The authors discuss the first record and molecular identification of root-knot nematodes from honeybush tea plants (Cyclopia spp.) in South Africa. Honeybush is an indigenous Cape fynbos legume plant ...that is a rich source of antioxidants and possesses antimutagenic properties. Root-knot damage on tea crops has been reported caused by root-knot nematode (RKN), a problem threatening the budding local industry. The results of the molecular study confirmed the presence of M. hapla and M. javanica, both being pathogenic to honeybush and with the ability to cause serious damage to the plants concerned and economic loss. In Africa, RKN have been described as posing a major threat to food security. The results of the current study also indicate that the high numbers of nematodes contributed to the reduced yield of honeybush and this could be a potential threat to the herbal tea industry.
False codling moth,
Thaumatotibia leucotreta
(Meyrick) (Lepidoptera: Tortricidae), is an important pest of fruit trees in South Africa. The subtropical fruit tree crop industries use a combination of ...techniques for
T. leucotreta
suppression. Semi-field trials were conducted in avocado, litchi and macadamia orchards, using four entomopathogenic nematode (EPN) species. The effect on
T. leucotreta
mortality, directly after application (two days), as well as on persistence for 7, 14, 21, 28, 35, and 42 days post-application, was determined. Results from the field trials, using 30 IJs cm
2
of
Steinernema yirgalemense
, showed the highest mortality of 86% directly after application, with
Steinernema litchii
being the least effective of the four EPN species, with 63% mortality. High persistence was found until day 14, with a steep decline thereafter until day 28. Local South African EPN species showed great potential for the future control of the late instar
T. leucotreta
, with the added advantage of persistence.
Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis have demonstrated great potential as useful bio-control agents in the management of certain important soil-inhabiting ...insect pests of agricultural crops. In a survey of nematodes associated with organic honeybush cultivation, soil samples were obtained from nine organic honeybush plots, which are located in the Bredasdorp area of the Western Cape province of South Africa. The EPNs were isolated from soil by baiting with larvae of Galleria mellonella (greater wax moth) and identified by the amplification of the internal transcribed spacer region using the primer set TW81 and AB28. EPNs were abundant in the honeybush orchards, accounting for about 50% of the sampled fields and five EPN species were identified including Heterorhabditis bacteriophora, Heterorhabditis safricana, Steinernema khoisanae,. Steinernema nguyeni, Oscheius sp. and an unknown EPN, therefore suggesting a substantial diversity of EPNs in the sampled fields. A 100% mortality of infected G. mellonella larvae was recorded within 48 h of exposure to the nematodes. However, although these EPNs have been previously reported in South Africa, it is the first time they are found in such diversity on a conservative tillage management system in organic honeybush cultivation.
Summary
In the period from August to October 2018, 140 specimens of the Spanish slug, Arion vulgaris, were collected from Podbrezje, Slovenia. Slugs were dissected and examined for the presence of ...parasitic nematodes within the cadavers. Identification of the nematodes was conducted using morphological and molecular techniques and confirmed the presence of Phasmarhabditis papillosa. This is the first record of P. papillosa from the mollusc host, A. vulgaris. Laboratory experiments aimed at testing the efficacy of P. papillosa against A. vulgaris were conducted using nematodes grown in vivo. Nematodes were applied at concentration rates of 50, 100 and 200 nematodes slug−1, respectively. Three weeks following treatment, the mortality of slugs was confirmed in all treatments (50 nematodes slug−1, 37.4 ± 2.7%; 100 nematodes slug−1, 48.4 ± 2.7%; 200 nematodes slug−1, 50.6 ± 2.7%). However, the pathogenesis of P. papillosa was observed first in the treatments with the lowest nematode dose at 4 days after treatments, while a decrease in the feeding behaviour of slugs was noted first in the treatments with the highest nematode dose. Future opportunities for the potential use of P. papillosa as a biological control agent against slugs are discussed. This is the first report of P. papillosa from Slovenia, and of its virulence against A. vulgaris.
Phlyctinus callosus (Schönherr), the banded fruit weevil, is a key pest of deciduous fruit and grapevine in the Western Cape province of South Africa. Entomopathogenic nematodes (EPNs), as a ...biocontrol agent, are found to be effective in controlling both soilborne and above‐ground insect pests. Different EPN species were screened for virulence against different life stages of P. callosus, followed by a field trial, in which Steinernema yirgalemense was applied at different concentrations. S. yirgalemense, Heterorhabditis noenieputensis and the exotic Steinernema feltiae gave good control of P. callosus larvae at 100 infective juveniles per insect, with no significant difference between treatments. In the case of P. callosus pupae, Heterorhabditis indica (70%) and Heterorhabditis baujardi (67%) differed significantly (P < 0.05) in their control, compared with H. noenieputensis (55%). H. indica (95%) and S. yirgalemense (94%) gave significantly higher (P < 0.05) control of P. callosus adults, compared with the three other nematode species tested. In the field trials, S. yirgalemense, at 20 and 40 infective juveniles/cm2, gave 69% and 78% control of P. callosus larvae after 48 h of exposure, respectively. The results indicated that all EPNs tested were effective against the immature and adult stages of P. callosus, with differences in mortality among the EPN species tested. S. yirgalemense, at low concentration, can effectively control P. callosus under field conditions, but large‐scale field trials are recommended to demonstrate the potential use of this biocontrol agent within integrated pest management programmes.
Nematodes are important soil organisms that constitute a key component of the soil ecosystem. A plant-parasitic survey was conducted to identify the diversity of nematodes associated with two endemic ...tea plants, honeybush (Cyclopia spp.) and rooibos (Aspalathus linearis) in the Western Cape province of South Africa. A total of 20 farmlands were surveyed and soil samples were collected from the rhizosphere of plants, for nematode isolation and identification based on morphological characters. Confirmation of the species of plant-parasitic nematodes was done using molecular-based tools. Nematodes were classified into various feeding groups based on their colonizer-persister (c-p) values. Plant-feeding nematodes identified from the honeybush tea plants include; Criconema mutabile, Meloidogyne hapla, M. javanica, and Xiphinema oxycaudatum, while Hoplolaimus sp., Neodolichorhynchus estherae and Pratylechus bolivianus were pathogenic on the rooibos monocultures. Bacterial and fungal feeders (Cephalobidae and Rhabditidae) were also abundant and frequently encountered in all samples. The study provides information on the diversity of nematodes associated with the indigenous herbal tea plants of South Africa.
Colonizers; Maturity indices; Morphological identification; Molecular identification; Soil ecosystem.
The occurrence and diversity of entomopathogenic nematodes (EPN) and their symbiotic bacteria was evaluated in commercial forestry plantations (Eucalyptus spp., Pinus spp. and Acacia mearnsii) and ...indigenous forests in South Africa. EPN were most prevalent in A. mearnsii plantations, accounting for 60.7% of the isolates, while indigenous forests, plantations of Pinus spp. and Eucalyptus spp. accounted for 35.7, 3.6 and 0% of the isolates, respectively. DNA sequences of the internal transcribed spacer (ITS) and D2-D3 28S rDNA regions were used to identify the nematode species. Four Steinernema spp. were identified, including S. citrae, S. sacchari, two undescribed species, as well as Heterorhabditis bacteriophora and H. baujardi. Heterorhabditis baujardi is reported from South Africa for the first time. Analysis of 16S rRNA of the bacteria confirmed the presence of at least three Xenorhabdus species from Steinernema isolates and two subspecies of Photorhabdus luminescens from Heterorhabditis species.
The bacterial symbionts SF41T and SF783 were isolated from populations of the insect pathogenic nematode Heterorhabditis zealandica collected in South Africa. Both strains were closely related to ...strain Q614 isolated from a population of Heterorhabditis sp. collected from soil in Australia in the 1980s. Sequence analysis based on a multigene approach, DNA-DNA hybridization data and phenotypic traits showed that strains SF41T, SF783 and Q614 belong to the same species of the genus Photorhabdus with Photorhabdus temperata subsp. cinerea as the most closely related taxon (DNA-DNA hybridization value of 68%). Moreover, the phylogenetic position of Photorhabdus temperata subsp. cinerea DSM 19724T initially determined using the gyrB sequences, was reconsidered in the light of the data obtained by our multigene approach and DNA-DNA hybridization experiments. Strains SF41T, SF783 and Q614 represent a novel species of the genus Photorhabdus, for which the name Photorhabdus heterorhabditis sp. nov. is proposed (type strain SF41T=ATCC BAA-2479T=DSM 25263T).
Worldwide interest in Phasmarhabditis originates from the successful commercialisation of P. hermaphrodita as a biological control agent against molluscs in Europe. To date, P. hermaphrodita has not ...been isolated from South Africa and, therefore, the formulated product may not be sold locally. During a survey for mollusc-associated nematodes, P. papillosa was dissected from the slug, Deroceras reticulatum, collected from George, South Africa. The nematode was identified using a combination of morphological, morphometric, molecular and phylogenetic techniques. Virulence tests were conducted which demonstrated that P. papillosa caused significant mortality to the European invasive slug Deroceras panormitanum. Additional data are provided in the morphometrics of the infective juvenile and in the molecular identification, using the mitochondrial cytochrome c oxidase subunit I (cox1) gene. This is the first report of P. papillosa from the African continent and of its virulence against D. panormitanum.
Strain WS9, a mutualistic-associated bacterium, was isolated from an unknown entomopathogenic Steinernema nematode, collected from a litchi orchard in Friedenheim, Mpumalanga, South Africa. Based on ...phenotypic and phylogenetic data of the 16S rRNA, gltX, recA, dnaN, gyrB and infB gene sequences, strain WS9 is identified as
X. griffiniae
. Strain WS9 has antibacterial activity against Gram-positive and Gram-negative bacteria. This is the first report of an association between
X. griffiniae
and an unknown
Steinernema
species from South Africa.
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