Potential of entomopathogenic nematodes to control banana leaf and fruit scarring beetle, Basilepta subcostatum

Relative virulence, host finding ability, and reproductive capacity of entomopathogenic nematodes for control of the goat biting louse Bovicola caprae (Phthiraptera: Trichodectidae).

Description of the subject. The article deals with the study of compatibility of entomopathogenic nematode (EPN) species with insecticides currently used against diamondback moth (DBM) Plutella xylostella (L.) in northern Benin Objectives. The aim of this work was to determine the impact of five insecticides on the efficacy of entomopathogenic nematodes against DBM larvae. Method. Infective juveniles (IJs) of two EPN species (Steinernema sp. 83a and Heterorhabditis sonorensis KF723827) were exposed to five insecticides used against P. xylostella larvae in Djougou for 48 h. The number of surviving nematodes was used to infest DBM larvae. The experiment was carried out under laboratory and semi-field conditions. Results. The bioassays carried out in laboratory showed that the survival rate of nematodes exposed to KARATE 2.5 WG, LAMBDA SUPER 2.5EC or neem oil ranges between 95% and 98%. In the treated plots, Steinernema sp. 83a was the most virulent with the highest P. xylostella mortality (87% at 50 IJs·cm-2 after 24 h) while only 35% larval mortality was recorded for H. sonorensis applied at the same dose. Population density of nematodes which penetrated DBM larvae reached 9 ± 3I IJs·larva-1 for H. sonorensis KF723827 and 6 ± 2 IJs·larva-1 for Steinernema sp. 83a. In cadaver of DBM, nematode reproduction did not appear to be affected by the contact with insecticides. Conclusions. Based on our research, we conclude that the three insecticides did not affect EPNs efficiency and could be used in combination against DBM.

Scavenging behavior and interspecific competition decrease offspring fitness of the entomopathogenic nematode Steinernema feltiae.

Potential use of entomopathogenic nematodes against the soil dwelling stages of onion thrips, Thrips tabaci Lindeman: Laboratory, greenhouse and field trials

Physiological defense of the white grub, Polyphylla adspersa Motschulsky (Col., Scarabaeidae) against entomopathogenic nematodes

Entomopathogenic nematode (EPN) species richness merits studies towards making rational decisions for effective management of Caribfly, Anastrepha suspensa (Loew) in southern Florida. Competition for Caribfly and efficacies of EPN biodiversity were examined under laboratory conditions. Similar EPN species treatments to Caribfly-infested fruits, periodically obtained from the ground in groves which were also infested by the parasitoid Diachasmimorpha longicaudata Ashmead (Braconidae), were studied in a series of field trials. Treatments with individual EPN species and their mixtures caused similar mortalities of Caribfly larvae, though the various EPN species competed for larvae in multiple-species treatments. Laboratory trials showed that mortalities of EPN-treated Caribfly pupae were mostly inversely related to EPN diversity. In the field, population densities of emerging adult Caribfly increased with increasing number of EPN species combined in treatments. Thus, single-EPN species treatments proved to be more effective for the management of fruit-to-soil stages of Caribfly. Relative to controls, the proportions of surviving adult Caribfly observed in EPN treatments with Heterorhabditis bacteriophora (exotic in Florida), Steinernema feltiae (exotic EPN) and Heterorhabditis indica (the endemic species) in field plots were 22.5 ± 6, 45 ± 13 and 47 ± 13%, respectively. Number of emerging D. longicaudata in each of EPN species treatments was similar to that observed in control, suggesting that none of the EPN species significantly affected the emergence of D. longicaudata, a parasitoid of Caribfly. Heterorhabditis bacteriophora will be more promising, with insignificant side effects on D. longicaudata in Caribfly-integrated pest management.

Laboratory studies were conducted to determine whether combining two entomopathogenic nematode species would result in superior control effects against insect targets than the application of single species. This study aimed to achieve the following objectives (1) to find out if the applications of two different species at the same time can increase the efficacy compared to the application of a single species and (2) to examine if the difference in the efficacy of mixed and single applications might be caused by changes in the invasion of the two applied species and lastly (3) to investigate how mixed applications influence the propagation of the nematodes in the host. The exemplary studies were carried out with last larval instars of Tenebrio molitor and the 2nd stage larvae of Diabrotica virgifera virgifera. The nematodes used in the experiments were Heterorhabditis bacteriophora, Steinernema feltiae, Steinernema carpocapsae and Steinernema kraussei. In laboratory bioassays, lethal dosages that resulted in the average in 50 % mortality (LD50) were used for the single species applications in comparison to the respective LD25 of each of the two species in the mixed applications of the nematode species. In the assays with T. molitor the invasion of this host by the infective juveniles (IJs), the mortality of the insects and the emigration of the next generation of IJs were quantitatively assessed. In the assays with Diabrotica larvae only the insect mortality was assessed. Invasion of IJs for each species in the mixed applications were not significantly different from the expected numbers. However, invasion was lower in the mix than in the single species applications due to the lower dosage used in the mixtures. This had no negative effect on the efficacy against the insects and on the number of IJs which finally emerged from the cadavers. Emergence was even higher for the mixtures. The mortality of the insects was in most cases higher for the mixed applications, indicating synergistic effects. However, the efficacy of the mixtures were species specific. The efficacy of mixtures with H. bacteriophora were superior over mixtures of steinernematids against Diabrotica, but inferior against Tenebrio. We conclude that combining nematodes species might be more effective in the field, because of the stronger dose effect and higher propagation rate of the EPN.

Effect of insect cadaver desiccation and soil water potential during rehydration on entomopathogenic nematode (Rhabditida: Steinernematidae and Heterorhabditidae) production and virulence

Caribbean fruit fly, also known as Caribfly or Anastrepha suspensa , is a major tephritid pest of guavas. A virulent entomopathogenic nematode (EPN) species was investigated to suppress the fruit-to-soil stages of Caribflies, which are also attacked by the koinobiont parasitoid Diachasmimorpha longicaudata in south Florida. The main objective was to develop a feasible and cost-effective EPN-application method for integrated pest management (IPM) of Caribfly to improve guava production. Naturally infested guavas were treated with increasing Heterorhabditis bacteriophora infective juvenile (IJ) concentration or rate (0, 25, 50, …, 1,600 IJs cm -2 ) in field trials to measure the optimum IJ rate and then examine sensitivity of producing guavas to inclusion of Heterorhabditis bacteriophora in Caribfly IPM plans. Relative survival of Caribfly in treatments significantly decreased with increasing IJ rate from 0 to 100 IJs cm -2 . Similarly, probability of observing large numbers of parasitoid wasps ( Diachasmimorpha longicaudata ) in EPN treatments significantly declined with increasing IJ rate (0-100 IJs cm -2 ), even though the non-target effects of Heterorhabditis bacteriophora on relative survival of Diachasmimorpha longicaudata could not be determined because of few emerging parasitoid wasps. Optimum suppression (⩾ 60%) of Caribfly was consistently achieved at 100 IJs cm -2 or 17,500 IJs fruit -1 . Profitability analysis showed that Heterorhabditis bacteriophora can be included in Caribfly IPM tactics to produce guavas. Costs of EPNs in Caribfly IPM are minimized if Heterorhabditis bacteriophora is strategically applied by spot treatment of fruit. Repayment of costs of EPN-augmentation by spot treatments appears achievable by recovering 5.71% of the annual yield losses (⩾1,963 kg ha -1 ≈ US$ 8,650 ha -1 ), which are largely due to Caribfly infestation. Hectare-wide EPN-augmentation (or broadcasting) method requires more fruit recovery than the total annual yield losses to repay its high costs. Profitability of guava production in south Florida will not be very sensitive to marginal costs of the spot treatment method, when compared to the field-wide broadcasting of Heterorhabditis bacteriophora .

The efficacy of three entomopathogenic nematode (EPN) species, Heterorhabditis indica, Steinernema thermophilum, and S. glaseri, from Meghalaya, India was studied against the larvae of taro leaf beetle, Aplosonyx chalybaeus (Hope) (Coleoptera: Chrysomelidae), under the laboratory conditions. The beetle larvae (grubs) were exposed to 25, 50, 75, 100 and 200 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 grubs to nematode infection varied according to the dosages of IJs and their exposure periods. Appreciably good performance was achieved by S. glaseri, which showed 100% mortality of insect larvae in 48h exposure time. At 48h of incubation, its LC50 value was 90.3 IJs/larva, which was lower than that of S. thermophilum (115.0 IJs/larva) and H. indica (186.0 IJs/larva), at the same exposure time. All the tested nematode species were also found to reproduce within the host and produced infective juveniles. H. indica, however, showed comparatively more production of IJs per cadaver of infected host (168.9×10(3) IJs/larva), as compared to the other two tested nematode species. The production of IJs per cadaver of infected host by S. thermophilum was recorded to be 82.0×10(3) IJs/larva. In case of S. glaseri, while production of IJs increased initially to 18.9×10(3) IJs/larva at concentration of 100 IJs/larva, it declined thereafter to 14.7×10(3) IJs/larva at the dose of 200 IJs/larva. In conclusion, the evidence obtained in this study suggests that all the three indigenous EPN species are virulent enough to produce 100% mortality in the last instar larvae of A. chalybaeus. These EPN species thus have potential scope for the management of A. chalybaeus in taro crops.

BackgroundCompatibility of entomopathogenic nematodes (EPNs) with insecticides is a crucial mainstay of integrated pest management (IPM) programs. This study was designed to evaluate the joint action of EPN species and insecticides when employed to deter 3rd and 4th larval instars of cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae) under laboratory conditions. EPNs [Steinernema carpocapsae (All strain), S. feltiae (Filipjev), Heterorhabditis bacteriophora (HP88), and H. bacteriophora (Ar-4)], at concentrations of 50, 100, and 125 IJs/larva, were tested with 3 insecticides (lambda-cyhalothrin, emamectin benzoate, and indoxacarb) at LC25 and LC50 values. Additionally, expression profiles of 2 detoxification genes (CYP6AE120 and PrGSTs1) when the 4th instar larvae were treated by H. bacteriophora (HP88) and lambda-cyhalothrin were examined.ResultsData indicated that statistically significant mortality of 2 larval instars of P. rapae was observed in vitro among EPN species and pesticide concentrations. At concentration of 50 IJs/larva, LT50 values were 2.385 and 3.92 days for S. carpocapsae (All strain) and H. bacteriophora(Ar-4), respectively, on 3rd instar larvae; also, these values were 3.506 and 3.107 days for S. feltiae and H. bacteriophora (Ar-4), respectively, on 4th instar larvae Lambda-cyhalothrin was the most toxic insecticide, followed by emamectin benzoate and indoxacarb at LC25 and LC50, respectively. An additive effect was observed between EPN species with LC25 and LC50 of the tested insecticides, except for lambda-cyhalothrin at LC50 with H. bacteriophora (Ar-4), and indoxacarb, with all EPNs showing antagonistic effects on mortality of 3rd instar larvae after 3 days post-treatment. The interaction between the tested pesticides at LC25 and LC50 and EPN species, showed an additive effect, excluding lambda-cyhalothrin at LC25 with S. carpocapsae (All strain) and LC25 of indoxacarb with H. bacteriophora (Ar-4), which showed potentiation effects. The interaction of S. feltiae (Filipjev) with tested insecticides at LC50 exhibited an antagonistic effect on the mortality of 4th instar P. rapae larvae after 3 days post-treatment. The expression of both CYP6AE120 and PrGSTs1 was significantly up-regulated with lambda-cyhalothrin, followed by H. bacteriophora (HP88) compared to control.ConclusionsThe findings suggested that combining EPNs and the pesticide concentrations can be a practical strategy for managing P. rapae and could pave the way to using new control technologies in protecting organic farm vegetables from lepidopteran pests.

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

The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) which was first detected in Izmir Province, Turkey in 2009 has spread quickly and has become the major pest in tomato producing areas. The efficacy of three different entomopathogenic nematode (EPN) species isolates (from e-nema GmbH Schwentinental, Germany), Heterorhabditis bacteriophora (Poinar), Steinernema carpocapsae (Weiser) and Steinernema feltiae (Filipjev) was investigated against T. absoluta during 2013-2014 under laboratory conditions. The EPNs were applied with different inoculation rates (1, 2, 5, 10, 15, 20, 25 and 40 infective juveniles per larva) for each species to the third instar larvae of T. absoluta outside the leaves. The mortality rates for H. bacteriophora, S. carpocapsae and S. feltiae were found between 21.2 -74.2%, 28.8 -99.4% and 17.5 -95.2%, respectively. According to the results, S. carpocapsae and S. feltiae caused similar mortalities at the given inoculation rates while H. bacteriophora had lower efficacy compared to those two species. The values of LD50 for H. bacteriophora, S. carpocapsae and S. feltiae were 21.67, 7.13 and 6.25 infective juveniles per larva, respectively. Based on these data, S. feltiae was the most efficient nematode species, and was then applied against the larva of T. absoluta inside the mines and pupae. However, S. feltiae only caused low mortality of larvae both inside mines (19%) and the pupae (7%). These results revealed that EPN have good potential for the control of T. absoluta larvae outside the leaves and should be studied further.

Simple SummaryThe plum curculio, a snout beetle native to North America, is one of the most important fruit-feeding pests of cultivated blueberry in New Jersey. Application of certain entomopathogenic nematode (EPN) species has shown efficacy in plum, peach, and apple orchards when targeting the larval stage of plum curculio in soil. Prior to our research, however, EPNs have never been tested for control of this pest in highbush blueberries. In 2020, laboratory and field studies were conducted to: (1) determine the persistence of different EPN species in acidic blueberry soil; (2) compare the virulence of these EPNs to plum curculio larvae and pupae; and (3) compare the efficacy of these EPNs to control this pest in blueberry fields. In 2021, field studies were conducted to confirm the efficacy of one of the EPN species. Steinernema riobrave persisted better in blueberry sand, was the most virulent EPN against plum curculio larvae and pupae and was highly efficacious for suppression of larvae and pupae of this pest in blueberry fields. Steinernema riobrave has the potential to become an important component in the management of plum curculio in highbush blueberry.Conotrachelus nenuphar Herbst (Coleoptera: Curculionidae) is a key pest of stone and pome fruits in the United States. Application of certain entomopathogenic nematode (EPN) species has shown efficacy in some crops when targeting the larval stage of C. nenuphar in soil. To date, however, no EPNs have been tested for the control of this pest in highbush blueberries. In 2020, laboratory and field studies were conducted to: (1) determine the persistence of Steinernema riobrave, S. carpocapsae, S. feltiae, and Heterorhabditis bacteriophora in acidic blueberry soil; (2) compare the virulence of these EPNs to C. nenuphar larvae and pupae; and (3) compare the efficacy of these EPN species to control this pest in blueberry fields. The greatest persistence in blueberry soil was exhibited by S. riobrave followed by S. carpocapsae. Superior virulence was observed in S. riobrave against C. nenuphar larvae and pupae. Promising levels of virulence were also observed in S. carpocapsae and S. feltiae against the larvae, but S. scarabaei had low virulence. In the field, S. riobrave provided significantly higher levels of C. nenuphar suppression (90%) than the other EPNs. The field efficacy of S. riobrave against C. nenuphar at low and high rates was confirmed in 2021. Steinernema riobrave has the potential to become an important component in the management of C. nenuphar in highbush blueberry.

The biological traits of the entomopathogenic nematodes (EPNs), Steinernema carpocapsae and Heterorhabditis bacteriophora, against the larvae of the leopard moth, Zeuzera pyrina were evaluated in the laboratory. The traits included pathogenicity, penetration potential as well as foraging behaviour. Plate assays were performed using a range of EPN concentrations (5, 10, 20, 50 and 100 infective juveniles (IJs) per larva). The LC50 values for S. carpocapsae and H. bacteriophora were 6.4 and 8.4 IJs larva−1 after 72 h. Both EPN species caused high mortality in branch experiments. Significantly higher mortality rates occurred in the larger larvae after exposure to S. carpocapsae. Both EPN species successfully penetrated the Z. pyrina larvae as well as larvae of Galleria mellonella L. (Lepidoptera: Galleridae).The proportional response of H. bacteriophora to host-associated cues was strongly higher than S. carpocapsae in Petri dishes containing agar 1, 12 and 24 h after EPN application. These results highlight the efficiency of EPNs for the control of Z. pyrina larvae. However, due to the cryptic habitat of Z. pyrina larvae in their galleries in the trees, field trails need to be conducted to further evaluate this potential.