Differences in activity between infective juveniles (IJ) of the entomopathogenic nematode Steinernema carpocapsae that emerged directly from cadavers onto either a sand or agar substrate compared with those emerging from a cadaver into water and then being placed on the same substrate are known to occur. Differences between S. carpocapsae IJ that emerged directly from a cadaver vs. those that emerged from a cadaver and held in water were further elucidated. Dispersed and non-dispersed IJ from a cadaver were compared with those held in water between two time periods designated as early- (first two days) or late-emerging IJ (seventh day). A significantly greater proportion of early-emerging IJ from the cadaver treatment dispersed, compared with late-emerging IJ from a cadaver or either group of emerging IJ held in aqueous suspension. Moreover, IJ from cadavers were more infectious than those from the aqueous suspensions, and IJ that dispersed were less infectious than those that did not disperse. IJ that emerged early were mostly males, whereas those that emerged late were mostly females. For the non-dispersed IJ, most that emerged early were males, and those that emerged later were females, but among dispersing IJ, there was no difference in sex ratio between early- and late-emerging nematodes.
Ambush forager; foraging behavior; insect-parasitic nematode; Steinernema carpocapsae; Steinernematidae
Two Hawaiian isolates of Steinernema feltiae MG-14 and Heterohabditis indica MG-13, a French isolate of S. feltiae SN, and a Texan isolate of S. riobrave TX were tested for their efficacy against the root-knot nematode, Meloidogyne javanica, in the laboratory and greenhouse. Experiments were conducted to investigate the effects of treatment application time and dose on M. javanica penetration in soybean, and egg production and plant development in tomato. Two experiments conducted to assess the effects of entomopathogenic nematode application time on M. javanica penetration demonstrated that a single application of 10⁴ S. feltiae MG-14 or SN infective juveniles per 100 cm³ of sterile soil, together with 500 (MG-14) or 1,500 (SN) second-stage juveniles of M. javanica, reduced root penetration 3 days after M. javanica inoculation compared to that of a water treatment. Entomopathogenic nematode infective juveniles applied to assess the effects on M. javanica egg production did not demonstrate a significant reduction compared to that of the water control treatment. There was no dose response effect by Steinernema spp. On M. javanica root penetration or egg production. Steinernema spp. did not affect the growth or development of M. javanica-infected plants, but H. indica MG-13-treated plants had lower biomass than untreated plants infected with M. javanica. Infective juveniles of S. riobrave TX, S. feltiae SN, and MG-14 but not those of H. indica MG-13 were found inside root cortical tissues of M. javanica-infected plants. Entomopathogenic nematode antagonism to M. javanica on soybean or tomato was insufficient in the present study to provide a consistent level of nematode suppression at the concentrations of infective juveniles applied.
behavior; heterorhabditis; Meloidogyne javanica; root penetration; Steinernema; suppression
Exposure to NaC1, KCI, and CaCl₂ affected the entomopathogenic nematodes Heterorhabditis bacteriophora and Steinernema glaseri differently. Survival, virulence, and penetration efficiency of S. glaseri were not affected by these salts. At high concentrations, however, all three salts inhibited its ability to move through a soil column and locate and infect a susceptible host. Calcium chloride and KCl had no effect on H. bacteriophora survival, penetration efficiency, or movement through a soil column, but moderate concentrations of these salts enhanced H. bacteriophora virulence. NaCl, however, adversely affected each of these parameters at high salinities (>16 dS/m). Salt effects on S. glaseri are attributed solely to interference with nematode host-finding ability, whereas the NaCl effects on H. bacteriophora are attributed to its toxicity and possibly to interference with host-finding behavior.
Entomopathogenic nematode; Heterorhabditis bacteriophora; infectivity; nematode; salinity; survival; Steinernema glaseri
The impact of the nematode-parasitic fungus Hirsutella rhossiliensis on the effectiveness of Steinernema carpocapsae, S. glaseri, and Heterorhabditis bacteriophora against Galleria mellonella larvae was assessed in the laboratory. The presence of Hirsutella conidia on the third-stage (J3) cuticle of S. carpocapsae and H. bacteriophora interfered with infection of insect larvae. Conidia on the J3 cuticle of S. glaseri and on the ensheathing second-stage cuticle of H. bacteriophora did not reduce the nematodes' ability to infect larvae. The LD₅₀ values for S. carpocapsae, S. glaseri, and H. bacteriophora in sand containing H. rhossiliensis were not different from those in sterilized sand when Galleria larvae were added at the same time as the nematodes. However, when Galleria larvae were added 3 days after the nematodes, the LD₅₀ of S. glaseri was higher in Hirsutella-infested sand than in sterilized sand, whereas the LD₅₀ of H. bacteriophora was the same in infested and sterilized sand. Although the LD₅₀ of S. carpocapsae was much higher in Hirsutella-infested sand than in sterilized sand, the data were too variable to detect a significant difference. These data suggest that H. bacteriophora may be more effective than Steinernema species at reducing insect pests in habitats with abundant nematode-parasitic fungi.
biological control; entomopathogenic nematode; fungus; Heterorhabditis; Hirsutella rhossiliensis; nematode; nematophagous fungus; Steinernema
Adults of the brown planthopper (BPH) and the whitebacked planthopper (WBPH) that migrated into Korea from China were not parasitized by the mermithid, Agamermis unka. BPH and WBPH collected from Korean rice fields were parasitized. Parasitism of BPH in the lst-3rd, 4th, and 5th instars, and adults was 31.5%, 61.5%, 66.4%, and 45.5%, respectively, whereas parasitism of the same stages of WBPH was 50%, 50%, 100% and 90.7%, respectively. Parasitism of BPH by A. unka significantly reduced the number of eggs. Only 4.2% of the parasitized females contained eggs, whereas 85.6% of unparasitized females had eggs. Tilling of rice fields significantly increased mermithid parasitism of BPH. Mermithids parasitized 39.3% of caged adults in the untilled field and 77.8% in the tilled field.
Agamermis unka; biological control; brown planthopper; entomogenous nematode; mermithid; Nilaparvata lugens; rice pest; Sogatella furcifera; whitebacked planthopper
Survival of infective juveniles of Steinernema carpocapsae and Steinernema glaseri gradually declined during 16 weeks of observation as the tested soil pH decreased from pH 8 to pH 4. Survival of both species of Steinernema dropped sharply after 1 week at pH 10. Survival or S. carpocapsae and S. glaseri was similar at pH 4, 6, and 8 during the first 4 weeks, but S. carpocapsae survival was significantly greater than S. glaseri at pH 10 through 16 weeks. Steinernema carpocapsae and S. glaseri that had been stored at pH 4, 6, and 8 for 16 weeks, and at pH 10 for 1 or more weeks were not infective to Galleria mellonella larvae. Steinernema carpocapsae survival was significantly greater than that of S. glaseri at oxygen:nitrogen ratios of 1:99, 5:95, and 10:90 during the first 2 weeks, and survival of both nematode species declined sharply to less than 20% after 4 weeks. Survival of both nematode species significantly decreased after 8 weeks as the tested oxygen concentrations decreased from 20 to 1%, and no nematode survival was recorded after 16 weeks. Steinernema carpocapsae pathogenicity was significantly greater than that of S. glaseri during the first 2 weeks. No nematode pathogenicity was recorded at oxygen concentrations of 1, 5, and 10% after 2 weeks and at 20% after 16 weeks.
entomopathogenic nematode; pathogenicity; Steinernema carpocapsae; Steinernema glaseri; survival
entomogenous nematode; entomopathogenic nematode; fenamiphos; IPM; nematicide; Steinernema feltiae; steinernematid
The mermithid Agamermis unka, a parasite of the brown planthopper (BPH), was found in many rice paddies in Gyeongnam Province, Korea. Nematode parasitism of adult BPH varied from year to year, reaching as high as 50% in paddies not treated with an insecticide. Parasitism was lower in insecticide-treated paddies. Generally, mermithid parasitism was higher in BPH adults collected from the lower part (19%) compared with adults collected from the upper part (8%) of the rice plant and in brachypterous (57%) compared with macropterous forms (8%). No difference in parasitism between first (54%) and second (57%) generation was observed.
Agamermis unka; biological control; brown planthopper; entomogenous nematode; integrated control; mermithid; Nilaparvata lugens; rice pest
Nematodes found in Ips paraconfusus from ponderosa pine in California were an undescribed species of Parasitaphelenchus, Contortylenchus elongatus, C. reversus, and C. brevicomi. C. elongatus, the most commonly found contortylenchid, was present in 98.2% of the contortylenchid-parasitized beetles. Only one nematode parasite of the gut, a Parasitorhabditis sp., was isolated. Although significant differences in parasitism were observed, they were by collection sites, rather than by elevation or bole sources (slash or standing). Significant changes in parasitism between fall and spring collections were observed but not at every site. Nematode parasitism in the F₁ generation of I. paraconfusus by Parasitaphelenchus, Contortylenchus, or Parasitorhabditis increased or decreased from the parent generation depending upon the experiment.
Nematode parasites from I. pini included an undescribed Parasitaphelenchus sp., two undescribed Contortylenchus spp., C. reversus and Parasitylenchus (= Neoparasitylenchus) ovarius from the hemocel, and Parasitorhabditis ipini from the gut. Parasitaphelenchus sp. was found in 99% and 45.3% of the beetles from Idaho and California, respectively. Of the 1,000 I. pini from Idaho and California, 157 were parasitized by the contortylenchid species or P. ovarius.
bark beetle; biological control; Contortylenchus; entomogenous nematode; Ips; parasitism; Parasitaphelenchus; Parasitorhabditis; Parasitylenchus; Pinus
The entomogenous nematode Steinernema feltiae was encapsulated in an alginate matrix containing a tomato seed. When these capsules were placed on 0.8% agar for 7 days, the seed germinated and ca. 20% of the nematodes escaped from the capsules, whereas only 0.1% escaped from capsules without seeds. When capsules containing nematodes and a seed were planted into sterilized or nonsterilized soil, nematodes escaped to infect Galleria mellonella larvae. When seed in capsules containing ca. 274 nematodes per capsule were planted in nonsterilized soil, Galleria mortality was 90% 1 week later. Galleria mortality declined to 27%, 23%, and 0% in weeks 2, 4, and 8 postplant, respectively. In sterilized soil, Galleria mortality was 96% and did not differ significantly from the nonsterilized soil in week 1, but was significantly higher in sterilized soil over nonsterilized soil for week 2 (81%) and week 4 (51%). When capsules containing nematodes only were used, Galleria mortality was 71% in sterilized soil 1 week after planting and 58%, 33%, and 12% in weeks 2, 4, and 8 postplant, respectively. In nonsterilized soil, Galleria mortality was 8%, 30%, 21%, and 28% after 1, 2, 4, and 8 weeks, respectively, using only encapsulated nematodes. When the number of nematodes per capsule was increased to ca. 817, Galleria mortality was 92 % or higher in sterilized soil from week 1 to week 4.
biological control; calcium alginate; Galleria mellonella; Neoaplectana; sodium alginate; Steinernema feltiae; tomato
The entomogenous nematode Neoaplectana carpocapsae and its associated bacterium, Xenorhabdus nematophilus, could not infect the pupal stage of the tachinid Compsilura concinnata through the puparium. N. carpocapsae had an adverse effect on 1-, 2- and 3-day-old C. concinnata larvae within the armyworm host in petri dish tests. All 1-day-old larvae treated with nematodes died in their hosts, whereas 61% and 69% of 2- and 3-day-old larvae treated with nematodes, respectively, died. However, the survivors developed to adults. Nine to thirty-seven percent of adult tachinids which emerged from nematode-treated soil (50 nematodes/cm²) were infected with N. carpocapsae. The nematode adversely affects C. concinnata directly by the frank infection of the tachinid and indirectly by causing the premature death of the host which results in tachinid death.
interaction between parasite and nematode; biological control; insect-nematode interaction
entomogenous nematode; morphology; biocontrol
The effects of organophosphates (mevinphos, phenamiphos, trichlorfon), carbamates (carbofuran, methomyl, oxamyl), a formamidine (chlordimeform), a synthetic pyrethroid (fenvalerate), a chlorinated hydrocarbon (methoxychlor). and an insect growth regulator (diflubenzuron) on in vitro development and reproduction of Neoaplectana carflocapsae were tested by incorporating each chemical into a nematode rearing medium. Organophosphates and carbamates adversely affected development and reproduction at concentrations ≥ 0.1 mg/ml. Phenamiphos was the most toxic, with no nematode reproduction at 0.01 mg/ml. Inoculated infective juveniles developed to adults with some of the organophosphates and carbamates, but limited or no reproduction occurred. Chlordimeform inhibited development at 1.0 mg/ml, while diflubenzuron, fenvalerate, and methoxychlor did not significantly (P > 0.05) reduced reproduction at 1.0 mg/ml. The organophosphate and carbamate nematicides in use for control of plant-parasitic nematodes may be toxic to N. carpocapsae in the soil.
organophosphates; carbamates; integrated pest management; biological control
The susceptibility of certain species of lepidopterous pupae occurring in different ecological situations to the entomogenous nematode, Neoaplectana carpocapsae, was tested. Soil- or litter-pupating lepidopterous insects were not highly susceptible to N. carpocapsae. The most susceptible insect pupating in the soil was Spodoptera exigua with 63% pupal mortality, while Harrisinia brillians, which pupates in litter, had 55% mortality. Other soil- and litter-pupating insects had mortalities of less than 25%. Some insect species that pupate above ground were highly susceptible (> 84% mortality) to N. carpocapsae infection.
biological control; nematode infection; pupal mortality
Laboratory tests determined the lateral and vertical dispersal patterns of Neoaplectana carpocapsae in sand. In the vertical tests, placement of infective juveniles 15 cm below the sand's surface resulted in the majority (77%) being recovered above the point of placement after 48 h. Placement of the nematodes on the sand's surface resulted in the majority (90.4%) remaining within 1 cm of the sand's surface. Placement of nematodes at depths of 2.5 cm and 5.0 cm below the sand's surface also resulted in little nematode dispersal. However, vertical hioassay tests showed that juvenile nematodes placed on the sand's surface dispersed 12 cm down to infect 67% of the Galleria mellonella pupae placed at the depth. Conversely, when nematodes were placed 11 cm below the insect pupae no infection was observed, but 53% infection occurred when nematodes were 7 cm below the site of the insect pupae. In lateral dispersal, 87% of the nematodes rentained within 2 cm of the placement site, although 0.5% were recovered at 12-14 cm away from the point of placement. Lateral bioassay tests indicated that the nematodes were capable of infecting 90, 35, and 5% of the G. mellonella pupae at 7 cm, 10 cm, and 14 cm from the point of placement, respectively.
DD-136 nematode; biological control; entomophilic nematode; dispersal; nematotte movement
Helerolylenchus aulumnalis was found in six northern California counties surveyed, and the incitlence of nematode infection of face flies ranged from 4.7 to 43.8%. Intensive studies at a cattle ranch in Yuba County showed that population densities of the host and nematode infections were highest in flies from cow pats receiving full sun. Average host population density was 105.7 puparia per pat, and nematode infection averaged 38.6%. Pats in partial sun averaged 13.5 puparia and 13,1% nematode infection. No face fly was recovered from shaded pats. When data from pats first exposed during day or night were compared, no significant differences in host population density or nematode infection rates were apparent. Uninfected and superinfected flies were more frequent than predicted by a Poisson distribution.
Infected and uninfected female flies of all ages captured on white sticky traps appeared to feed with similar frequency upon a creatny substance which was probably acquired from cattle, However, older infected females fed less on blood and more upon dung than older uninfected females. Percent nematode infection and host population densities were highest in spring and early summer, declined to a midsummer low, and then increased slightly. Both dung-reared flies and captured females showed similar trends in abundance anti infection rates. Regression analysis indicated that H. autumnalis may not be regulating face fly population density.
Biological control; host-parasite relationships; insect-nematode relationships; population dynamics
Neoaplectaua carpocapsae developed and reproduced in armyworm hosts infected with a granulosis virus (GV). Macerated tissues of dauer juveniles from GV-infecled hosts had sufficient GV to infect 1st and 2nd instar armyworms. Electron-microscope examination of dauer juveniles and adult female nematodes confirmed the presence of GV in the lumen of the intestine. No GV was observed in other tissues of the nematode.
DD-136 nematode; nematode-insect virus interaction; insect virus; Baculovirus
The infectivity of Neoaplectana carpocapsae and Heterorhabditis heliothidis to Apanteles militaris, a gregarious parasite of the armyworm, was deterntined at 100. 1,000, 5,000, and 10,000 nematodes per petri dish. For both nematode species, the percentage of infected A. militaris within a cocoon cluster decreased as inoculum levels decreased. At the highest inoculum level, N. carpocapsae infected an average of 32% of the parasite pupae within a cocoon cluster, whereas H. heliothidis infected an average of 22%. Covariance analysis indicated, however, that N. carpocapsae had significantly greater infectivity than did H. heliothidis. Some of the dauer juveniles of N. carpocapsae on the body of the armyworm contacted the emerging parasites and eventually became enveloped within the silken cocoons. Dauer juveniles produced by N. carpocapsae in parasite pupae could not penetrate and escape from silken cocoons even when the cocoons were placed in a moist environment.
nematode-insect parasite interaction
The development of the DD-136 strain of Neoaplectana carpocapsae was studied on three food sources at 10, 15, 20, 25, 30, 33, 35, and 37 C. No growth occurred at 10 or above 33 C. At 15, 20. and 25 C, growth and reproduction occurred. The most favorable growth occurred at 25 C. At 30 C, N. carpocapsae developed to adults but did not reproduce. Key Words: temperature-growth effects, DD-136 strain.