Abstract
Numerous nematodes in the genus
Oscheius
possess entomopathogenic abilities. These nematodes also kill their insect hosts by releasing their symbiotic bacteria within 48–72 h. In this study, ...12 indigenous isolates of
Oscheius myriophilus
based on molecular, morphological, and morphometric studies were recovered from different undisturbed soils in Thailand. Moreover, the virulence of 12
O. myriophilus
at a rate of 25 IJs/cm
2
against fifth‐instar larvae of
Galleria mellonella
ranged from 56%–86% after 72 h of exposure.
Oscheius myriophilus
EPNKU40 exhibited the highest efficacy in causing mortality in the insect larvae. It also killed third‐instar larvae of
Spodoptera litura
and
Spodoptera exigua
up to 60% after 72 h of exposure. The median lethal concentration (LC
50
) values of
O. myriophilus
EPNKU40 against
G. mellonella
larvae after 48 and 72 h of exposure were 11 and 4 IJs/cm
2
, respectively. The discovery of
O. myriophulus
is the first record in Thailand characterized using morphological, morphometric, and molecular diagnostic tools, which have shown lethal effects against insect pests and can later be utilized as biocontrol agents after several comprehensive assessments.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The cosmopolitan terrestrial slug, Deroceras laeve (O. F. Müller, 1774), is reported in the Philippines for the first time and characterized through morphology, morphometrics, and cytochrome oxidase ...subunit I (COI) gene analysis. Slug samples were recovered from two administrative regions in Mindanao, Philippines. In Region X, there were two sites: Misamis Oriental (Gingoog, 664 m a.s.l.; Claveria, 937 m a.s.l.) with farms planted with cabbage ( Brassica oleracea ), radish ( Raphanus sativus) , and eggplant ( Solanum melongena ); and Bukidnon (Talakag, 1410 m a.s.l.) planted with cabbage. In Region XI, specimens were collected from potted ornamentals in five nurseries along the Kapatagan road, Davao del Sur, 1000-1200 m a.s.l. The external morphology of the specimens matched the published descriptions, and their identity was further confirmed by their partial COI sequences. The obtained COI sequence of the specimen in Region X showed 99-100% similarity with the voucher specimens from Mexico (KX959495, KX959496, KX959497, KX959498, and KX495499); while that of the specimen from Region XI is 100% identical to specimens collected from Japan (MW507142), Canada (MT680918 and MT941436), UK (KF894311), and Vietnam (MT941435 and MT941436). Moreover, D. laeve from Region X and Region XI shared 98% similarity with each other. Preliminary surveys show that slug occurrence is prevalent mainly in highland regions of the southern Philippines where specialty crops/high value crops like vegetables and ornamentals are cultivated. Further surveys are essential to confirm any damage that they may cause, their distribution, associated parasites, and pest status in the Philippines.
Background
Entomopathogenic nematodes of the genera
Heterorhabditis
and
Steinernema
are widely used as biocontrol agents against diverse insect pests. Their association with symbiont bacteria is ...found to be the primary cause of insect mortality. The present study reported a comprehensive characterization of a local Philippine EPN isolate using congruent morpho-taxometrical and molecular data and the associated bacterium in the infective dauer juveniles.
Results
Using an insect-baiting technique, a nematode isolate labeled F2H was recovered from the sandy soils in the coastal area of southern Philippines. Based on morphology and morpho-taxometrics, the F2H isolate collected from Iligan City was identified as
Heterorhabditis indica
. Analysis of the ITS region of rDNA revealed the highest sequence match to
H. indica
. The sequences of the bacterial 16S rDNA gene showed that the symbiont of
H. indica
presented 100% similitude with the sequences of
Ochrobactrum anthropi
. Further, pairwise alignment and phylogenetic analysis demonstrated that
O. anthropi
,
O. lupini
and
O. cytisi
shared 100% similarity and form a monophyletic clade. These strains have not presented any differences in the phylogenetic and 16S rDNA data, and
O. lupini
and
O. cytisi
should be considered a later heterotypic synonym of
O. anthropi
.
Conclusions
The description of
H. indica
-
O. anthropi
association was the first report in the Philippines. This provides additional account and collection of naturally isolated EPN-bacteria, contributing to limited knowledge on its diversity in the Philippines, which can be utilized in the biocontrol of pests after further comprehensive assessments.
Background
The tobacco cutworm,
Spodoptera litura
Fab. (Lepidoptera: Noctuidae), is a devastating insect pest of several crops. Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and ...Steinernematidae are used as an alternative control measure in lieu of the hazardous synthetic chemical applications.
Results
A survey of naturally occurring EPNs was conducted across the province of Cotabato, Philippines, covering a total of 5 municipalities with 25 villages.
Galleria
-baiting technique was employed to recover nematodes from peanut and grassland soils. Out of 50 soil samples collected, only 5 samples harbored nematodes, indicating a recovery of 10%. Preliminary morphological data identified only one EPN under the genera
Heterorhabditis
(1 isolate), whereas 4 were facultative necromenic nematodes from the genera
Metarhabditis
(2 isolates) and
Oscheius
(2 isolates). Analysis of D2D3 segments of the 28S rDNA confirmed high sequence similarity to
Heterorhabditis indica
,
Metarhabditis rainai
,
Oscheius insectivora
, and
Oscheius
sp. This is the first record of
H. indica
and
M. rainai
in the entire region, whereas the first record for
Oscheius
spp. in the Philippines. Furthermore, the biocontrol potential of the local
H. indica
infective juvenile (IJ) populations (PIGCD1) isolated from peanut was assessed against the tobacco cutworm,
S. litura
, under laboratory conditions. The mean percentage mortality caused by
H. indica
on
S. litura
at 7 different concentrations ranged from 0-100% at 24 h post inoculation. The lethal concentration (LC
50
) required to kill 50% of the
S. litura
larvae population with
H. indica
was 7.13±1 (IJs/larva).
Conclusions
The use of
Galleria
-baiting method is a convenient approach to detect EPNs including other facultative necromenic nematodes from the soils. Obtained data indicated that the local
H. indica
isolate can be a promising alternative measure to suppress the economically important insect pest,
S. litura
, and this may provide significant outlook to establish the biocontrol program in the country.
Herein, we first report the comprehensive description of the terrestrial slug, Sarasinula plebeia (Gastropoda: Veronicellidae) by employing morphology, morpho-taxometrics and molecular analysis. A ...rapid survey on terrestrial slug invasive alien species (IAS) was conducted in La Dicha, Malangas, Zamboanga Sibugay, the Philippines. Obtained COI gene sequences shared 100% similarities to S. plebeia from Brazil (JX532107, KM489378), Dominica (KM489500) and Vietnam (KM489367) and further supported using Bayesian analysis thus designated as S. plebeia isolate LDZS. Notably, the first reported S. plebeia in 2013 from Batan island, Batanes, northern Philippines, characterized through COI gene markers (JQ582277, JQ582278, JQ582279) showed 100% sequence similarities to a closely related veronicellid slug, Laevecaulis alte isolates (LC636101, LC636102, LC636103, and LC636104) from Japan. Taken this into account, our S. plebeia LDZS isolated from an agricultural field is the first report in the Philippines with combined diagnostic tools for the taxon.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Background
Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae are used as biological control agents of several insect pests in lieu of synthetic pesticides.
...Results
Using an insect-baiting technique, naturally occurring EPN isolates were collected from banana and rice fields in the municipality of Hagonoy, the Philippines. A total of 4 isolates were recovered from all the sites namely, HBP1, HBP2, HR3 and HR4. By combining morphometrical and ITS rDNA data, all the isolates were identified as
Heterorhabditis indica
. To initially assess their infectivity, virulence tests were conducted on the last instar larvae of the super worm,
Zophobas morio
Fabricius (Coleoptera: Tenebrionidae), the model insect. HR3 isolate had the highest percentage mortality (56%), followed by HBP1 and HBP2 (33%), which were comparable to the available nematode in the market,
Heterorhabditis bacteriophora
(44%), whereas the lowest was obtained in HR4 isolate (11%).
Conclusions
This study accounted 4 more
H
.
indica
isolates in addition to pre-existing isolates in the country, expanding its habitat range and geographic distribution. This also provides baseline information on the potential biocontrol utilization of native EPNs against soil-dwelling insect pests of agricultural crops. Further investigations are required to assess their efficacy against several other insect pests of economic importance for the integrated pest management (IPM) programmes in the country.
Background
Trichoderma asperellum
(Ascomycota: Hypocreaceae) is a globally recognized soil fungus due to its broad-spectrum antimicrobial and plant growth-promoting properties. To increase the ...availability of local strains, soil samples from a dragon fruit farm in Villanueva (Misamis Oriental, Philippines) were collected and baited using the insect-baiting technique.
Results
Using the baiting technique,
T. asperellum
strain, RMCK01, was isolated. The strain was characterized using morphological and molecular data and its biological control potential was tested using different conidial concentrations on the last larval instar of the super worm,
Zophobas morio
(Fabricius, 1776) (Coleoptera: Tenebrionidae). The ITS1 sequences of
T. asperellum
RMCK01 were 100% identical to the sequences of other
T. asperellum
isolates reported from Vietnam, India, Thailand, and China. In addition,
T. asperellum
RMCK01 was particularly efficient against
Z. morio
larvae
.
On day 21, 88.87%, 88.07%, and 86.73% of insects died when treated with a suspension containing 6 × 10
8
, 3 × 10
9
, and 2.68 × 10
7
conidia/ml, respectively.
Conclusion
The study highlights the potential of this fungal isolate as a biocontrol agent against insect pests.
A new species of the genus Synoecnema-S. watinagii sp. n.-is described and illustrated. The species is characterized by its small size, lack of sexual dimorphism apart from sexual characters, males ...with pericloacal disk, females with anterior vulva position and lacking an anus, and similar caudal organs in both sexes in the shape of long, deep slits on the surface of the posterior half of body. Sequences of D2-D3 LSU and SSU rDNA and SEM images were obtained for the first time for the genus Synoecnema. Phylogenetic analysis of these sequences supported the validity of the genus and elucidated its relationships within Synoecneminae and Drilonematoidea. The earthworm host was characterized by its CoxI mt DNA sequence.
The common cutworm, Spodoptera litura, is a serious insect pest of many vegetables and crops worldwide. Entomopathogenic nematodes (EPN) have been utilized as biological control agents for ...controlling various insect pests, including the larvae of S. litura. Many indigenous EPN have been recognized to be more effective in specific field applications. Among the 160 soil samples collected in undisturbed areas of western Thailand, three samples tested positive for EPN. Three indigenous EPN were identified as Steinernema siamkayai namely, EPNKU63, EPNKU70 and EPNKU85, based on ITS and D2/D3 expansion region analysis of the 28s rRNA genes. Additionally, genetic analysis of the symbiotic bacteria using recA rRNA sequences confirmed their identity as Xenorhabdus stockiae namely, PEPNKU63, PEPNKU70 and PEPNKU85. To evaluate their initial biocontrol potential against the 6th instar larvae of Galleria mellonella, virulence assays were conducted. The application of 100 infective juveniles (IJs)/insects resulted in the mortality of 80–100% of G. mellonella larvae after 72 h. When symbiotic bacteria were applied at 1 × 106 cells/insect, they exhibited 63–93% mortality against G. mellonella larvae after 120 h. In further laboratory tests, three S. siamkayai isolates achieved 100% mortality of 3rd instar Spodoptera litura larvae within 72 h, with LC50 values ranging from 29 to 30 IJs/insect. In screenhouse experiments, it was revealed that all S. siamkayai isolates displayed substantial virulence, ranging from 62% to 74%, against 3rd instar S. litura larvae within 72 h. This study demonstrates the biocontrol potential of S. siamkayai in controlling S. litura larvae.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
PDF
