(Coleoptera: Cerambycidae) is an emerging pest of sugarcane in South Africa. The larvae of this cerambycid beetle live within the sugarcane stalk and drill galleries that considerably reduce sugar ...production. To provide an alternative to chemical control, entomopathogenic nematodes and fungus were investigated as potential biological control agents to be used in an integrated pest management system. The nematodes
,
,
, and different concentrations of the fungus
were screened for efficacy (i.e., mortality rate) against larvae of
. The different biocontrol agents used, revealed a low level of pathogenicity to
larvae, when compared to control treatments.
A survey was undertaken to determine the diversity and frequency of endemic entomopathogenic nematodes (EPN) in subtropical regions in the Mpumalanga, Limpopo and KwaZulu-Natal provinces of South ...Africa. A total of 136 soil samples were randomly taken from cultivated and uncultivated habitats, including subtropical fruit tree orchards (avocado, litchi, macadamia, mango and guava) and adjoining natural vegetation. EPNs were isolated from 14 samples (10.3%) by means of baiting with Tenebrio molitor larvae. Heterorhabditis was the most common genus isolated from 12 samples, whereas only two Steinernema species were isolated. The most common Heterorhabditis isolated were Heterorhabditis noenieputensis and H. zealandica, which were both isolated from four samples each. The present report is the first occurrence of H. taysearae and H. baujardi in South Africa. The two Steinernema species are both unknown species. Laboratory bioassays were conducted to determine the potential of seven native EPN isolates to control the false codling moth (Thaumatotibia leucotreta) (FCM). Last instar FCM larvae were found to be most susceptible to S. yirgalemense (157-C), H. zealandica (WS 23) and Steinernema litchii (WS9), when exposed to 50 IJs/50 µℓ water for 48 h, causing 100%, 94.2% and 93.5% mortality, respectively.
Stacked wooden fruit bins are frequent overwintering sites for overwintering diapausing codling moth larvae. Control strategies against the codling moth (Cydia pomonella) (Lepidoptera: Tortricidae) ...in South Africa have been hampered by the reinfestation of orchards from nearby stacked infested fruit bins and by the movement of infested bins between orchards. Worldwide, wooden fruit bins are systematically being replaced with plastic bins, however in South Africa this will not be accomplished in the near future. The objective of this study was to evaluate the potential of two recycled commercially available entomopathogenic nematode (EPN) species, Heterorhabditis bacteriophora and Steinernema feltiae, as well as of a local species, Steinernema yirgalemense, to disinfest miniature wooden fruit bins under controlled conditions in the laboratory. After dipping miniature bins loaded with codling moth larvae in a suspension of 25 IJs/mL of each of the three EPN species, under optimum conditions of temperature and humidity, the highest percentage of control was obtained using S. feltiae (75%). The addition of adjuvants significantly increased S. feltiae infectivity to >95%, whereas it did not result in a significant increase in H. bacteriophora or S. yirgalemense infectivity.
Xenorhabdus
species are normally closely associated with entomopathogenic nematodes of the family Steinernematidae. Strain F2, isolated from
Steinernema nguyeni
, was identified as
Xenorhabdus ...bovienii
and strains J194 and SB10, isolated from
Steinernema jeffreyense
and
Steinernema sacchari
as
Xenorhabdus khoisanae
, based on phenotypic characteristics and sequencing of 16S rRNA and housekeeping genes
dnaN, gltX, gyrB, infB
and
recA.
All three strains produced antimicrobial compounds that inhibited the growth of Gram-positive and Gram-negative bacteria. This is the first report of associations between strains of the symbiotic bacteria
X. bovienii
with
S. nguyeni
, and
X. khoisanae
with
S. jeffreyense
and
S. sacchari
. This provides evidence that strains of
Xenorhabdus
spp. may switch between nematode species within the same clade and between different clades.
Infection of codling moth, Cydia pomonella (L.), larvae by the entomopathogenic nematode, Heterorhabditis zealandica, was studied under semi-field conditions. Late-instar diapausing codling moth ...larvae, coccooned in perforated cardboard strips, were used in all trials to evaluate the nematode treatments involved. A morning application of 0.5, 1.0 and 1.5 MM infective juveniles (IJs) per tree resulted in 85%, 95% and 100% codling moth larval infection, respectively. Contrasting results were obtained for an evening application, with low levels of codling moth infection (<50%). Nematode treatment strips placed in direct sunlight resulted in almost no infection (<10%), opposed to strips attaining 67% infection placed in the shade.
During a survey in the Mpumalanga province of South Africa, a Steinernema species was isolated from a soil sample taken from a litchi orchard. Steinernema litchii n. sp. can be separated from other, ...closely related, species in the glaseri-group by morphological, morphometric and molecular analyses. The infective third-stage juvenile of the new species has a body length of 1054 (953-1146) μm, distance from head to excretory pore of 78 (64-86) μm, as well as eight ridges (i.e., nine lines) in the mid-body region. The c-ratio of 10 (9-13) is low and the tail is long at 95 (73-105) μm. First generation males have a spicule length of 86 (76-96) μm and a gubernaculum length of 65 (59-72) μm. The tail of the first generation male lacks a mucron; that of the second generation always bears one. The genital papillae total 23 and consist of 11 pairs and an unpaired precloacal papilla. The vulva of S. litchii n. sp. has a slightly asymmetrical protuberance and short, double-flapped epiptygmata. The female has a slightly protuberant postanal swelling. Phylogenetic analysis of the internal transcribed spacer (ITS) and of the 28S (D2-D3) regions of the ribosomal DNA (rDNA) confirmed the close relationship of S. litchii n. sp. to the Karii-clade. Both morphological and molecular evidence support the species status of S. litchii n. sp.
Bacterial strain SF87T, and additional strains SF80, SF362 and 106-C, isolated from the nematode Steinernema khoisanae, are non-bioluminescent Gram-reaction-negative bacteria that share many of the ...carbohydrate fermentation reactions recorded for the type strains of recognized Xenorhabdus species. Based on 16S rRNA gene sequence data, strain SF87T is shown to be closely related (98 % similarity) to Xenorhabdus hominickii DSM 17903T. Nucleotide sequences of strain SF87 obtained from the recA, dnaN, gltX, gyrB and infB genes showed 96–97 % similarity with Xenorhabdus miraniensis DSM 17902T. However, strain SF87 shares only 52.7 % DNA–DNA relatedness with the type strain of X. miraniensis, confirming that it belongs to a different species. Strains SF87T, SF80, SF362 and 106-C are phenotypically similar to X. miraniensis and X. beddingii, except that they do not produce acid from aesculin. These strains are thus considered to represent a novel species of the genus Xenorhabdus, for which the name Xenorhabdus khoisanae sp. nov. is proposed. The type strain is SF87T ( = DSM 25463T = ATCC BAA-2406T).
The bacterial symbiont AM7T, isolated from a novel entomopathogenic nematode species of the genus Heterorhabditis, displays the main phenotypic traits of the genus Photorhabdus and is highly ...pathogenic to Galleria mellonella. Phylogenetic analysis based on a multigene approach (16S rRNA, recA, gyrB, dnaN, gltX and infB) confirmed the classification of isolate AM7T within the species Photorhabdus luminescens and revealed its close relatedness to Photorhabdus luminescens subsp. caribbeanensis, P. luminescens subsp. akhurstii and P. luminescens subsp. hainanensis. The five concatenated protein-encoding sequences (4197 nt) of strain AM7T revealed 95.8, 95.4 and 94.9 % nucleotide identity to sequences of P. luminescens subsp. caribbeanensis HG29T, P. luminescens subsp. akhurstii FRG04T and P. luminescens subsp. hainanensis C8404T, respectively. These identity values are less than the threshold of 97 % proposed for classification within one of the existing subspecies of P. luminescens. Unlike other strains described for P. luminescens, strain AM7T produces acid from adonitol, sorbitol and xylitol, assimilates xylitol and has no lipase activity on medium containing Tween 20 or 60. Strain AM7T is differentiated from P. luminescens subsp. caribbeanensis by the assimilation of N-acetylglucosamine and the absence of haemolytic activity. Unlike P. luminescens subsp. akhurstii, strain AM7T does not assimilate mannitol, and it is distinguished from P. luminescens subsp. hainanensis by the assimilation of trehalose and citrate, the inability to produce indole from tryptophan and the presence of acetoin production and urease activity. Strain AM7T ( = ATCC BAA-2407T = DSM 25462T) belongs to a novel subspecies, and is proposed as the type strain of Photorhabdus luminescens subsp. noenieputensis sp. nov.
Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), the obscure mealybug, is a serious pest of apples and pears in South Africa. The potential use of entomopathogenic nematodes (EPNs) ...against P. viburni was assessed in laboratory bioassays. The results showed Heterorhabditis zealandica (J34) to be most effective, causing 80% mortality of P. viburni 48-h post inoculation at 25 ºC. After 48 h, the LD
50
and LD
90
values were 54 and 336 nematodes, respectively. H. zealandica (J34) and Steinernema yirgalemense successfully reproduced in P. viburni, with H. zealandica (J34) attaining greater penetration ability than did the S. yirgalemense. Mealybug size affected infectivity, with the crawlers being less susceptible (22%) than were the adults and intermediates, with mortalities of 78% and 76%, respectively. H. zealandica (J34) were able to enter the apple core of infested apples, where they infected the P. viburni. This work represents the first report on using EPNs to control P. viburni.
The potential of entomopathogenic nematodes,
Heterorhabditis bacteriophora,
Heterorhabditis zealandica and
Steinernema khoisanae, to infect pupariating larvae, pupae and adults of
Ceratitis capitata ...and
Ceratitis rosa was investigated in laboratory bioassays. Pupariating larvae and adult flies were susceptible to nematode infection, with no infection recorded for the pupae. Pupariating larvae of
C. capitata were generally more susceptible to infection than those of
C. rosa. Significantly more larvae of
C. capitata were infected by
H. bacteriophora. For
C. rosa, highest infectivity of larvae was obtained with
H. zealandica. In contrast, adults of both species were highly infected by
S. khoisanae.
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