Restricted Access

Chau N. Nguyen, Anh T. Do, Phap Q. Trinh and Phuc K. Hoang

Summary

The virulence and efficacy of two species of entomopathogenic nematodes, Steinernema sp. (strain PQ16) and Heterorhabditis indica (strain KT3987), against nymphs of the coffee cicada, Dundubia nagarasingna, was evaluated under laboratory and glasshouse conditions. The highest mortality rates of coffee cicada nymphs caused by these two nematode strains were 93.5 and 100%, respectively, at an inoculation dose of 600 infective juveniles (IJ) nymph−1. The virulence (LC50) was established as 137.5 IJ and 149.1 IJ for strains S-PQ16 and H-KT3987, respectively. The highest IJ yields of these nematode strains were 66 × 103 IJ (for S-PQ16) and 134.4 × 103 IJ (for H-KT3987) at a dose of 500 IJ nymph−1. The efficacies of the two nematode strains to coffee cicadas at treated dose of 60 × 103 IJ pot−1 were 84.4 and 88.9% after 30 days, higher than the efficacies at treated dose of 40 × 103 IJ pot−1. The number of IJ in 250 ml of soil at 10, 20 and 30 days after treatment, increased from 0.38 × 103 to 4.80 × 103 IJ in soil treated with a dose of 40 × 103 IJ and from 0.66 × 103 to 5.02 × 103 IJ in soil treated with a dose of 60 × 103 IJ (for S-PQ16). Similarly, for H-KT3987 the number of IJ increased from 0.43 × 103 to 8.99 × 103 IJ and from 0.62 × 103 to 9.64 × 103 IJ, at the respective doses. Based on results of a pot trial from glasshouse modelling, an IJ application dosage for biological control of coffee cicada nymphs in coffee plantations was proposed.

Restricted Access

Naser Eivazian Kary, Samira Chahardoli, Davoud Mohammadi and Aoife B. Dillon

Summary

The virulence of entomopathogenic nematodes (EPN) Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora was evaluated against the diamondback moth, Plutella xylostella. The results revealed that diamondback moth mortality was affected by its developmental stage. For both Steinernema species, diamondback moth larval mortality peaked at 18 infective juveniles (IJ) larva−1; similar results were recorded for H. bacteriophora, with mortality peaking at 20 IJ larva−1. Mortality of pre-pupa exposed to Steinernema species increased up to 35 IJ pre-pupa−1; in S. feltiae a decreasing trend was recorded at higher concentrations of IJ. A negative correlation was recorded between LC50 and ln ET values; S. carpocapsae appeared as the most virulent EPN against larvae (6.5 IJ larva−1) and H. bacteriophora was an effective EPN against pre-pupae (6.5 IJ pre-pupa−1). EPN virulence at dose levels was evaluated by plotting LC50 against ln exposure time, and in the majority of data sets deviations from a linear model were observed and data were statistically fitted by a two-stage phase.

Restricted Access

Kaikai Qiao, Mengxin Bai, Qiu Wang, Xiangyu Hou, Jingwei Chen, Shun Xiao, Guokun Liu, Wim Bert and Xue Qing

Summary

Species of the family Tylenchidae are encountered in large numbers in soils. The genus Labrys was recently described characterised by a remarkable lip pattern that differs from all other known Tylenchidae genera. Here we describe a curious new species, Labrys fujianensis sp. n., that morphologically fits the genus Labrys but which is genetically divergent. The phylogeny was inferred based on 18S and 28S rDNA and light and scanning electron microscopy were used to extract detailed morphologies. The phylogenetic position of this species and its phenotypic convergence are discussed. The possibility of a long-branch attraction artefact was inspected both by removal of variable nucleotide sites and monophyletic testing of topologies. The results confirmed the divergent positioning of the presented species and it is demonstrated that the genetic diversity in Tylenchidae may be much higher than expected due to morphological homoplasy.

Restricted Access

Taisuke Ekino, Suguru E. Tanaka, Natsumi Kanzaki and Yuko Takeuchi-Kaneko

Summary

The virulence of Bursaphelenchus xylophilus, the pine wood nematode, varies greatly among different populations. Two inbred strains, called P3 and P9, were recently established via repeated full-sib mating. They exhibited remarkable differences in pathogenicity-related traits. Although their propagation did not differ when cultured on fungal lawns, P9 reproduced better in host seedlings and exhibited higher virulence. In the present study, we obtained fundamental information about P3 and P9 in terms of tolerance to oxidative stress and examined this tolerance and the cuticular ultrastructure. P9 survived better under hydrogen peroxide (H2O2)-stressed conditions than did P3. In addition, P9 had a thicker cuticle than P3. Although further studies are needed, these results suggest that the difference in tolerance in P3 and P9 was due not only to physiological features, such as H2O2-degrading ability, but also to physical factors (cuticle thickness).

Restricted Access

Natsumi Kanzaki, Taisuke Ekino, Tatsuya Ide, Hayato Masuya and Yousuke Degawa

Summary

Three parasitaphelenchid species, Parasitaphelenchus frontalis n. sp., P. costati n. sp. and Bursaphelenchus hirsutae n. sp., are described. Parasitaphelenchus frontalis n. sp. was isolated from the body cavity of Scolytus frontalis emerging from dead logs of Zelkova serrata collected from Kanagawa, Japan, and characterised by its four-lined lateral field in the adults and dome-shaped lip region of the parasitic juveniles. Whereas the two first-mentioned species were isolated from Alniphagus costatus, B. hirsutae n. sp. emerged from dead logs of Alnus hirsuta collected from Nagano, Japan. Parasitaphelenchus costati n. sp. and B. hirsutae n. sp. were recovered from the body cavity and the underside of the elytra of their host/carrier beetle, respectively. Parasitaphelenchus costati n. sp. is characterised by its three-lined lateral field in adults and the presence of a ventrally-directed hook on the lip region of the parasitic juvenile. Bursaphelenchus hirsutae n. sp. belongs to the eggersi group of the genus and is characterised by its three-lined lateral field, dorsally truncate condylus and pointed rostrum of males, and long, smoothly tapering and strongly ventrally recurved, female tail. Molecular characterisation is provided for all three new species and their phylogenys discussed.

Restricted Access

Reyes Peña-Santiago

Summary

Labronema ferox is redescribed on the basis of two females and four males from the USA. It is characterised by its 2.90-4.45 mm long body, lip region offset by deep constriction, 31-39 μm broad and slightly sucker-like with distinctly protruding perioral liplets, odontostyle 34-37 μm long with aperture occupying 37-42% its length, neck 673-883 μm long, pharyngeal expansion occupying 48-52% of total neck length, female genital system didelphic-amphidelphic, uterus long and complex, including an intermediate pars musculosa, vulva longitudinal (V = 51-54), caudal region short and rounded (27-39 μm, c = 93-135, c=0.6-0.8), spicules 76-89 μm long, and 20-25 nearly contiguous ventromedian supplements with an hiatus. Previous information about the species is analysed and discussed in the light of the present redescription. A new name, Labronemella zullinii sp. n., is proposed for the two females from Nepal described by Zullini in 1973. This new characterisation of L. ferox lays the foundations to study the taxonomy of the genus in more detail.

Restricted Access

Cassandra Edmunds, Rory J. Post, Craig S. Wilding and Robbie Rae

Summary

Entomopathogenic nematodes (EPN) of the families Steinernematidae and Heterorhabditidae are lethal insect parasites that have been commercialised as biological control agents. EPN have been isolated from across the world but it has been more than 20 years since the last survey of the UK, and species like Steinernema carpocapsae have never been found here and positively identified through molecular biology. We collected 518 soil samples from a diverse range of habitats across the UK and baited them with Galleria mellonella to isolate EPN. Dead G. mellonella were placed in White traps and emergent EPN underwent DNA barcoding analyses. From the 518 samples, 3.5% were positive for EPN. No Heterorhabditis species were found, but seven isolates of S. glaseri, one isolate of S. feltiae, eight isolates of S. affine and two isolates of S. carpocapsae were found. This was the first confirmed record of S. carpocapsae in the UK.

Restricted Access

Kenta Uesugi, Masaaki Katsura, Naohiro Uwatoko, Yasushi Tateishi, Gaku Murata and Kei Iwabuchi

Summary

The suppressive effect of a black oat, Avena strigosa, breeding line KH1a on Meloidogyne spp. was examined in pot tests and on Meloidogyne incognita in pot and field tests. In pot tests, roots of black oats were examined 42-46 days after inoculation of 500 second-stage juveniles. There were significantly fewer egg masses on the roots of KH1a than on 12 black oat cultivars examined. KH1a was a poor host for four isolates of M. incognita, two isolates of M. arenaria and one isolate of M. javanica, and a non-host for one isolate of M. hapla. The effect of autumn and spring cropping of KH1a on soil nematode density was examined in M. incognita-infested fields. Nematode density after autumn cropping of KH1a was significantly lower than that after susceptible black oat, resulting in significantly lower P f/P i in KH1a (0.10 and 0.13) than in susceptible black oat (0.42 and 0.74). Damage indices of the succeeding crop, sweet potato, were significantly lower in KH1a plots than in susceptible black oat plots. In spring cropping, there were significantly fewer soil nematodes in KH1a plots than in susceptible black oat plots 3 weeks after cultivation. In both autumn and spring cropping, there was no significant difference in soil nematode density between KH1a and bare fallow. These results suggested that KH1a is a good alternative to current susceptible cultivars for the management of M. incognita.

Restricted Access

Ebrahim Shokoohi, Hadi Panahi, Hendrika Fourie and Joaquín Abolafia

Summary

A population of Macrolaimus arboreus was collected from the rhizosphere of pine in Iran. This population of M. arboreus is characterised by the body length, 800-1010 μm in females, lip region with six seta-like papillae directed anteriad, stoma nearly as long as wide (9-11 × 7 μm), with cheilostom slightly longer than gymnostom and cheilorhabdia and gymnorhabdia well-developed, pharyngeal corpus 1.8-2.0 times the isthmus length, with slightly swollen metacorpus, excretory pore located at isthmus level, female reproductive system monodelphic-prodelphic reflexed with short post-vulval uterine sac, female tail conical (57-67 μm, c = 13.7-15.0, c′ = 3.5-3.8), ending in an acute tip which is weakly curved dorsad, and phasmids at 54-60% of tail length. Measurements and illustrations, including SEM, are provided.

Restricted Access

Anique Godjo, Leonard Afouda, Hugues Baimey, Marjolein Couvreur, Lionel Zadji, Gladys Houssou, Wim Bert, Anne Willems and Wilfrida Decraemer

Summary

Two nematode isolates from the genus Steinernema were collected in northern Benin. Morphological, morphometric, molecular and cross-hybridisation studies placed these nematodes into a new species, Steinernema kandii n. sp., within the bicornutum-group. Phylogenetic analyses based on both ITS and D2-D3 regions of 28S rDNA revealed that S. kandii n. sp. is different from all known Steinernema species and sister to S. abbasi (97.3-97.6% ITS nucleotide similarity) and S. bifurcatum (98.3-98.4% D2-D3 similarity). Steinernema kandii n. sp. can be separated from other members of the bicornutum-group by the greater infective juvenile (IJ) max. body diam. of 35 (27-48) μm (type isolate). It differs from S. abbasi by the greater IJ body length 707 (632-833) μm (type isolate), EP distance 55 (52-60) μm (type isolate), spicule length 67 (57-75) μm (type isolate) and the occurrence of one pair of genital papillae at the cloacal aperture.