Steve Edgington

Description of Xenorhabdus magdalenensis sp. nov., the symbiotic bacterium associated with Steinernema australe

A symbiotic bacterium, strain IMI 397775(T), was isolated from the insect-pathogenic nematode Steinernema australe. On the basis of 16S rRNA gene sequence similarity, this bacterial isolate was shown to belong to the genus Xenorhabdus, in agreement with the genus of its nematode host. The accurate phylogenetic position of this new isolate was defined using a multigene approach and showed that isolate IMI 397775(T) shares a common ancestor with Xenorhabdus doucetiae FRM16(T) and Xenorhabdus romanii PR06-A(T), the symbiotic bacteria associated with Steinernema diaprepesi and Steinernema puertoricense, respectively. The nucleotide identity (less than 97%) between isolate IMI 397775(T), X. doucetiae FRM16(T) and X. romanii PR06-A(T) calculated for the concatenated sequences of five gene fragments encompassing 4275 nt, several phenotypic traits and the difference between the upper temperatures that limit growth of these three bacteria allowed genetic and phenotypic differentiation of isolate IMI 397775(T) from the two closely related species. Strain IMI 397775(T) therefore represents a novel species, for which the name Xenorhabdus magdalenensis sp. nov. is proposed, with the type strain IMI 397775(T) ( = DSM 24915(T)).

Diversity and distribution of entomopathogenic nematodes in Chile.

A systematic programme of surveys for entomopathogenic nematodes (EPN) was done in Chile between 2006 and 2008. The survey spanned the principal ecosystems of mainland Chile as well as a number of islands, and covered a wide range of habitats including the Atacama Desert, Andean Altiplano, temperate rainforests and subpolar territory. Nearly 1400 soil samples were collected, of which 7% were positive for EPN. Of 101 EPN isolates obtained, 94 were Steinernema spp. and seven were Heterorhabditis sp. Of the 94 Steinernema isolates, 39 were identified as Steinernema feltiae , the remainder being distributed between two new species, S. unicornum (52 records) and S. australe (three records). The Heterorhabditis isolates, all designated as Heterorhabditis sp.1, are referred to herein as H . cf. safricana . Steinernema feltiae and S. unicornum were collected predominately in the south of Chile and were obtained from a range of habitats, including forests, open grassland, montane soils and coastal zones; neither species was recovered from the far north of the country ( viz ., desert soils in the Norte Grande region). Steinernema australe was found in only three soil samples, all from humid, cool, coastal localities in the south. Heterorhabditis cf. safricana was recovered from the northern regions, with most isolates found in or on the periphery of the Atacama Desert; they were not recovered from cooler, more humid regions of southern Chile. Molecular information indicated there were two subgroups of both S. unicornum and S. feltiae , with a geographical, intraspecific split of subgroups between the most southerly and the more central survey zones. All isolates were collected by ex situ baiting with waxmoth larvae and the natural hosts are unknown.

Beauveria bassiana for the control of Sunn Pest (Eurygaster integriceps) (Hemiptera: Scutelleridae) and aspects of the insect's daily activity relevant to a mycoinsecticide

Abstract A series of investigations was carried out at ICARDA during April–June 2004 and May–June 2005 to investigate the use of the entomopathogenic fungus Beauveria bassiana to control Eurygaster integriceps and to determine aspects of the insects biology that could be relevant to control with the fungus. Application in 2004 of an oil-based formulation of B. bassiana showed distribution of the spray decreasing from the top of the wheat to the bottom, although the proportion of tillers with coverage at the base was still 80%. Seventy percent of Sunn Pest had received direct hits, with the highest amount on the dorsal surface, followed by the ventral surface, then the legs and antennae. Mortality of field-treated, then laboratory-maintained insects, ranged from 47.6% for insects exposed only to the B. bassiana spray, 74.2% for unsprayed insects exposed to treated wheat and 86.4% for insects receiving direct spray and being exposed to treated wheat. Some field results demonstrated mortality. Mortality assessments following the 2005 treatments were conducted solely in the field, there was no apparent effect upon Sunn Pest numbers. The majority of studies on Sunn Pest biology were carried out on untreated insects outside the trial plots. Different assessment methods resulted in varying estimates of adults and juveniles in the field. The numbers of Sunn Pest found and the proportion of these at the top of the wheat crop, declined after early morning and increased again in the early evening, suggesting sheltering deeper in the crop or in the soil during the middle part of the day. Mobility and location of marked insects was followed in micro-plots and by mark and recapture studies, demonstrating a range of activities, from movement around the crop for a number of metres, including contact with numerous tillers to almost total immobility; Sunn Pest generally avoided movement on the soil. The potential for Sunn Pest control with a mycoinsecticide and how Sunn Pest behaviour is relevant to a mycoinsecticide application are discussed.

Steinernema australe n. sp. (Panagrolaimomorpha: Steinernematidae), a new entomopathogenic nematode from Isla Magdalena, Chile

A new species of entomopathogenic nematode, Steinernema australe n. sp., was isolated from a soil sample taken close to the beach on Isla Magdalena, an island in the Pacific Ocean, 2 km from mainland Chile. Morphologically the new species belongs to the glaseri-group and is characterised by morphometrics of the infective juvenile which has a very long body of 1316 (1162-1484) μm, excretory pore located far posterior to the anterior extremity (110 (95-125) μm), exceptionally long tail of 103 (92-114) μm, H% = 51 (42-61), E% = 107 (94-122) and a ratio = 35 (31-38). The first generation male has 72 (55-78) μm long spicules, a 45 (36-51) μm long gubernaculum and SW% = 172 (118-196). The first generation female can be recognised by well developed double epiptygmata, the lack of a prominent postanal swelling, a mucron on the tail tip and (in 60% of individuals) one to two subsidiary mucrons. Sequences of the ITS and D2D3 regions of the ribosomal DNA confirm that S. australe n. sp. is a valid species.

New entomopathogenic nematodes from semi-natural and small-holder farming habitats of Rwanda

ABSTRACT Five field surveys for indigenous entomopathogenic nematodes (EPNs) were conducted in 22 semi-natural and 17 small-holder farming habitats across 16 districts of different altitudes in the northern, eastern, southern and Kigali city provinces of Rwanda. In 2014, 216 mixed soil samples were collected and subsamples thereof baited with Galleria mellonella or Tenebrio molitor larvae. Five samples from five locations and habitats were positive for nematodes (2.8%). Nine nematode species/strains were isolated and five successfully maintained. DNA sequence comparisons and morphological examinations revealed Steinernema carpocapsae, Heterorhabditis bacteriophora, as well as two steinernematids and one heterorhabditid with no species designation. The isolates (strains) were named Steinernema sp. RW14-M-C2a-3, Steinernema sp. RW14-M-C2b-1, Steinernema carpocapsae RW14-G-R3a-2, H. bacteriophora RW14-N-C4a and Heterorhabditis sp. RW14-K-Ca. These are the first records of naturally occurring EPNs in Rwanda. It is also the first record of S. carpocapsae from Africa. Finding H. bacteriophora from tropical rather than temperate Africa was surprising. The found nematodes will serve as the basis for efficacy screening, and for mass production in a biocontrol agent factory at Rubona Research Centre of the Rwanda Agriculture Board with the ultimate aim of delivering effective, safe and environmentally benign pest control for soil-inhabiting pests.

Biology and host range testing of Triarthria setipennis and Ocytata pallipes (Diptera: Tachinidae) for the control of the European earwig (Forficula auricularia)

ABSTRACT The European earwig (Forficula auricularia) is an invasive species in the Falkland Islands, causing considerable problems for local horticulture, as well threatening indigenous ecosystems. To assess the potential of a classical biological control introduction two parasitoid fly species, Triarthria setipennis and Ocytata pallipes (Diptera: Tachinidae), were collected from sites in southern and northern England and then tested for their suitability as earwig biological controls at Egham, UK. Both species had previously been introduced into North America for earwig control however little is known of their long-term efficacy and host specificity. Host range tests including both target and non-target species were done. As there are no native Dermaptera on the Falkland Islands, tests were restricted to the field cricket Gryllus assimilis and the Dubia cockroach Blaptica dubia, as representatives of insect orders phylogenetically closely related to earwigs. A second cricket species (Gryllus bimaculatus) was included in an egg-depositing experiment for O. pallipes. Both tachinid species successfully parasitised and emerged from earwigs under laboratory conditions but no signs of parasitisation and development were observed in either the cricket or cockroach.

A baseline study using Plantwise information to assess the contribution of extension services to the uptake of augmentative biological control in selected low- to lower- middle- income countries

The uptake of augmentative biological control agents (BCAs) is still limited, particularly in many low- to lower- middle- income countries. This study focuses on factors that affect the uptake of BCAs for arthropod pests by national extension partners (NEPs) in Plantwise—an agricultural development programme facilitating the establishment of plant clinics where farmers can obtain diagnosis and plant health advice. Using data generated by NEPs, BCA recommendations in extension material and given by extension workers in Ghana, Kenya, Zambia, India, Nepal and Pakistan were analysed. The rate of BCA recommendation ranged from 13.0 (Zambia) to 61.1% (India) in extension materials and from 0.0 (Zambia) to 18.2% (India) in recommendations given by extension workers. Knowledge, availability and price were identified as the main factors affecting the uptake of BCAs by NEPs. This baseline study gives novel insight into the potential of NEPs to facilitate the use of BCAs.