Heterorhabditis Bacteriophora Research Articles

Entomopathogenic nematodes occurring in alfalfa fields

With this study, the presence of entomopathogenic nematodes (EPN) in 15 villages (Ulaş, Taşlıçiftlik, Söngüt, Büyükbağlar, Uğrak, Tahtoba, Dayılıhacı, Çördük, Kızılköy, Bakışlı, Ballıdere, Çöreğibüyük, Gaziosmanpaşa, Günevi, Akyamaç and 2 towns (Güryıldız, Emirseyit) of Tokat province where alfalfa was cultivated intensively was investigated between June-October 2016. For this purpose, 58 soil samples were taken and obtained 10 EPN isolates by trap-insect method. As a result of the morphological and molecular diagnosis, 8 of them were defined as Steinernema carpocapsae, one isolate as S.feltiae and one isolate as Heterorhabditis bacteriophora. This paper is the first report showing the occurrence of EPNs in alfalfa fields in Turkey.

Volatile organic compounds of Metarhizium brunneum influence the efficacy of entomopathogenic nematodes in insect control

The entomopathogenic fungus (EPF) Metarhizium brunneum occupies the same ecological niche as entomopathogenic nematodes (EPN), with both competing for insects as a food source in the rhizosphere. Interactions between these biocontrol agents can be antagonistic or synergistic. To better understand these interactions, this study focussed on investigating the effect of M. brunneum volatile organic compounds (VOCs), 1-octen-3-ol and 3-octanone, on EPN survival and behaviour. These VOCs proved to be highly toxic to the infective juveniles (IJs) of the EPN Steinernema carpocapsae, Steinernema feltiae and Heterorhabditis bacteriophora with mortality being dose dependent. Chemotaxis studies of H. bacteriophora IJs in Pluronic F127 gel revealed significant preference for the VOCs compared with controls for all tested concentrations. The VOCs also impacted on the test insects in a dose-dependent manner with 3-octanone being more toxic to Galleria mellonella, Cydia splendana and Curculio elephas larvae than 1-octen-3-ol. Mortality of C. splendana and G. mellonella larvae was significantly higher when exposed to relatively high doses (>25%) of 3-octanone. Lower doses of 3-octanone and 1-octen-3-ol immobilised test insects, which recovered after exposure to fresh air for 2 hrs. In depth studies on H. bacteriophora showed that exposure of IJs to > 10% concentration of 3-octanone or 1-octen-3-ol negatively affected infectivity whereas exposure to lower doses (0.1%, 0.01%) had no effect. The VOCs affected IJs, reducing penetration efficacy and the number of generations inside G. mellonella but they failed to inhibit the bacterial symbiont, Photorhabdus kayaii. The ecological significance of VOCs and how they could influence EPF-EPN insect interactions is discussed.

Combination of entomopathogenic nematodes with acaricides or essential oil of Lippia triplinervis against Rhipicephalus microplus (Acari: Ixodidae).

This study aimed to evaluate the combination effect of Heterorhabditis bacteriophora HP88 and H. indica LPP1, with the acaricides deltamethrin, amitraz and chlorfenvinphos, and the essential oil (EO) of Lippia triplinervis, against engorged females of Rhipicephalus microplus. In order to verify the effect of acaricides and EO, the adult immersion test was used, and in the groups treated only with entomopathogenic nematodes (EPNs), 150 infective juveniles were used per female. In the treatments with nematodes in combination with the acaricides or EO, the females were immersed in the solutions (acaricide or EO) and then transferred to Petri dishes for application of the nematodes. The treatment with acaricides resulted in a control percentage lower than 70%, except in the group treated with chlorfenvinphos in the second experiment (84.3%). The control percentage was 73% for L. triplinervis EO, and greater than 90% in all the groups treated with nematodes. For treatments with EPNs combined with the acaricides or EO, the efficacy was greater than 95% (except for deltamethrin + HP88), and reached 100% in the treatment with LPP1+amitraz. It can be concluded that the EPNs at the concentrations tested were compatible with the acaricides deltamethrin, amitraz and chlorfenvinphos, and with the EO of L. triplinervis. These combinations enhance the effect of these control agents.

Laboratory assay of entomopathogenic nematodes against the elm leaf beetle, Xanthogaleruca luteola Müller (Col.: Chrysomelidae)

The susceptibility of the elm leaf beetle, Xanthogaleruca luteola Müller (Col.: Chrysomelidae), 3<sup style="text-align: justify;">rd</sup> instar larvae and adults to the entomopathogenic nematodes Steinernema feltiae, S. carpocapsae, and Heterorhabditis bacteriophora was determined in laboratory assays. Larval mortality was assessed at 0, 16, 32, 48, 64, 80, 96, and 112 h after exposure of the larvae and adults to six concentrations (0, 100, 200, 300, 400, and 500) of infective juveniles (IJs) per mL. The median lethal concentration (LC<sub>50</sub>) values for each nematode species against the larvae and adults of X. luteola were 167.59 and 6.73 IJ·mL<sup style="text-align: justify;">–1</sup> for S. feltiae, 218.23 and 204.09 IJ·mL<sup style="text-align: justify;">–1</sup> for S. carpocapsae, and 338.66 and 70.29 IJ·mL<sup style="text-align: justify;">–1</sup> for H. bacteriophora, respectively. Also, the median lethal time (LT<sub>50</sub>) values for each nematode species against the larvae and adults of X. luteola were 44.51 and 22.23 h for S. feltiae, 50.78 and 36.17 h for S. carpocapsae, and 67.64 and 34.71 h for H. bacteriophora, respectively. The S. feltiae nematode was the most effective species in controlling the larvae and adults of the elm leaf beetle, X. luteola. Based on these and other results, the research could be expanded on the prospects of using entomopathogenic nematodes, especially S. feltiae, in managing of the elm leaf beetle, X. luteola.

Bazı entomopatojen nematodların etkinliğinin Patates güvesi Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae)’nin mücadelesinde değerlendirilmesi

Bu çalışmada Türkiye’den izole edilen entomopatojen nematodların (EPN) patates güvesi Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae) son dönem larvalarına karşı etkinlikleri laboratuvarda araştırılmıştır. Çalışmada Steinernema affine Bovien, S. carpocapsae Weiser, S. feltiae Filipjev ve Heterorhabditis bacteriophora Poinar EPN türleri kullanılmıştır. Patates güveleri, Derinkuyu’daki (Nevşehir) bulaşık patates tarlalarından 2019 haziran ayında toplanmıştır. Etkinlik denemeleri 9 cm çapındaki plastik Petrilerde 25 oC’de 50 infektif larva (IJ)/larva olacak şekilde yürütülmüştür. Denemenin kontrolleri 24, 48, 72 ve 96 saat aralıklar ile yapılmıştır. EPN türlerinin, P. operculella larvalarında meydana getirdiği ölüm oranları süreye bağlı olarak artış göstermiştir. EPN uygulamaları sonrası ölüm oranları 1. günden 4. güne kadar sırası ile %40-66.6, %83.3-100, %93.3-100 ve %96.6-100 arasında değişmiştir. Steinernema feltiae uygulamalarından sonraki 2. günde zararlı larvalarında %100 ölüm meydana gelmiştir. Denemede kullanılan tüm EPN türleri süreye bağlı olarak P. operculella larvalarında yüksek oranda ölüme neden olmuştur. Bu sonuçlar zararlı ile mücadelede EPN’lerin kullanım potansiyellerinin detaylı araştırılmasını gerektirmektedir.

Dissemination of Isaria fumosorosea Spores by Steinernema feltiae and Heterorhabditis bacteriophora.

Entomopathogenic nematodes and fungi are globally distributed soil organisms that are frequently used as bioagents in biological control and integrated pest management. Many studies have demonstrated that the combination of biocontrol agents can increase their efficacy against target hosts. In our study, we focused on another potential benefit of the synergy of two species of nematodes, Steinernema feltiae and Heterorhabditis bacteriophora, and the fungus Isaria fumosorosea. According to our hypothesis, these nematodes may be able to disseminate this fungus into the environment. To test this hypothesis, we studied fungal dispersal by the nematodes in different arenas, including potato dextrose agar (PDA) plates, sand heaps, sand barriers, and glass tubes filled with soil. The results of our study showed, for the first time, that the spreading of both conidia and blastospores of I. fumosorosea is significantly enhanced by the presence of entomopathogenic nematodes, but the efficacy of dissemination is negatively influenced by the heterogeneity of the testing arena. We also found that H. bacteriophora spread fungi more effectively than S. feltiae. This phenomenon could be explained by the differences in the presence and persistence of second-stage cuticles or by different foraging behavior. Finally, we observed that blastospores are disseminated more effectively than conidia, which might be due to the different adherence of these spores (conidia are hydrophobic, while blastospores are hydrophilic). The obtained results showed that entomopathogenic nematodes (EPNs) can enhance the efficiency of fungal dispersal.

Chemotaxis behaviour of Steinernema carpocapsae in response to Galleria mellonella (L.) larvae infected by con- or hetero-specific entomopathogenic nematodes

ABSTRACT Entomopathogenic nematodes (EPNs) infect insects and reproduce within the host cadaver. The nematodes use chemotaxis to assist in host-finding. However, the chemotaxis of nematode species in response to insects previously infected by con- and hetero-specific EPN in a sand context has rarely been reported. Our aim was to address the response of Steinernema carpocapsae All (Sc) to Galleria mellonella cadavers infected by con- or hetero-specific EPNs (Heterorhabditis bacteriophora HB1, S. feltiae SN, S. rarum 17 C&E) in sand via chemotaxis assays. Additionally, the effect of different time points post-infection was also evaluated. Results indicated that previously infected G. mellonella larvae repelled infective juveniles (IJs) of Sc (p < 0.05) regardless of the time point post-infection and EPN species (con- or hetero-specific) and had a lower chemotaxis index as compared to that of no larvae addition in both sides. Moreover, it was found that for each of four tested EPN species, EPNs infected insect cadavers released dimethyl disulphide, which was identified by solid-phase microextraction (SPME) coupled to gas chromatography–mass spectrometry (GC–MS). We found that dimethyl disulphide acted as a repellent to Sc infective juveniles and reached a significant effect at the level of 0.106 mol/L. Our findings could provide a better understanding of movement behaviour of EPN infective juveniles in response to insect resources in the presence of con- or hetero-specific EPNs.

Response of grey slug to entomopathogenic nematodes

ABSTRACT Biological control using entomopathogenic nematodes (EPNs) is known as an ecofriendly strategy in integrated pest management. The terrestrial slug Parmacella ibera is a major pest of vegetables and citrus trees in north of Iran. The heavy costs and environmental concerns of synthetic molluscicides led the study to use EPNs, against the slug P. ibera. The present study was arranged to evaluate and compare the performance of EPNs, Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora on P. ibera population (mortality rate) and the feeding rate in vitro, and also its damage (seedlings establishment rate) in vitro. Phasmarhabditis hermaphrodita, as a slug parasite nematode, and also the metaldehyde, as a molluscicide, were used as positive controls. The results of the study showed that the highest mortality rate (%) and the seedlings establishment rate (%) of the slug population were observed in S. carpocapsae, S. feltiae and H. bacteriophora treatments, respectively. The feeding rate (%) of the slug declined in the treatments with H. bacteriophora, S. feltiae and S. carpocapsae, respectively. The mortality rate of the pest was enhanced by extending the exposure time and increasing levels of the nematodes. Therefore, it can be concluded that the EPNs S. carpocapsae, S. feltiae and H. bacteriophora are able to control the slug P. ibera population.

Influence of Temperatures on Storage of Formulated Entomopathogenic Nematodes

Due to entomopathogenic nematodes EPNs represent excellent biological control agents for soil stages of several insect pests. This work aimed to study the influence of the different temperatures on the survival and vitality of EPN IJs after a long-term duration, and evaluate the suitability of EPNs, for formulation and storage on Hydrogel was used as a carrier medium. The new method was used for storage of IJs that was pieced in a square shape of Baby diapers which containing of Hydrogel (SAP), and fine cotton fibers to offer the moisture for IJs. Four EPNs were investigated, three of them were foreign, Steinernema carpocapsae (S.c.), Steinernema glaseri (S. g.), Heterorhabditis bacteriophora (H.b.), and one indigenous, Heterorhabditis indica (RM1). The tested EPNs divided into two main groups, the first group was stored at room temperature for 4 months, and the second was stored in the refrigerator for a long-term period extended up to 12 months. The survival and pathogenicity of the formulated EPNs were discussed. Results of the EPNs, which were stored at room temperature (group 1), showed that survival % of (RM1) and (S. g.) IJs were more than the others two (S. c.) and (H. b.). Also, (RM1) and (S. g.) achieved high pathogenicity % of the tested wax moth larvae, Galleria mellonella, morethan (S. c.) and (H. b.). The data showed excellent success in case of storage of EPNs IJs at low temperature (group 2), where all EPNs remained survive with percentage 100% for 5 months, while the survival of (S. g.) was 100% after 10 months, followed by (RM1) with survival 100% after 8 months, and (S. c.) as a long-term for 7 months. All EPNs species showed high vitality and infected the G. mellonella larvae with pathogenicity % reached to 85 %, 78%, 76%, and 72% by (S. g.), (S. g.), (S. c.), and (H. b.), respectively as storage long-term period expanded to 12 months.

Pathogen‐mediated modulation of host metabolism and trophic interactions in Spodoptera littoralis larvae

AbstractThe success and sustainability of entomopathogens in insect control depend on their stress potential and ability to modulate certain physiological aspects of their insect hosts. In the present study, newly moulted fourth instars of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) were incubated for 24 h with the median lethal dose (LD50) of Steinernema riobrave, Heterorhabditis bacteriophora, or Beauveria bassiana to determine their effects on certain metabolic activities and nutritional physiology compared to those of uninfected (control) larvae. Infection decreased total protein, lipid, and carbohydrate contents. Carbohydrase activity was found to be pathogen and enzyme dependent, with S. riobrave and H. bacteriophora infection increasing amylase, invertase, and trehalase activities. Beauveria bassiana infection decreased amylase and invertase activities but increased that of trehalase. Infection with the three pathogens also enhanced phosphatase activity. All pathogens reduced transaminase activity. Changes in the nutritional indices varied not only with the variation in the candidate entomopathogen and surviving instar but also with the variation in the age of the same instar, with a profound change in late last instars (3‐day‐old sixth instars). The link between the metabolic activities and nutritional indices was discussed. Overall, the entomopathogen‐host interaction appears to be primarily nutritional. The pleiotropic effects of the median lethal infections on the insect pest might eventually help in the biological control potential of the entomopathogens tested.

Desiccation stress tolerance of Steinernema australe and Heterorhabditis bacteriophora

South African entomopathogenic nematodes (EPNs), Steinernema australe and Heterorhabditis bacteriophora were used for studying the responses of infective juveniles (IJs) to soil desiccation and soil rehydration. The capacity to infect larvae of Galleria mellonella was used to assess the viability of EPNs after their exposure to desiccation. All the samples were initially hydrated to 10% moisture and moisture loss was recorded daily before rehydrating the soil. Desiccation tolerance results revealed that both species were able to withstand desiccated conditions or continuous dehydration for 20 days in sandy loam soil. H. bacteriophora caused 80% larval mortality after day 15 on rehydration of soil, whereas S. australe caused only 60% larval mortality. All the controls, with coarse river sand, gave zero larval mortality by day 21, indicating that the soil texture is also important for EPNs recovery from dehydrated soils. It may be concluded that coarse sand is not ideal for survival and effectiveness of EPNs, because of its incompetence to retain water.

Evaluation of Indigenous Entomopathogenic Nematodes as Potential Biocontrol Agents against Popillia japonica (Coleoptera: Scarabaeidae) in Northern Italy.

Simple SummaryThe Japanese beetle Popillia japonica is considered one of the most harmful organisms in the world for crops and the urban landscape. Popillia japonica spends most of its life cycle in the soil as a larva. At this stage, this beetle is more susceptible to biological control agents like entomopathogenic nematodes, which are obligate parasites of main soil-inhabiting insects, killing their host in just a few days. In 2014, P. japonica was detected in Northern Italy between the Piedmont and Lombardy regions. This research aims to investigate the natural occurrence of indigenous and locally adapted entomopathogenic nematodes along the Piedmont part of the Ticino river and test the most performing of them via bioassays. Natural isolates were recovered from 39 out of the 155 soil samples collected. The virulence of all entomopathogenic nematodes assessed by laboratory and semi-field assays highlighted that two isolates resulted in more efficiency in controlling P. japonica grubs. This result is very encouraging, and the use of these natural biocontrol agents against this pest is a fundamental component of eco-friendly management.The natural presence of entomopathogenic nematodes (EPNs) has been investigated in the Piedmont region (Northern Italy) in areas infested by the Japanese beetle Popillia japonica. Thirty-nine out of 155 soil samples (25.2%) were positive for EPNs. Most of the samples contained only steinermatids (92.3%), 5.1% contained heterorhabditids, and one sample (2.6%) contained both genera. All the recovered isolates were identified at species level both morphologically and molecularly. Steinernema carpocapsae was the most abundant and it was mainly distributed in open habitats, such as perennial meadows, uncultivated soils, and cropland, characterized by sandy loam soil texture and acidic pH. Steinernema feltiae has been found associated mainly with closed habitats such as coniferous and deciduous woodland, characterized by sandy loam-texture and extremely acidic soil. The three isolates of Heterorhabditis bacteriophora were collected only in open habitats (perennial meadows and uncultivated fields) characterized by strongly acidic soils with sandy loam texture. The virulence of all EPN natural strains was evaluated by laboratory assays against P. japonica third-instar larvae collected during two different periods of the year (spring, autumn). The results showed that larval mortality was higher for pre-wintering larvae than post-wintering ones. The five more promising EPN isolates were tested in the semi-field assay in which H. bacteriophora natural strains have been shown to be more efficient in controlling P. japonica grubs. All of these results are finally discussed considering the use of these natural EPNs as biological control agents against P. japonica, within an eco-friendly perspective of management.

Morphological and molecular characterization of Heterorhabditis bacteriophora isolated from Indian soils and their biocontrol potential.

Agricultural soils and open fields from Western Uttar Pradesh (India) were surveyed to determine the presence of entomopathogenic nematodes. From the entomopathogenic nematodes isolated, Heterorhabditis isolates were selected and further characterized using morphological, morphometrical and molecular approaches. The results showed that three isolated nematodes were Heterorhabditis bacteriophora and were associated with Photorhabdus laumondii subsp. clarkei bacteria, while the rests were identified as Heterorhabditis indica. The biocontrol potential of H. bacteriophora against three agricultural pests was evaluated. Nematode infectivity experiments showed that the nematode isolates DH7 and DH8 were highly pathogenic against cotton bollworm (Helicoverpa armigera) and tobacco cutworm (Spodoptera litura), and less pathogenic against white grub (Holotrichia serrata) larvae. This study sets the basis for establishing new biocontrol agents to be used in pest management programs in India.

Impact of entomopathogenic nematodes on Africanized honey bees Apis mellifera L. (Hymenoptera: Apidae) workers

Africanized honey bee populations (Apis mellifera L.) have been decreasing mainly due to the intense use of synthetic insecticides associated with pollution and climate change. To minimize these impacts on the environment and bee populations, the use of biological control agents has been intensified. These products are generally safer for non-target insects, such as bees, which are important pollinating insects. Thus, the objective of this study was to evaluate the impact of entomopathogenic nematodes on the longevity of the Africanized honey bee A. mellifera workers. Seven treatments were used: Heterorhabditis amazonensis, Heterorhabditis bacteriophora, Heterorhabditis indica, Steinernema carpocapsae, Steinernema feltiae, and Steinernema rarum, at a concentration of 40 infective juveniles per cm2 (IJs/cm²), and a control in which autoclaved distilled water was used. Two bioassays were performed: 1) spraying nematodes on the workers and 2) spraying nematodes on glass plates, in which the bees remained for two hours. Each treatment consisted of five replicates with 20 bees each. Bees were kept in cages of PVC (20 × 10 cm) covered with a voile fabric and provided pieces of cotton soaked in water and Candy paste. The cages were kept in a climatized room (27 ± 2 °C temperature, 60 ± 10% relative humidity, and 12 h photophase) and the mortality was evaluated from 12 to 240 hours. In bioassay 1, the three treatments with nematodes of the genus Steinernema reduced the longevity of the workers (103.9, 96.3, and 99.6 h) when compared to treatments with Heterorhabditis (149.7, 126.8, and 134.7 h), of which, only H. amazonensis (149.7 h) did not differ from the control (166.0 h). In bioassay 2, all treatments reduced the longevity of honey bees (155.4 to 93.9 h) in relation to the control (176.1 h). Entomopathogenic nematodes, especially Heterorhabditis, need to be tested using other methodologies and for different durations of exposure and application because in the laboratory, they were less selective to A. mellifera.

The influence of citrus orchard age on the ecology of entomopathogenic fungi and nematodes

ABSTRACT A three-year survey of the ecology of entomopathogenic nematodes (EPN) and entomopathogenic fungi (EPF) was undertaken on soils from citrus orchards of different ages to determine the influence of orchard age on the ecology of entomopathogenic fungi and nematodes. The influence of mulch and irrigation method on the occurrence of EPN and EPF was also determined. Most of the isolates recovered (n = 810) were Beauveria sp. (87.88% of all isolates), followed by Metarhizium sp. (11.87% of all isolates). Only 0.24% of soil samples collected during this study tested positive for EPN. All EPN isolates recovered were Heterorhabditis bacteriophora. No significant differences in EPF occurrence were recorded between orchards under drip and micro-sprinkler irrigation. EPF occurrence was significantly lower (P = 0.016) in orchards covered by mulch (31.85% ± 2.07% occurrence) than in orchards with no covering (38.57% ± 1.57% occurrence). EPF occurrence of 40.33 ± 2.13% was highest in non-bearing orchards, followed by mature orchards (nine years or older) (36.76 ± 2.05% of samples) with the lowest EPF occurrence of 25.30 ± 2.02% reported in juvenile orchards (four to eight years old). Juvenile orchards sustain significantly less EPF than mature and non-bearing orchards because of the combined negative impact of less favourable environmental conditions (lower shade density) and fungicide applications.

Efficacy of entomopathogenic nematode and Bacillus thuringiensis combinations against Holotrichia parallela (Coleoptera: Scarabaeidae) larvae

The larvae of Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae) are notorious soil insect pests that cause severe damage to crop production in China. However, the long-term use of insecticides seriously pollutes the environment and threatens human health. Therefore, an environmentally friendly, alternative control method to insecticides is crucial to effectively control these pests. In this study, we assessed the efficacies of possible combinations of entomopathogenic nematodes (EPNs), the Heterorhabditis beicherriana LF strain and Bacillus thuringiensis (Bt) strain HBF-18 to control H. parallela larvae under laboratory and field conditions. In the laboratory, the newly identified H. beicherriana LF strain showed higher pathogenicity than Heterorhabditis bacteriophora H06, Steinernema carpocapsae ALL and Steinernema carpocapsae SF-SN against H. parallela second instar larvae. The H. beicherriana LF strain exhibited a strong potential to control H. parallela larvae at an optimum temperature of 25 °C and soil moisture of 18%. The H. beicherriana LF strain was compatible with Bt (HBF-18). All EPN-Bt combinations caused significantly higher corrected mortality of H. parallela larvae than nematodes were applied alone after 7 and 11 days; in particular, a stronger synergistic effect was detected when Bt (HBF-18) at LC50 concentrations (0.79 × 107 CFU/g of soil) were combined with EPNs. In the peanut field experiment, synergistic interactions were observed for the combinations of the H. beicherriana LF strain (1 × 103 IJs/plant) and Bt (HBF-18) (1.14 × 1010 CFU/plant) against H. parallela third instar larvae, resulting in a sizable white grub reduction of 83.9 ± 0.82%. Our findings suggested that combining the H. beicherriana LF strain and Bt (HBF-18) is a recommended and practical strategy to manage pests in crop production systems.

Evaluación en casa malla del efecto de cuatro productos biológicos para el combate de jobotos (Phyllophaga sp)

El experimento se desarrolló en casa malla y se evaluó el efecto y la dosis de cuatro productos biológicos y uno químico utilizados en el control de larvas de jobotos (Phyllophaga sp.). El experimento se desarrolló en Guadalupe de Cartago, ubicado en las siguientes coordenadas geográficas: Latitud: 9.861884 y Longitud:-83.939692, a 1400 msnm. El tipo de investigación fue cuantitativa con un diseño del experimento de bloques completos al azar, con el uso de dos dosis y cinco tratamientos con tres repeticiones y cada repetición con diez unidades experimentales. Los productos biológicos utilizados fueron: Mycotrol® 11 EW (Beauveria bassiana, cepa GHA), Botani Gard® 50 WP (Beauveria bassiana, cepa GHA), Agro Gold® (nueve cepas de Bacillus spp), B-Green® (entomonemátodo, Heterorhabditis bacteriophora) y un producto químico comercial recomendado para control de jobotos. Para el control biológico de Phyllophaga sp., se determinó que Mycotrol® 11EW, fue el producto para el cual una dosis de 2.25cc/litro de agua proporcionó los mejores resultados. Para los otros dos productos que tuvieron efecto sobre el combate de Phyllophaga sp., el Agro Gold® y B- Green®, se determinó que la dosis utilizada en ambos casos no fue significativa, ya que se obtuvo valores de p iguales a 0.113 y 0.807, respectivamente. Lo que sí tuvo significancia fue realizar dos aplicaciones con frecuencia de una semana entre ellas con estos dos productos. Con los productos restantes, T2 Botani Gard® 50 WP (Beauveria bassiana, cepa GHA) y T5 (producto químico comercial), no hubo significancia estadística en su resultado ya que el valor de p para T2 con el factor dosis fue de 0.573 y con el factor aplicación fue 0.094. Para T5 el valor de p con el factor dosis fue 0.260 y para el factor aplicación fue 0.277.

Entomopathogens from Agricultural Soil and Their Potential to Control the Banded Fruit Weevil, Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae)

The banded fruit weevil (BFW), Phlyctinus callosus (Coleoptera: Curculionidae), is a major indigenous pest of deciduous fruits and grapevine in the Western Cape province of South Africa. Entomopathogens are effective in controlling soil-borne and above-ground stages of insect pests. Soil samples were collected from deciduous fruit orchards and vineyards in the Western Cape, baited with mealworms to isolate entomopathogenic nematodes (EPNs) and entomopathogenic fungi (EPF), which were identified using molecular techniques and assessed for their potential as biocontrol agents of BFW adults. A correlation analysis was performed to determine the effect of soil parameters on the presence of the entomopathogens. EPNs were trapped in 12 (17 %) samples, while Heterorhabditis bacteriophora and Heterorhabditis safricana were the only two species isolated. EPF were isolated from 26 (37 %) samples baited, with 14 fungal isolates identified as Beauveria bassiana (Cordycipitaceae) and 12 identified as Metarhizium anisopliae (Clavicipitaceae) complex. Heterorhabditis bacteriophora (53 %) gave significantly higher (P < 0.05) control of adult BFW than H. safricana (37 %). Metarhizium anisopliae (79 %) gave significantly higher (P < 0.05) control of BFW adults than B. bassiana (63 %). Organic matter, magnesium and phosphorus had a negative relationship with the occurrence of EPNs. A negative relationship was also reported between the occurrence of EPF, and organic matter and potassium. The results indicated that soils from the deciduous fruit orchards and vineyards from the Western Cape contain both EPNs and EPF with potential to be used in an integrated pest management system against soil-borne and above-ground stages of BFW.

Evaluation of three entomopathogenic nematode species against nymphs and adults of the sycamore lace bug, Corythucha ciliata

The sycamore lace bug Corythucha ciliata (Say) (Hemiptera: Tingidae) is an invasive species native to North America that has been introduced in Europe and infests various species of the ornamental plane trees (Platanus sp.). This study aims to test the susceptibility of C. ciliata nymphs and adults to different doses of three entomopathogenic nematode species under laboratory conditions. Heterorhabditis bacteriophora did not infect C. ciliata nymphs, while Steinernema carpocapsae exhibited higher virulence (77–96% at 132 IJs cm−2) to all stages of C. ciliata than S. feltiae (10–39% at 132 IJs cm−2). Steinernema carpocapsae was significantly more virulent at the highest dose (132 IJs cm−2) than at the medium (50 IJs cm−2) and lowest (25 IJs cm−2) doses. After 6 h and 12 h of nymph exposure to S. carpocapsae, this nematode caused 39% and 47% mortality at 132 IJs cm−2, respectively. The virulence of S. carpocapsae was significantly lower at 15 °C than at 25 °C (75.5% and 96% adult mortality, respectively) but was still more virulent than S. feltiae at both temperatures (29.5% and 39% adult mortality, respectively). These results show that S. carpocapsae could constitute a viable biological control agent for C. ciliata.

Effect of Cannabis sativa L. root, leaf and inflorescence ethanol extracts on the chemotrophic response of entomopathogenic nematodes

Soils represent the natural habitat of entomopathogenic nematodes (EPNs). When moving in soil, EPNs are oriented to follow a chemical signal (chemotaxis). Cannabis sativa L. is known to secrete a very wide spectrum of secondary metabolites. Ethanol extracts (EE) of different C. sativa L. organs were used to study the effect on EPN chemotaxis. The root, leaf and inflorescence EE of two hemp varieties and two medical cannabis breeding lines were used in laboratory chemotaxis assays with three EPN species (Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora) at 20 and 25 °C. The content of terpenes and cannabinoids in C. sativa L. inflorescences was measured as well. Overall, EPNs were most attracted or repelled by inflorescence extracts, followed by leaves and roots. The most abundant terpene in hemp inflorescences was trans caryophyllene (38.2% on average), the highest contents of total cannabidiol, total cannabigerol and total tetrahydrocannabinol were 9.65%, 0.89% and 0.62%, respectively. The attraction effect of S. sativa L. EE is a highly interesting outcome and could lead to the development of attractant compounds in EPN biological control. Cannabinoids and terpenes may be responsible for pronounced effects on EPN chemotaxis.