinernema rarum and Steinernema sasonense) and 4 species of Heterorhabditidae (Heterorhabditis megidis, Heterorhabditis zealandica, Heterorhabditis brevicaudis and Heterorhabditis bajardi).