HP88 Strain Research Articles

The Efficacy of Entomopathogenic Nematodes Plus an Adjuvant against Helicoverpa zea and Chrysodeixis includens in Aboveground Applications.

In the southern United States, corn earworm, Helicoverpa zea (Boddie), and soybean looper, Chrysodeixis includens (Walker) are economically important crop pests. Although Bt crops initially provided effective control of target pests such as H. zea, many insect pests have developed resistance to these Bt crops. Alternative approaches are needed, including biological control agents such as entomopathogenic nematodes (EPNs). However, the effectiveness of EPNs for aboveground applications can be limited due to issues such as desiccation and ultraviolet radiation. Effective adjuvants are needed to overcome these problems. Ten strains of EPNs were tested for virulence against eggs, first to fourth instars, fifth instars, and pupae of H. zea and C. includens in the laboratory. These 10 EPN strains were Heterorhabditis bacteriophora (HP88 and VS strains), H. floridensis (K22 strain), Hgkesha (Kesha strain), Steinernema carpocapsae (All and Cxrd strains), S. feltiae (SN strain), S. rarum (17c+e strain), and S. riobrave (355 and 7-12 strains). EPNs could infect eggs of H. zea or C. includens in the laboratory, but the infection was low. The mortality caused by 10 EPN strains in seven days was significantly higher for the first to fourth instars of H. zea compared to the control, as was the fifth instars of H. zea. Similarly, for the first to fourth and fifth instars of C. includens, the mortality was significantly higher compared to the controls, respectively. However, only S. riobrave (355) had significantly higher mortality than the control for the pupae of H. zea. For the pupae of C. includens, except for H. bacteriophora (HP88), S. rarum (17c+e), and H. floridensis (K22), the mortality of the other seven strains was significantly higher than the control. Subsequently, S. carpocapsae (All) and S. riobrave (7-12) were chosen for efficacy testing in the field with an adjuvant 0.066% Southern Ag Surfactant (SAg Surfactant). In field experiments, the SAg Surfactant treatment significantly increased the mortality and EPN infection for S. carpocapsae (All) on first instars of H. zea in corn plant whorls. On soybean plants, with the SAg Surfactant, S. carpocapsae (All) was more effective than S. riobrave (7-12) on fifth instars of C. includens. This study indicates that EPNs can control H. zea and C. includens, and SAg Surfactant can enhance EPN efficacy.

Compatibility of Native and Imported Entomopathogenic Nematodes with Different Applications of Insecticides for Controlling the Cigarette Beetle, Lasioderma serricorne Fabricius (Coleoptera: Anobiidae)

The cigarette beetle, Lasioderma serricorne Fabricius (Coleoptera: Anobiidae), is an important pest of stored products in the world which caused major economic losses that required many strategies for controlling insect pest. This study investigated native entomopathogenic nematodes (EPNs) and imported EPN species alone at different IJs concentrations or in combination with three application rates (recommended, quarter and half recommended concentrations) of lambda-cyhalothrin, emamectin benzoate and indoxacarb against the third and the fourth larval instars of its pest under laboratory conditions. The results showed that The native H.bacteriophora (Ar-4 strain) and the imported H.bacteriophora (HP88 strain) were more effective against the fourth larval instar of L. serricorne than the third instar followed by S.carpocapsae (All strain) while H.bacteriophora (Ba-1 strain) and S. feltiae strain were the least efficacy. According to LT50 of tested EPNs, 100 IJs/larva was the best concentration used against the larvae instars of L. serricorne. As well as, the fourth instar was more susceptible to the tested applications of pesticides than the third larval instar. Moreover, The application with a quarter recommended dose of indoxacarb was the most toxicity application against the fourth instar when compared to lambda-cyhalothrin andemamectin benzoate. On the other hand, the effects of the interactions between native and imported EPNs varied greatly as stated by application rates of tested insecticides and juveniles' concentration of EPNs. It is concluded that the best interaction effect was obtained with quarter recommended application (0.25 RC) of lambda-cyhalothrin when combined with EPNs at 100 IJs/larva, which displayed synergistic effect to overcome incompatibility particularly with heterorhabditid species, the effect that could be beneficial when making progress the integrated program for stored-product pests.

In Vitro Compatibility and Combined Efficacy of Entomopathogenic Nematodes with Abamectin and Imidacloprid Against the White Grub, Pentodon bispinosus Kust.

One of the challenges in mixing entomopathogenic nematodes (EPNs) with chemical control is low predictable compatible information; hence, pesticides are misused by farmers. Therefore, the study aimed to clarify the result of mixing abamectin and imidacloprid on the infectivity of EPNs against larvae of hard-black beetle Pentodon bispinosus Kust., besides, investigating the fluctuations of the joint action of EPN species and chemical pesticides during the study period. Recommended dose (RD) of imidacloprid (LT50= 5.20 and 14.20 d) was more efficient comparing with abamectin (LT50= 18.14 and 24.22 d) on the first third and instar larvae of white grubs. Heterorhabditis bacteriophora (Ar-4) showed the highest tolerance (LT50=10.11 and 6.22 d) while Steinernema feltiae (Filipjev) was the most sensitive (LT50=5.53 and 3.55 d) after exposure to abamectin and imidacloprid at RD, respectively. EPNs plus chemical insecticides combinations on first instar larvae recorded the higher median lethal concentration (LC50) except S. feltiae (Filipjev) plus abamectin and all combinations of EPNs with imidacloprid. All combinations with EPNs showed lower LC50 values than EPN alone except abamectin with some tested H. bacteriophora with III instar larvae. Based on LC50 values, all EPNs combinations with imidacloprid surpassed EPN alone or abamectin combinations. Moreover, mortality reached 100% in the 1st instar of white grubsat concentration 250 IJs/larva H. bacteriophora (HP88 strain) compared with 92% in the 3rd instar larvae at the same concentration after 4 weeks of incubation. The potentiation effect was observed after one week in the 3rd instar larvae only when abamectin combined with H. bacteriophora (Ar-4 strain) and S. carpocapsae (All strain) while after 3 weeks with 1st instar larvae in combination between S. feltiae (Filipjev) and the RD of abamectin and imidacloprid at concentration 150 IJs/larva. No synergistic interaction was observed in combinations of EPNs with neither abamectin nor imidacloprid. During mixing chemical pesticides and bioagents, the chemical pesticide is the independent variable effect on EPNs viability and infectivity which is affected by combining period and species. The final interaction mainly depends on the chemical pesticide selectivity and toxicity to target insects (stage and instar).

The Joint Action of Entomopathogenic Nematodes Mixtures and Chemical Pesticides on Controlling Helicoverpa armigera (Hübner)

Chemical pesticides are characterized by the rapid impact effect in reducing pest population, while, microbial pesticides need along the latent period to cause a limited reduction of the pest population. Low efficiency of biocides may be due to low compatibility with agrochemicals or poor application of biocide, so, the study carried out to evaluate the possibility of mixing five common chemical insecticides and nematicides with five compatible entomopathogenic nematodes (EPNs). For the control of tomato fruit borer (Helicoverpaarmigera),bioassay revealed that pesticide chlorpyrifos (Pestban 48% EC), chlorpyrifos (Tafaban 48% EC) and flubendiamide (Takumi 20% WG) were applied at the recommended dose. Flubendiamide was less toxic to EPNs infective juveniles compared to fenamiphos (Dento 40% EC). Moreover, steinernematid species were more sensitive than heterorhabditid species to pesticides recording 49.45% and 43.76%, respectively, after 7 days of exposure. The joint action of tested chemical pesticides with IJs of EPNs in controlling the 5th instar larvae of tomato fruit wormshowed an additive or antagonistic reaction with no evidence of synergistic action. Antagonism reaction was recorded with all fenamiphos combinations;the combination ofabamectin and S. feltiae as well as H. bacteriophora (Ba-1), in addition to, flubendiamide combinations with S. feltiae and H. bacteriophora (Ba-1). While, an additive effect was observed in flubendiamide combinations with S. glaseri, S. carpocapsae and H. bacteriophora (HP 88). In the greenhouse experiment, the application of EPNs alone caused mortality ranged from 28 to 36% for 5th instar larvae. Whereas, the highest larval mortality was observed in descending order for combinations between H. bacteriophora (HP88 strain) with fenamiphos (64.0%), chlorpyrifos (54%) and abamectin (54.0%), while, local isolate, H. bacteriophora (Ba-1 strain) achieved mortality ranged from 40 to 50 % with the tested pesticides. Overall, results indicate the feasibility of the integrated use of these nematode species and chemical pesticides in crop protection.

Joint Toxicity of Insecticides and some Entomopathogenic Nematode Species against Rhynchophorus ferrugineus (Olivier) Insect In Vitro

Efficacy of imported and local entomopathogenic nematodes (EPNs) alone or in combinations with the insecticides, imidacloprid, zeta-cypermethrin, profenfos and emmectin benzoate against red palm weevil (RPW), Rhynchophorus ferrugineus differed greatly according to nematode species and instar larvae under laboratory conditions.Both Heterorhabditis bacteriophora (HP88 strain) and local species H.bacteriophora (Ar-4 strain) showed promising results by killing 92.20 and 82.13 % of the 4th instar larvae after 9 days of exposure, respectively. Whereas, S. feltiae and H. bacteriophora (Ht strain) showed less insecticidal activity against 4th, 9th and 11th instar larvae. On the other hand, Egyptian H. bacteriophora (Ar-4 strain) was more effective than H.bacteriophora (Ht strain). Adults of R. ferrugineus were less susceptible to nematode infection than instar larvae. According to LD 50 with LT 50 values, H. bacteriophora (HP88 strain) was more aggressive killer to RPW than native strains and LT50 values were 5.693, 4.319 and 2.943 days at concentrations of 500, 1500 and 2500IJs/ml, respectively. At the LC50 and LC90 values, imidacloprid was the most toxic for 9th and 11th Instars of R. ferrugineus, whereas, profenfos was the least effective one after 24 hr of exposure. The joint action of chemical pesticides with IJs of EPNs in controlling the 9th and 11th instar larvae of R. ferrugineus showed an additive or potentiation reaction with no evidence of antagonistic action.Overall, results indicate the feasibility of an integrated use of these nematode species and chemical pesticides in controlling red palm weevil under field conditions.

Field Control of Synanthedon myopaeformis Borkh and Zeuzera pyrina L. Using Entomopathogenic Nematodes, Insecticides and Microbial Agents

Three field trials were carried out to evaluate the efficacy of two local strains of entomopathogenic nematode, Heterorhabditis bacteriophora ( Ar-4 and Ht strains) isolated from EL-Arish and Giza in Egypt and two commercially available nematode species, Steinernema carpocapsae (All strain) and H. bacteriophora (HP88 strain) for the control of fruit tree borers, Synanthedon myopaeformis and Zeuzera pyrina on apple trees. The entomopathogenic nematodes (EPNs) were used alone or combined with recommended dose of the microbial pesticide, Bacillus thuringiensis (Diple2X), and insecticides, diazinon and phenthoate. The obtained results showed that the combined EPNs with insecticides were more effective as injection technique than spray method. Mortality percentages of S. myopaeformis ranged between 47.61 to 88.88 % in the injection treatments while in the spraying one it ranged between 37.14 to 74.07 %. In comparison between the efficacy of native and imported entomopathogenic nematodes in controlling Z. pyrina using spray technique, percentage mortality resulted from the combination of native nematodes i.e. H.bacteriophora (Ht strain) and H. bacteriophora (Ar-4 strain) and insecticides either penthoate or diazinon reached 69.23; 64.00 and 22.72; 64.18%, respectively. Whereas, percentages mortality were 44.44; 50.00 and 52.94; 54.16% with S. carpocapsae (All strain) andH. bacteriophora (HP88 strain), respectively. The susceptibility of Z. pyrina to the nematode species differed greatly according to the nematode species used either alone or in combination with the recommended dose of B. thuringiensis. The entomopathogenic nematode H. bacteriophora (HP88 strain) was more virulent than S. carpocapsae (All strain) in controlling Z. pyrina with percentage mortality reached 77.5 and 62.1%, respectively

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 Entomopathogenic Nematodes Steinernema glaseri and Heterorhabditis bacteriophora Poinar (HP88 strain) Against the Black Cutworm, Agrotis ipsilon.

Virulence of entomopathogenic nematodes, Steinernema glaseri and Heterorhabditis bacteriophora Poinar (HP88 strain) were studied against 3rd, 4th, 5th and 6th instar larvae of the black cutworm, Agrotis ipsilon. The observed mortality caused by the both tested nematodes at different time intervals was recorded. The establishment of nematodes in a host depends greatly on its ability to manage host defences so, the host haemocyte interaction with entomopathogenic nematodes were observed by encapsulation, nodule formation and phagocytosis processes. Phagocytosis is known to stimulate production of lysosomal enzymes. Acid phosphatase acts as a lysosome marker so; the activity and the pattern of acid phosphatase during the course of infection were recorded. Also, total protein and protein pattern were screened. Results indicated that, the two nematodes had variable significantly effects. S. glaseri recorded a highly significantly affect than H. bacteriophora. In addition, there are relationship between mortality rate and time exposure of S. glaseri and H. bacteriophora against 3rd, 4th, 5th and 6th larval instars of A. ipsilon i.e. the time exposure increased the susceptibility also increased. At the lower concentration, fourth and/or fifth instars were the most susceptible instars to S. glaseri ,while the 3rd and 4th instar larvae were most vulnerable instars to the infection with H. bacteriophora. Results was recorded that, six haemocyte types were identified in A. ipsilon 6th instar larvae: prohaemocytes, plasmatocytes, granulocytes, spherulocytes, oenocytoids, and adipohaemocytes. S. glaseri in A. ipsilon escape encapsulation and overcome host immunity faster than H. bacteriophora which recognized by host haemocytes. Prohemocytes, plasmatocytes or granulocytes are phagocytic cells in A. ipsilon 6th instar larvae. Phagocytosis was expressed in A. ipsilon haemocytes infected with H. bacteriophora at a higher rate compared with S. glaseriinfection. Data demonstrated both S. glaseri and H. bacteriophora induced a significant decrease in total protein contents after 24hrs from infection. While, there was significant increase in acid phosphatase activity after 6 hrs of infected groups of S. glaseri and H. bacteriophora. This increase may be due to phagocytosis processes which recorded in the present study at this time because phagocytosis is known to stimulate production of lysosomal enzymes. There is an acid phosphatise band detected only in H. bacteriophora and S. glaseri samples with Rf 0.86 after 6 and 12hrs from infection. This band may refer to nematodes exudates which contain high amount of this enzyme that the nematodes can easily penetrate and digest host tissues. There is a characterestic band of S. glaseri protein pattern with Mw 47KDa. It was identified as surface coat protein of S. glaseri which play important roles in defeating the host immune system by its antiphagocytic activity.

BIOEFFICACY OF TWO ENTOMOPATHGENIC NEMATODES AGAINST SPODOPTERALITTORALIS BOISDUVAL (LEPIDOPTERA) AND TEMNORHYNCHUS BAAL REICHE(COLEOPTERA) LARVAE

ABSTRACT Efficacy of the two entomopathogenic nematode species, Heterorhabditis bacteriophora Poinar (HP88 strain) and Steirnema glaseri Steiner (NJ strain), was tested on the fifth and third instar larvaeof Spodoptera littoralis (Boisd.) and Temnorhynchus baal (Reiche) under laboratory conditions. Experiments were conducted on filter paper and sandy soil substrates using nematode at 50, 100, 200and 400 infective juveniles/5ml of water. Heterorhabditis bacteriophora was most effective on thefifth instar larvae of S. littoralis whereas S. glaseri was effective against third instar larvae of T. ball third. Insect mortality was high (60-90%) and low (&lt;45%) at higher and lower nematodeconcentrations respectively. Heterorhabditis bacteriophora treated larvae of S. littoralis succumbedto the infection at the higher rates (80-100%) as compared to those treated with S. glaseri. The rate of mortality of S. littoralis was lowest when treated with S. glaseri (2-20%). The differences in the rateof nematode infection and insect mortality under various experimental conditions are attributed tothe difference in the behavior, virulence, rate of penetration and host searching abilities of nematodes and the abilities of insect pest larvae to resist nematode penetration. Present study suggests that entomopathogenic nematodes are important and effective biological control agents of most soil dwelling insect pests.

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.

Comparison of efficacy of nine new heterorhabditid isolates (Rhabditida: Heterorhabditidae) in Tenebrio molitor (Coleoptera: Tenebrionidae)

The virulence of new nine heterorhabditid isolates from South Carolina (Heterorhabditis megidis LEX, Heterorhabditis zealandica EDS and CHR, and Heterorhabditis bacteriophora WPS, SMP, PD, CFG, MF and CFM strains) on the yellow mealworm 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 Tenebrio molitor larvae to the heterorhabditids at concentrations of 5, 10, 25, and 100 infective juveniles (IJs) per larva. Mortalities were counted for 4 days. At the final count, mortalities were 27.1-79.9, 48.7-85.2, 82-100, and 93.8-100% for all nematode strains at the concentrations of 5, 10, 25, and 100 IJs per larva, respectively. H. megidis LEX strain differed than others by having 100% mortality in both 25 and 100 nematode concentrations. It had also the highest mortality rate with 80% at 5 nematodes per larva and H. bacteriophora HP88, WPS and SMP strains followed it with 70.1, 70.1 and 64.6% mortality, respectively. LC50 value for the nematodes was relatively low ranging from 1.74 IJs per larva for H. bacteriophora WPS strain to 11.12 IJs per larva for H. bacteriophora Hb strain. The LT50 value ranged from 1.30 to 5.31 days. Our results suggest that H. bacteriophora WPS, SMP, and CFM, and H. megidis LEX strains may be considered first to be studied further as potential biocontrol agents of insects. Key words: Biological control, entomopathogenic nematodes, Heterorhabditis, Tenebrio molitor, yellow mealworm.

Relationship between the successful infection by entomopathogenic nematodes and the host immune response

Reproduction of entomopathogenic nematodes requires that they escape recognition by a host’s immune system or that they have mechanisms to escape encapsulation and melanization. We investigated the immune responses of larvae for the greater wax moth ( Galleria mellonella), tobacco hornworm ( Manduca sexta), Japanese beetle ( Popillia japonica), northern masked chafer ( Cyclocephala borealis), oriental beetle ( Exomala orientalis) and adult house crickets ( Acheta domesticus), challenged with infective juveniles from different species and strains of entomopathogenic nematodes. The in vivo immune responses of hosts were correlated with nematode specificity and survival found by infection assays. In P. japonica, 45% of injected infective juveniles from Steinernema glaseri NC strain survived; whereas the hemocytes from the beetle strongly encapsulated and melanized the Heterorhabditis bacteriophora HP88 strain, S. glaseri FL strain, Steinernema scarabaei and Steinernema feltiae. Overall, H. bacteriophora was intensively melanized in resistant insect species ( E. orientalis, P. japonica and C. borealis) and had the least ability to escape the host immune response. Steinernema glaseri NC strain suppressed the immune responses in susceptible hosts ( M. sexta, E. orientalis and P. japonica), whereas S. glaseri FL strain was less successful. Using an in vitro assay, we found that hemocytes from G. mellonella, P. japonica, M. sexta and A. domestica recognized both nematode species quickly. However, many S. glaseri in M. sexta and H. bacteriophora in G. mellonella escaped from hemocyte encapsulation by 24 h. These data indicate that, while host recognition underlies some of the differences between resistant and susceptible host species, escape from encapsulation following recognition can also allow successful infection. Co-injected surface-coat proteins from S. glaseri did not protect H. bacteriophora in M. sexta but did protect H. bacteriophora in E. orientalis larva; therefore, surface coat proteins do not universally convey host susceptibility. Comparisons of surface coat proteins by native and SDS–PAGE demonstrated different protein compositions between H. bacteriophora and S. glaseri and between the two strains of S. glaseri.

Parasitism of Subterranean Termites (Isoptera: Rhinotermitidae: Termitidae) by Entomopathogenic Nematodes (Rhabditida: Steinernematidae; Heterorhabditidae)

In laboratory bioassays, Steinernema riobrave Cabanillas, Poinar and Raulston (355 strain), Steinernema carpocapsae (Weiser) (Mexican 33 strain), Steinernemafeltiae (Filipjev) (UK76 strain), and Heterorhabditis bacteriophora Poinar (HP88 strain) were all capable of infecting and killing three termite species, Heterotermes aureus (Snyder), Gnathamitermes perplexus (Banks), and Reticulitermes flavipes (Kollar) in laboratory sand assays. S. riobrave and S. feltiae caused low levels of Reticulitermes virginicus (Banks) mortality under the same conditions. At 22 degrees C, significant mortality (> or = 80%) of worker H. aureus and G. perplexus was caused by S. riobrave, in sand assays, indicating the need for further study. Because of the short assay time (3 d maximum), reproduction of the nematodes in the target host species was not recorded. All nematode species were observed to develop to fourth-stage juveniles, preadult stages, or adults in all termite species with the exception of R. virginicus. Only S. riobrave developed in R. virginicus. Nematode concentration and incubation time had significant effects on the mortality of worker H. aureus. S. riobrave consistently generated the highest infection levels and mortality of H. aureus in sand assays.

Laboratory Evaluation of Virulence of Heterorhabditid Nematodes toPlodia interpunctellaHübner (Lepidoptera: Pyralidae)

The Indianmeal moth, Plodia interpunctella (Hubner), is a cosmopolitan pest of stored products, infesting most commodities in warehouses and grain bins. We studied the susceptibility of Indianmeal moth adults and larvae to seven entomopathogenic nematode species and strains. The nematodes studied were Heterorhabditis bacteriophora Poinar (HP88, Lewiston, and Oswego strains); H. indica Poinar, Karunakar, and David (Homl strain); H. marelatus Liu and Berry (Point Reyes strain); H. megidis Poinar, Jackson, and Klein (UK211 strain); and H. zealandica Poinar (NZH3 strain). Overall, the nematodes that had the highest virulence to larvae and adults of Indianmeal moth were H. indica, H. megidis, and H. marelatus. Adult Indianmeal moths seemed to be more susceptible to the nematodes than the larvae, and egg laying was significantly reduced by at least 44% in Indianmeal moths adults that survived exposure to the nematode strains. We conclude that H. indica, H. megidis, and H. marelatus should be studied further as potential biocontrol agents of Indianmeal moth in stored grains and processed commodities.

Enhanced consistency in biological control of white grubs (Coleoptera: Scarabaeidae) with new strains of entomopathogenic nematodes

Abstract Achieving predictability (i.e., consistency of control) is a key challenge in the use of entomopathogenic nematodes for pest control. As nematode species/strain plays a key role in the success of white grub control, two strains, Heterorhabditis zealandica X1 (Hz-X1) and Heterorhabditis bacteriophora GPS11 (Hb-GPS11), identified through laboratory assays to be the most virulent, were tested in a series of field trials against the second and third instar white grubs Popillia japonica and Cyclocephala borealis at different locations over a 2-year period. The HP88 strain of H. bacteriophora (Hb-HP88), the NJ and MB strains of Steinernema glaseri (Sg-NJ and Sg-MB) and a UK strain of Steinernema kraussei (Sk-UK) were also included for comparison in some tests. Overall, Hz-X1 and Hb-GPS11 strains were the most effective nematodes resulting in 73–98 and 34–97% control of P. japonica and 72–96 and 47–83% control of C. borealis, respectively. The Hz-X1 and Hb-GPS11 strains did not differ significantly between each other against either grub species in any of the tests. The Hb-HP88 provided 52 and 36% control of P. japonica and C. borealis, respectively. The Sg-MB provided 6–58% control of P. japonica, no control of C. borealis, and 54–74% control of mixed populations of the two species. The Sg-NJ provided 20% control of P. japonica. Doubling the nematode application rate from 2.5 × 109 to 5 × 109 infective juveniles/ha did not significantly increase control of a mixed population of P. japonica and C. borealis. Halofenozide (Mach 2 2SC) and imidacloprid (Merit 75WP) applied as preventative treatments in July provided 97 and 98% control, respectively, of P. japonica. Imidacloprid applied as a curative treatment in September provided 47% control of C. borealis but 0% control of P. japonica. Trichlorfon (Dylox 6.2G) applied as a curative treatment in September provided 29–92% control of P. japonica, 49% control of C. borealis, and 0–77% control of mixed populations of the two grub species. Grub control provided by the Hz-X1 strain was always equal to or better than trichlorfon and that by the Hb-GPS11 strain was equal to trichlorfon except for one occasion. The amount of post-application irrigation plus rainfall had a strong effect on nematode efficacy. A total of 10 cm of post-application irrigation plus rainfall was found to be optimum at which the Hb-GPS11 and Hz-X1 strains produced 83–97 and 96–98% control of the two white grub species, respectively. Combined analyses of the results from all 8 trials containing 46 treatments indicate that the consistency in the control of P. japonica and C. borealis by the new Hz-X1 and the Hb-GPS11 strains is equal to or better than the curative application of chemical insecticide standard, trichlorfon.

Non‐target effects of entomopathogenic nematodes on the soil nematode community

1 There is growing awareness that biological control carries risks as well as benefits, but there are few data on below-ground effects of inundative insect pathogens. We addressed this issue using entomopathogenic nematodes and the soil nematode community in a turfgrass ecosystem as a model. 2 Application of Heterorhabditis bacteriophora strain GPS11, Heterorhabditis bacteriophora strain HP88 and Heterorhabditis indica strain LN2 significantly reduced the abundance, species richness, diversity and maturity of the nematode community by reducing the number of genera and abundance of plant-parasitic, but not free-living, nematodes. 3 Our results are the first to indicate selective suppression of plant-parasitic nematodes by entomopathogenic nematodes, H . bacteriophora and H. indica , with no adverse effect on free-living nematodes. 4 In contrast to the entomopathogenic nematode treatments, trichlorfon (a commonly used insecticide in turfgrass) reduced the number of genera, abundance and diversity of the nematode community by adversely affecting both plant-parasitic and free-living nematodes. 5 The reduction in abundance and diversity of plant-parasitic nematodes without any adverse effect on free-living nematodes that play a role in nutrient cycling, can be considered as a beneficial non-target effect of entomopathogenic nematodes. The mechanisms causing such an effect need to be elucidated in future studies.

Laboratory Evaluations of Four Entomopathogenic Nematodes for Control of Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract The infectivity of four species of entomopathogenic nematodes, Steinernema carpocapsae (Weiser) [Breton strain], Steinernema riobrave Cabanillas, Poinar & Raulston [Weslaco strain], Heterorhabditis bacteriophora Poinar [HP88 strain], and Heterorhabditis indica Poinar, Karunakar & David [Coimbatore strain] was examined in the laboratory against two subterranean termites: Reticulitermes flavipes (Kollar) and Coptotermes formosanus Shiraki. In petri dish tests, they were all effective against C. formosanus at ≥400 nematodes per termite. Steinernema riobrave had no detectable effect against R. flavipes even at a rate of 2,000 nematodes per termite. The virulence of the nematodes for R. flavipes was H. indica > H. bacteriophora > S. carpocapsae > S. riobrave. The virulence of the nematodes for C. formosanus was H. indica and H. bacteriophora > S. carpocapsae and S. riobrave at α = 0.10 level. The LD50 of H. indica against R. flavipes in petri dishes and in containers with vermiculite/sand medium were ...

Virulence of entomopathogenic nematodes to pecan weevil larvae, Curculio caryae (Coleoptera: Curculionidae), in the laboratory.

The pecan weevil, Curculio caryae (Horn), is a key pest of pecans in the Southeast. Entomopathogenic nematodes have been shown to be pathogenic toward the larval stage of this pest. Before this research, only three species of nematodes had been tested against pecan weevil larvae. In this study, the virulence of the following nine species and 15 strains of nematodes toward fourth-instar pecan weevil was tested: Heterorhabditis bacteriophora Poinar (Baine, HP88, Oswego, NJ1, and Tf strains), H. indica Poinar, Karunakar & David (original and Homl strains), H. marelatus Liu & Berry (IN and Point Reyes strains), H. megidis Poinar, Jackson & Klein (UK211 strain), H. zealandica Poinar (NZH3 strain), Steinernema riobrave Cabanillas, Poinar & Raulston (355 strain), S. carpocapsae (Weiser) (All strain), S. feltiae (Filipjev) (SN strain), and S. glaseri (Steiner) (NJ43 strain). No significant difference in virulence was detected among nematode species or strains. Nematode-induced mortality was not significantly greater than control mortality (in any of the experiments conducted) for the following nematodes: H. bacteriophora (Baine), H. zealandica (NZH3), S. carpocapsae (All), S. feltiae (SN), S. glaseri (NJ43), and S. riobrave (355). All other nematodes caused greater mortality than the control in at least one experiment. Heterorhabditis megidis (UK211) but not H. indica (original) displayed a positive linear relationship between nematode concentration and larval mortality. Results suggested that, as pecan weevil larvae age, they may have become more resistant to infection with entomopathogenic nematodes.

Environmental factors affecting sexual differentiation in the entomopathogenic nematode Heterorhabditis bacteriophora

The present study was aimed at determining the influence of various environmental factors on sex differentiation (SD) in the entomopathogenic nematode Heterorhabditis bacteriophora HP88 strain, under in vivo and in vitro culture conditions. Injection of individual nematodes into last instars of Galleria mellonella resulted in development of a similar number of females and hermaphrodites (35–40%) and 20–25% males. Increasing the number of nematodes injected into the insect did not change these proportions. In smaller insects (0.7–1.5 cm long), an increase in the proportion of hermaphrodites was recorded as compared with larger size cadavers (2.4–2.7 cm long). When individual hermaphrodites were placed on NGM, the proportion of hermaphrodites, females and male progeny was 63%, 31%, and 6%, respectively. Rearing on richer medium (“Dog-food” agar) resulted in reduction in the proportion of hermaphrodites. Nematodes introduced to the symbiotic bacterium obtained from other nematode strains (IS-5 and IS-33) developed similarly to the culture reared on the HP88 bacteria. Rearing the nematodes at a temperature range between 21°C to 30°C also did not have a significant effect on the sexual differentiation among nematodes cultured on NGM. The proportion of hermaphrodites increased as the starvation period of hatching nematode juveniles lengthened (>6 hr). The data obtained in the present study strongly suggest that the main factor affecting sex differentiation in H. bacteriophora is the nutrition source. The practical and biological implications of the results are discussed. J. Exp. Zool. 287:158–166, 2000. © 2000 Wiley-Liss, Inc.

Environmental factors affecting sexual differentiation in the entomopathogenic nematodeHeterorhabditis bacteriophora

The present study was aimed at determining the influence of various environmental factors on sex differentiation (SD) in the entomopathogenic nematode Heterorhabditis bacteriophora HP88 strain, under in vivo and in vitro culture conditions. Injection of individual nematodes into last instars of Galleria mellonella resulted in development of a similar number of females and hermaphrodites (35-40%) and 20-25% males. Increasing the number of nematodes injected into the insect did not change these proportions. In smaller insects (0.7-1.5 cm long), an increase in the proportion of hermaphrodites was recorded as compared with larger size cadavers (2.4-2.7 cm long). When individual hermaphrodites were placed on NGM, the proportion of hermaphrodites, females and male progeny was 63%, 31%, and 6%, respectively. Rearing on richer medium ("Dog-food" agar) resulted in reduction in the proportion of hermaphrodites. Nematodes introduced to the symbiotic bacterium obtained from other nematode strains (IS-5 and IS-33) developed similarly to the culture reared on the HP88 bacteria. Rearing the nematodes at a temperature range between 21 degrees C to 30 degrees C also did not have a significant effect on the sexual differentiation among nematodes cultured on NGM. The proportion of hermaphrodites increased as the starvation period of hatching nematode juveniles lengthened (>6 hr). The data obtained in the present study strongly suggest that the main factor affecting sex differentiation in H. bacteriophora is the nutrition source. The practical and biological implications of the results are discussed.