Bacteriophora HP88 Research Articles

Metabolic disruptions in Biomphalaria glabrata induced by Heterorhabditis bacteriophora HP88: Implications for entomopathogenic nematodes in biological control

Research on the use of entomopathogenic nematodes (EPNs) as a potential tool for the biological control of invertebrates has been growing in recent years, including studies involving snails with One Health importance. In this study, the effect of exposure time (24 or 48 h) of Heterorhabditis bacteriophora HP88 on the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentration of total proteins, uric acid, and urea in the hemolymph of Biomphalaria glabrata, were investigated. The concentrations of these metabolic markers were measured weekly until the end of the third week after exposure. Along with a significant reduction in total protein levels, a significant increase (p < 0.01) in uric acid and urea contents in the hemolymph of B. glabrata exposed to H. bacteriophora was observed. The accumulation of urea in these mollusks could lead to deleterious effects due to its high toxicity, inducing significant cell damage. Variations in transaminase activities were also observed, with snails exposed to EPNs showing significantly higher values (p < 0.01) than individuals in the control group, both for ALT and AST. These results indicate that experimental exposure to infective juveniles of H. bacteriophora causes significant alterations in the metabolic pattern of B. glabrata, compromising the maintenance of its homeostasis. Finally, exposure for 48 h caused more damage to the planorbid in question compared to snails exposed for 24 h, suggesting that the exposure time may influence the intensity of the host's response.

Evaluation of the efficiency of entomopathogenic nematodes exposed to different temperatures of vinasse in the control of Stomoxys calcitrans (Linnaeus, 1758) (Diptera: Muscidae).

The sugarcane industry generates byproducts that contribute to the proliferation of Stomoxys calcitrans. An analysis was carried out to verify the efficacy of Heterorhabditis bacteriophora HP88 and H. baujardi LPP7 at different vinasse temperatures to control S. calcitrans larvae. Ten fly larvae were deposited in plastic containers containing four mL of 50% vinasse. Each treatment consisted of 300 EPN/larvae of H. bacteriophora added to the containers and heated at temperatures of 25, 28, 31, 34, 37 and 40 °C. The same treatments were performed using H. baujardi. The treatments were carried out in a BOD incubator at 25 ± 1 °C and 70 ± 10% RH, and each treatment was replicated six times. The treated groups, controls and temperatures showed no statistical differences in terms of larval mortality rate (P=0.8573), percentage of dead pupae (P=0.1782) and adult emergence (P=0.4386). Larval mortality rates of 30% and 14.17% were achieved with H. bacteriophora and H. baujardi, respectively, while the control groups presented 3.89% with H. bacteriophora and 8.61% with H. baujardi. From the standpoint of temperatures, significant differences were found only at 37 and 40 °C for H. baujardi. The highest pupal mortality achieved with H. bacteriophora was 34.17% at 31 °C, while that reached with H. baujardi at 37 °C was 40%. The groups containing H. bacteriophora caused lower adult emergence rates at temperatures of 25, 28, 31 and 34 °C, while H. baujardi caused its lowest emergence rates at 37 and 40 °C. It is concluded that infection occurs in the immature stages of S. calcitrans by EPN when added to 50% vinasse solution at different temperatures and that nematodes caused negative effects on the emergence of fly larvae at varying temperatures.

Alterations in the metabolism of Pseudosuccinea columella (Mollusca: Gastropoda) caused by Heterorhabditis bacteriophora HP88 (Rhabditida: Heterorhabditidae)

The gastropod Pseudosuccinea columella participates in the dissemination of Fasciola hepatica in the environment, acting as the main intermediate host of this parasite in Brazil. The present study sought to elucidate the possible pathogenic effects of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora on P. columella, by evaluating the influence of infection on alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentrations of total protein, uric acid, and urea in the snail's hemolymph. For this, the snails were exposed to EPNs for 24 and 48 h, and for each exposure time, 20 snails were dissected after 7, 14 and 21 days for hemolymph collection. The primary findings suggest a significant proteolysis alongside elevated levels of uric acid and urea in P. columella infected individuals. These findings reveal that H. bacteriophora HP88 infection induced serious changes in the snail's metabolism, triggering important deleterious effects.

Effect of entomopathogenic nematodes Steinernema species (steinernematidae: rhabditida) and Heterorhabditis bacteriophora (heterorhabditidae: rhabditida) on the digestive enzymes and midgut histology of the African migratory locust Locusta migratoria migratorioides (acrididae: orthoptera)

In some governorates of Egypt, the African migratory locust L. migratoria migratorioides is in a gregarious phase. Swarm development was successfully prevented by biological control agents. In this work, the two entomopathogenic nematode species, Steinernema sp. (SII)and Heterorhabditis bacteriophora (HP88) were investigated as natural enemies against the fifth nymph and adult African locusts at various concentrations (300, 600, 900, 1200, and 1500 Infected juveniles/100 g. soil). To ascertain fatal activity at 25 °C, the nematode-inoculated sand method was used. The two nematode species were semi-field administered against fifth nymphs and adult stages at (25 ± 2 °C) and 55–60% relative humidity with concentrations (3000, 6000, 9000, 12000, and 15000 Infected juveniles/kg. soil). Protease, amylase, invertase, and trehalase levels in the digestive enzymes of both fifth nymphs and adults fed with LC50 of both nematodes significantly decreased, but lipase and chitinase levels significantly increased. Adult locusts treated with the LC50 of S. sp. SII had basophilic epithelial cells, severe lumen hemorrhage, and highly aberrant proliferating cytoplasm, whereas the LC50 of H. bacteriophora HP88 displayed necrosis in an epithelial cell with vacuoles, loss of nucleus, and loss of goblet cells.

Evaluation of the effect of Heterorhabditis bacteriophora (HP88) on Stomoxys calcitrans (Linnaeus, 1758) larvae (Diptera: Muscidae) in sugarcane bagasse ash.

The purpose of this study was to evaluate the effect of the EPN Heterorhabditis bacteriophora HP88 on Stmoxys. calcitrans larvae in sugarcane bagasse ash. Groups of 10 stable fly larvae were placed in Petri dishes containing filter paper and bagasse ash. Concentrations of 50, 150 and 250 EPNs/larva of S. calcitrans in four milliliters of distilled water were added to each plate. In the control group contained only distilled water, without EPNs. The bioassay had three replications and was maintained at 27 ± 1°C and 70-80% relative humidity. It was observed that mortality rate in all treated groups was significantly higher than in the control group (26,6%). The mortality rate in the presence of 50 EPNs/larva (46,6%) was lower than in 150 EPNs/larva (76,3%), which in turn was lower than 250 EPNs/larva group (93,3%). It was verified by analysis of variance and regression that there was a linear pattern of mortality, that is, the higher the EPNs/larva concentration, the higher the larval mortality. It was concluded that EPN H. bacteriophora HP88 was capable of infecting and causing mortality of stable fly larvae in sugarcane bagasse ash.

Evaluation in vitro of the virulence of two entomopathogenic heterorhabditid nematodes in the control of Stomoxys calcitrans (Diptera: Muscidae) larvae in byproducts of the sugar and alcohol industry.

Stomoxys calcitrans causes losses to livestock, mainly to cattle. This study aimed to determine the pathogenic potential of Heterorhabditis bacteriophora HP88 and H. baujardi LPP7 against S. calcitrans larvae after being exposed to byproducts of the sugar and alcohol industry. The efficacy of EPNs on stable fly larvae was evaluated in bioassays with vinasse at three temperatures (16, 25 and 35 °C) and concentrations (0, 50 and 100%), as well as in relation to larva age (4, 6 and 8 days) in filter cake and EPNs concentration (100, 300 and 500 IJs/larva) in sugarcane bagasse. H. bacteriophora showed higher efficacy than H. baujardi at all temperatures. Vinasse did not have a negative effect on the virulence of H. bacteriophora. The age of fly larvae did not affect the mortality rates caused by the EPNs. In bagasse, H. bacteriophora presented higher mortality rates than the control group. It is concluded that EPNs can be a potential component in integrated strategies of stable fly control and outbreak prevention in areas of sugar and alcohol production.

Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae), isolate HP88, induces reproductive and physiological alterations in Biomphalaria glabrata (Gastropoda: Planorbidae): an alternative for biological control of schistosomiasis

Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) that is mutually associated with Photorhabdus luminescens, utilized globally for biological control of numerous organisms. Freshwater snails of the species Biomphalaria glabrata have been incriminated as the main intermediate hosts of Schistosoma mansoni in Brazil, but virtually nothing is known about the susceptibility of these gastropod to EPNs. Information in this respect is relevant for control of these intermediate hosts, and thus of the helminthiases they transmit. This paper for the first time reports the susceptibility of B. glabrata to infective juveniles of H. bacteriophora (isolate HP88) under laboratory conditions. For that purpose, six groups were formed: three Control groups (not exposed) and three Treated groups, in which the snails were exposed to 300 juveniles infecting the nematode over three weeks. The entire experiment was conducted in triplicate, using a total of 270 snails. Significant physiological alterations in B. glabrata were observed in response to the infection by H. bacteriophora HP88, characterized by decreased levels of hemolymphatic glucose as well as reduced contents of glycogen stored in the host's digestive gland. In parallel, the hemolymphatic activity of lactate dehydrogenase increased in the infected snails, indicating that the infection induces breakdown of carbohydrate homeostasis in B. glabrata. Additionally, all the reproductive parameters analyzed were reduced as a consequence of the infection. The results indicate the occurrence of the phenomenon of parasitic castration in the B. glabrata/H. bacteriophora HP88 interface, probably due to the depletion of galactogen in the parasitized organism. Although the infection did not cause lethality in the population of infected snails, H. bacteriophora HP88 compromised the reproductive performance of B. glabrata, suggesting its applicability in programs for biological control of this planorbid.

Development of the soil-inhabiting stages of Ceratitis capitata infected with entomopathogenic nematodes: insights on survival

ABSTRACT The Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is a major pest that affects fruit production worldwide. This insect spends part of its life cycle in the soil, making it a target for entomopathogenic nematodes (EPNs). Laboratory assays were conducted to assess the development of the soil-inhabiting stages (third-instar larvae, prepupae, and pupae), in terms of survival, infected with the EPN strains Steinernema carpocapsae (Weiser) All, Steinernema riobrave Cabanillas, Poinar & Raulston ML29, Heterorhabditis bacteriophora (Poinar) HP88, and H. bacteriophora AS1. Treatment with the native strain (H. bacteriophora AS1) caused the highest mortality compared to the remaining exotic strains. Mortality of the third-instar larvae in the sand proportionally increased to the nematode density (infective juveniles per cm2). Of the tested stages, larvae were the most susceptible stage. Young pupae (1-day-old) were more susceptible to all nematode strains than older pupae (9-day-old). Development, in terms of survival, is a good criterion to evaluate the potential of EPNs to monitor C. capitata.

Infection and reinfection of Stomoxys calcitrans larvae (Diptera: Muscidae) by entomopathogenic nematodes in different times of exposure.

Stomoxys calcitrans is a hematophagous dipteran. Several agents are used in biological control, including entomopathogenic nematodes (EPNs). Bioassay I involved an evaluation of the effect of Heterorhabditis bacteriophora HP88 and Heterorhabditis baujardi LPP7 on S. calcitrans larvae in different periods of exposure. Groups of 10 larvae were placed in Petri dishes and 200 EPNs/larva were added, which were divided into groups according to the exposure times of 2, 4, 6, 12, 24 and 48 hours. The purpose of Bioassay II was to evaluate the efficacy of the EPNs in infecting S. calcitrans larvae when they were isolated from stable fly larvae in Bioassay I. Groups of 10 larvae were placed in Petri dishes and 200 EPNs/larva were added. In bioassay I, H. bacteriophora caused mortality rates of 51.7, 83.3 and 91.7% in 12, 24 and 48 hours, respectively, while H. baujardi caused mortality rates of 9.3 (12h), 35 (24h) and 35% (48h). In Bioassay II, H. bacteriophora and H. baujardi resulted in mortality rates of 35% and 25%, respectively. It was concluded that the longest exposure times presented the highest larval mortality and that EPNs isolated from S. calcitrans are not efficient in controlling the larvae fly.

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.

Efficacy of entomopathogenic nematodes in insect cadaver formulation against engorged females of Rhipicephalus microplus (Acari: Ixodidae) in semi-field conditions

The present study evaluated, in the laboratory, the virulence of Heterorhabditis bacteriophora LPP30 against engorged females of Rhipicephalus microplus; in addition, we evaluated, in semi-field tests, the effects of four isolates of Heterorhabditis spp. (i.e., H. bacteriophora HP88, Heterorhabditis baujardi LPP7, Heterorhabditis indica LPP1 and H. bacteriophora LPP30) in insect cadaver formulation against the non-parasitic phase of R. microplus. In the first experiment (in vitro), engorged females were exposed, in Petri dish, to H. bacteriophora LPP30 at 75, 150, 300, 600, 1200 and 2400 nematodes/tick (10 ticks per concentration tested). In the second experiment (semi-field), five engorged females and four cadavers of Galleria mellonella infected with nematodes were placed in pots with soil and grown Brachiaria decumbens; the pots were hold outdoor, exposed to natural environment conditions during the tests. In the third experiment (semi-field), 65 days after the cadavers had been placed in the pots for the second experiment, new engorged females (five per pot) were placed in the pots of the groups treated with H. bacteriophora HP88 or H. baujardi LPP7, to assess their persistence in the soil. In the first test, the percent control was higher than 95% in all treatment groups. In the second experiment, at day 22, the mean mortality rate was 78% in the groups treated with H. bacteriophora LPP30 or H. indica LPP1, and reached 100% and 98% when treated with H. bacteriophora HP88 and H. baujardi LPP7, respectively. In this experiment, the egg-laying inhibition index was higher than 90% in the groups treated with H. bacteriophora HP88 (97.2%) or H. baujardi LPP7 (91.9%). In the third experiment with H. bacteriophora HP88 and H. baujardi LPP7, the egg-laying inhibition index was 59.1% and 43.1%, respectively. We concluded that the isolate LPP30 was highly virulent under laboratory conditions, whereas in semi-field tests, HP88 and LPP7 were the most effective isolates. Moreover, HP88 and LPP7 remained active against engorged females of R. microplus in the soil for 65 days after application of EPN-infected cadavers of G. mellonella.

Potential of entomopathogenic nematodes of the genus Heterorhabditis for the control of Stomoxys calcitrans (Diptera: Muscidae).

The present study verified the pathogenic potential of entomopathogenic nematodes (EPNs) of the genus Heterorhabditis (Heterorhabditis bacteriophora, isolate HP88 and Heterorhabditis baujardi isolate LPP7) to immature stages of Stomoxys calcitrans in the laboratory. All EPN concentrations of the H. bacteriophora HP88 strain caused mean larval mortality greater than 90% after four days. Higher concentrations of the H. baujardi LPP7 isolate (≥50 EPNs/larva) eliminated more than 70% of larvae after six days with the concentration 200 EPNs/larva reaching mortality levels of 93.3%. The larval mortality at all concentrations of EPNs (25, 50, 100, 150, and 200 EPNs/larva) for both strains was significant (p<0.05) when compared to the respective control groups. Concentrations of H. bacteriophora HP88 yielded an LC50 of 0.36 EPN/larva and LC90 of 29.1; while H. baujardi LPP7 yielded an LC50 of 39.85 and LC90 of 239.18. H. bacteriophora HP88 provided greater inhibition of the emergence of adults when compared to the response obtained with H. baujardi LPP7. EPNs did not cause considerable mortality when applied directly to pupae. The set of observed results suggests that the EPNs of the genus Heterorhabditis, isolates HP88 and LPP7, are a promising alternative in the control of the stable fly.

VIRULENCE OF ENTOMOPATHGENIC NEMATODES AGAINST THE INTERMEDIATE HOST OF FASCIOLA SPP., LYMNAEA NATALENSIS KRAUSS.

Pathogenicity of entomopathogenic nematodes (EPNs) Steinernema carpocapsae DD136 (Weiser), Heterorhabditis indica RM1 and H. bacteriophora HP88 were applied under laboratory conditions. On the fresh water snails, Lymnia natalensis Krauss observation recorded high mortality percentage in infected snails with EPNs. Also, there was a positive correlation between time exposure increase and mortality percentage. Results indicated that EPNs may play an important role as biocontrol agents in integrated pest management (IPM) against L. natalensis.

Molecular identification and genetic diversity among Photorhabdus and Xenorhabdus isolates

Five bacterial strains were isolated from the hemocoel of the greater wax moth larvae (Galleria mellonella) infected with the entomopathogenic nematodes: Heterorhabditis bacteriophora HP88, Heterorhabditis indicus RM1 and Heterorhabditis sp (S1), Steinernema abbasi and Steinernema sp. (S II). Strains were identified as Photorhabdus luminescens HRM1, P. luminescens HS1, P. luminescens HP88, Xenorhabdus indica and X. nematophila ATTC19061 using 16S rDNA sequence analysis. To reveal the genetic diversity among these strains, three molecular markers (RAPD, ISSR and SRAP) were employed. RAPD analysis showed 73.8 and 54.5 polymorphism percentages for the Photorhabdus and Xenorhabdus strains, respectively. ISSR analysis resulted in 70.1 and 75.2 polymorphism percentages among the Photorhabdus and Xenorhabdus strains, respectively. The SRAP analysis indicated that 75.6 and 61.2% genetic polymorphism was detected among Photorhabdus and Xenorhabdus strains, respectively. The cluster analysis grouped the three Photorhabdus strains together in one cluster and the two Xenorhabdus strains together in another cluster indicating the phylogenetic relationships among them. The genotype-specific markers detected from the three molecular markers (RAPD, ISSR and SRAP) were sufficient to distinguish between the different bacterial strains tested and can be used in the future IBM program that could be built on the use of these strains.

Infectivity of Four Entomopathogenic Nematodes in Relation to Environmental Factors and Their Effects on the Biochemistry of the Medfly Ceratitis capitata (Wied.) (Diptera: Tephritidae).

Late third instars of the medfly, Ceratitis capitata (Wied.), migrate from the host fruit into the soil and leaf litter beneath host trees, where they may become a target for entomopathogenic nematodes (EPNs). The effects of ultraviolet (UV) light, temperature, soil type (texture), and soil moisture level on infectivity of the four tested EPNs Heterorhabditis bacteriophora AS1, H. bacteriophora HP88, Steinernema carpocapsae ALL, and Steinernema riobrave ML29 to late third instars of C. capitata were evaluated. Biochemical alterations induced by the most virulent nematodes were quantified. The nematode infectivity decreased with increase in exposure time to UV light, whereas it increased with increase in temperature. Infectivity increased in sandy soil, whereas it decreased in silt and clay soils. Soils with high moisture levels decreased infectivity. Based on the 50% lethal concentration (LC50), H. bacteriophora AS1 and S. carpocapsae ALL were the most virulent heterorhabditid and steinernematid nematodes, respectively, with the highest virulence for H. bacteriophora AS1. The nematodes caused significant decline in total protein and cholesterol content of larvae and caused reduced activity of transaminases and phosphatases. In contrast, they significantly enhanced total glucose content. It can be concluded that the most optimum environmental conditions of the tested nematodes to elicit their infectivity against late third instars of C. capitata were sandy soil with 10% moisture level, ambient temperature of 25°C, and no exposure to UV. The EPNs tested can affect late third instars of C. capitata by targeting different biochemical molecules in different metabolic pathways. The interaction between them and the host larvae appears to be primarily nutritional.

Entomopathogenic nematodes in insect cadaver formulations for the control of Rhipicephalus microplus (Acari: Ixodidae)

This study evaluated the efficacy of four entomopathogenic nematode (EPN) strains in insect cadaver formulations against Rhipicephalus microplus and compared the efficacy of the most virulent EPNs applied in cadavers of Galleria mellonella and Tenebrio molitor. In the first experiment, infected G. mellonela larvae were used as the source of EPNs. Engorged females of R. microplus were placed in pots filled with soil and different numbers of G. mellonella larvae infected with one of four species of nematodes. All treatments with EPNs of the genus Heterorhabditis caused significant reduction (p<0.05) in the egg mass weight and hatching percentage of larvae. The EPNs of the genus Steinernema, except for the group exposed to Steinernema carpocapsae ALL, whose source nematodes included six larvae of G. mellonella, caused a significant reduction (p<0.05) in the egg mass weight produced per female. Steinernema feltiae SN applied with two, four, and six cadavers and S. carpocapsae ALL with two cadavers caused a reduction in hatching percentage of larvae of R. microplus (p<0.05). The percentage of control was above 95% in all groups treated with Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 and in the treatment with four larvae infected with S. feltiae SN. The second experiment followed the same methodology, using G. mellonella and T. molitor larvae infected by the two most virulent EPNs. H. bacteriophora HP88 and H. indica LPP1 in different formulations caused reduction in the egg mass weight and hatching percentage of larvae. The percentage of control were 82.4 and 84.9% for H. bacteriophora HP88 and H. indica LPP1, respectively, formulated in T. molitor, and reaching 99.9% in groups formulated with G. mellonella. The EPNs tested in insect cadaver formulation showed pathogenicity to engorged females of R. microplus and EPNs of the genus Heterorhabditis formulated in G. mellonella larvae were more effective.

English

The virulence of new nine heterorhabditid isolates from South Carolina (Heterorhabditis megidis LEX, H. zealandica EDS and CHR, and H. bacteriophora WPS, SMP, PD, CFG, MF and CFM strains) against the beet armyworm was compared with two known heterorhabditid nematodes (H. bacteriophora Hb and HP88 strains) under laboratory conditions. The Petri-plate bioassay procedure was used to evaluate the susceptibility of the Spodoptera exigua larvae to the heterorhabditids at concentrations of 10, 25, 50, and 100 infective juveniles (IJs) per larva. Mortalities were counted for 4 days. At the final count, mortalities were 53.6-100, 72-100, 79.8-100, and 92.9-100% for all nematode species/strains at the concentrations of 10, 25, 50, and 100 IJs per larva, respectively. H. megidis LEX strain was superior and differed than others by having 100% mortality in all of the concentrations. It was second to cause early mortality. It had the highest mortality rate at 10 nematodes per larva and H. bacteriophora WPS, H. zealandica CHR, H. bacteriophora HP88 and H. zealandica EDS strains followed it with 92.9, 89.3, 85.7 and 82.1% mortality, respectively. LC50 for most of the nematodes was relatively low (10 IJs per larva).&nbsp; Virulence of H. bacteriophora WPS, HP88 and SMP and H. zealandica CHR strains were similar. The least virulent heterorhabditid was H. bacteriophora CFM strain with LC50 value of 14.8 IJs per larva. The LT50 value of H. bacteriophora WPS strain was the smallest and it was followed by H. megidis LEX, H. zealandica CHR and EDS, H. bacteriophora SMP, HP88, MF, PD, Hb, CFG and CFM strains, respectively. &nbsp; Key words: Biological control, entomopathogenic nematodes, Heterorhabditis, Spodoptera exigua.

First report of pathogenicity of entomopathogenic nematodes of the genus Heterorhabditis on partially engorged females of Dermacentor nitens (Acari: Ixodidae)

The aim of this study was to evaluate the effect of different concentrations of the entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 on the reproductive biology of partially engorged females of Dermacentor nitens. Four groups were formed, with each group containing 10 females and exposed to concentrations of 0, 75, 300, and 1200 nematodes for each female. This procedure was performed separately for each nematode. The following biological parameters were evaluated: egg mass weight, egg production index, hatching percentage, and percentage of control. H. bacteriophora HP88 at the two highest concentrations (300 and 1200 EPNs/female) caused a reduction (p<0.05) on the egg mass and egg production index. Was noted a significant reduction (p<0.05) in the percentage of hatched in all the treated groups. For H. indica LPP1, all treatments resulted in decreased (p<0.05) values for all the parameters. The percentages of controls obtained at concentrations of 75, 300, and 1200 EPNs/female were 56.3, 89.3, and 98.8 and 77.5, 77.1, and 95.9 for H. bacteriophora HP88 and H. indica LPP1, respectively. Therefore, it is concluded that these nematodes showed pathogenicity toward partially engorged females of D. nitens, thereby negatively affecting the reproductive biology of this tick.

Entomopathogenic nematodes associated with essential oil of Lippia sidoides for control of Rhipicephalus microplus (Acari: Ixodidae)

In vitro effect of the association of the entomopathogenic nematodes Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 with the essential oil of Lippia sidoides on engorged females of Rhipicephalus microplus was assessed. Engorged females with homogeneous weights (p >0.05) were divided into six groups of ten ticks each (each female = an experimental unit). In the treated groups, the ticks were exposed to the oil (40 μl/ml=4%) and nematodes (300 entomopathogenic nematodes (EPNs/tick) separately and also to the nematodes together with the oil, while in the control group, the females were immersed in Tween 80 (3%). All the treatments caused a significant reduction in the egg mass weight (p <0.05). The hatching percentage of larvae was reduced (p <0.05) in the groups treated with H. bacteriophora HP88, H. indica LPP1, and H. bacteriophora HP88 associated with the oil, but in the group treated only with the oil, the hatching of percentage of larvae rate was similar to that of the control group (p >0.05). The percentage of control in the group exposed only to the oil was 50.7%, while in the other treated groups, the percentage of control was greater than 95 %, reaching 100 %in the group treated with H. indica LPP1 associated with the oil. The results of the L. sidoides essential oil in the concentrations tested in association with both H. bacteriophora HP88 and H. indica LPP1 indicate that these combinations can be used to control R. microplus.

Association between entomopathogenic nematodes and fungi for control of Rhipicephalus microplus (Acari: Ixodidae)

The aim of the study was to assess the effect of the association of entomopathogenic nematodes and fungi on Rhipicephalus microplus. The nematodes used were Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 and the fungi were Metarhizium anisopliae IBCB 116 and Beauveria bassiana ESALQ 986. In the groups treated with the fungi, the females were immersed for 3 min in a conidial suspension, while in the groups treated with the nematodes, the ticks were exposed to infective juveniles. To evaluate the interaction between entomopathogens, the females were first immersed in a conidial suspension and then exposed to the nematodes. The egg mass weight and hatching percentage values of the groups treated with M. anisopliae IBCB 116 and B. bassiana ESALQ 986 in the two experiments were statistically similar (p > 0.05) to the values of the control group. In the groups treated only with nematodes, there was a significant reduction (p < 0.05) in the egg mass weight, a fact also observed for the hatching percentage of the group treated with H. indica LPP1. In all the groups treated with nematodes in association with fungi, there was a significant reduction (p < 0.05) in the egg mass weight and hatching percentage. The percentage of control of the groups treated with fungi alone varied from 31 to 55%. In the groups treated with nematodes associated or not with fungi, the control percentage was always greater than 90% and reached 100% in the group treated with H. bacteriophora HP88 associated with the fungus M. anisopliae IBCB 116.