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El-Ashry and Abd El-Aal
Egypt. J. Agronematol., Vol. 18, No.2 (2019)
Evaluation of Certain Egyptian Heterorhabditids Isolates as Molluscicidal
Nematodes for The Control of Deroceras reticulatum and D. leave Slugs
under Laboratory Conditions.
El-Ashry, R. M. and E. M. Abd El-Aal
Dept. Plant Protection, Fac. Agric., Zagazig University, Egypt.
Corresponding author email: mrmaa2010@yahoo.com
:
ABSTRACT
:
Deroceras laeve Müller and D. reticulatum Müller are serious slugs of field crops in Egypt.
Chemical control using metaldehyde baits is still the main control tactic. In 2018, a survey of
terrestrial slugs at Belbis district, Sharkia Governorate, Egypt failed to find the
molluscicidal nematode, Phasmarhabditis hermaphrodita. Dead slugs produced only
free-living or non pathogenic nematodes belong to Family Rhabditidae. Two imported
EPNs species; Steinernema carpocapsae (All strain) and Heterorhabditis bacteriophora
(HP88 strain) were screened for molluscicidal activity against D. laeve and D.
reticulatum compared with three Egyptian Heterorhabditis isolates, Ht strain, Ar-4 strain
and Serag1 strain. S. carpocapsae (All strain) and H. bacteriophora (HP88 strain),
showed promising results by killing territorial slugs. S. carpocapsae (All strain)
resulted in the greatest percentage mortalities 100% in D. laeve and D.reticulatum after
14 days at a concentration of 2000IJs/cm whereas, the application of H. bacteriophora
(HP88 strain) induced percentages mortality 50 and 66.67% with D. laeve and D.
reticulatum, respectively. The Egyptian strain H. bacteriophora showed less
molluscicidal activity against the two tested slugs. After 14 days, D. reticulatum
mortalities were 36.67, 40.00 and 46.33 % by the application of H. bacteriophora
(Serag1 strain), H. bacteriophora (Ht strain) and H. bacteriophora (Ar-4 strain),
respectively. Whereas, the percentage mortalities were 20.00, 23.33 and 26.67 % ; 10.00,
13.33 and 13.33% in D. leave at low concentrations (1000 IJs/cm2 & 500 IJs/cm2),
respectively. Egyptian isolates showed less encourage usage as a specific biological
control agent against D.laeve and D.reticulatum compared to S. carpocapsae (All strain)
and H. bacteriophora (HP88 strain).
Finally, results of this study indicate the need to an extensive survey in all Egypt to
detect and isolate the slug parasitic nematode, P. hermaphrodita as it was recorded in
Dakahlia governorate infesting different snails and slug species and research should
proceed to find virulent isolates from EPNs to control terrestrial slugs.
Keywords: Survey, Biological control, Deroceras laeve, D. reticulatum, Heterorhabditis
bacteriophora, Steinernema carpocapsae.
INTRODUCTION
Slugs belong to Mollusca, Gastropoda cause considerable damage to field crops,
vegetables, fruit trees, ornamental plants, landscapes, nurseries and greenhouses
(Kaya, 2001). Slugs may also pose a health threat to humans, pets, and wildlife by
Evaluation of Certain Egyptian heterorhabditids Isolates….
72
Egypt. J. Agronematol., Vol. 18, No.2 (2019)
serving as intermediate hosts for many vertebrate parasites (e.g., lungworm) (South,
1992).
In Egypt, land gastropods could be considered as dangerous crop pests and cause
considerable damage to the majority of economic crops. The increased pest status of
these species differed from place to another, depending on food supply and weather
conditions especially in moist areas where they find the optimum conditions for rapid
multiplication (Kassab and Daoud,1964; El-Okda, 1980 and El-Deeb et al.,1996, 2003).
Theenhaus and Scheu (1996) showed that many of slug species do not pose a risk to
plant, human or veterinary health; indeed, they can play a role in nutrient cycling and
ecological diversity. On the other hand, numerous slug species cause considerable
amounts of economic damage in field crops especially in damp, mild climates (Barker,
2002).
Current control options include chemical, cultural and biological approaches.
Molluscicides based on baits containing metaldehyde and methiocarbas active
ingredients dominate chemical control products (Glen and Moens, 2002&Abd El-Aal,
2007), have proven to be effective when properly used. These materials are the most
widely used for slug control. However, under cool and wet conditions when slugs are
most active and troublesome, the slugs can often recover (Ohlendorff, 1998). In addition,
these chemical baits are toxic, posing health concerns for children, pets, and wildlife.
Furthermore, there are environmental objections to the use of molluscicidal chemicals.
Consequently, an integrated strategy is usually required and new developments will be
crucial to maintain and improve the existing levels of control.
With respect to pest slug management, although natural enemies of mollusks have
been known for many years (Runham and Hunter, 1970), their wide-scale potential as a
control solution has not been subject to intensive research activity until the last 30–50
years, in large part because of the dominance of the agrochemical industry. The parasitic
nematode Phasmarhabditis hermaphrodita (Schneider) is the most widely established,
commercially available slug biocontrol agents in Europe and is currently sold as the
proprietary product Nemaslug1(Wilson et al.,1993). Nemaslug1 is effective against
adults and juveniles of nine pest slug species and solely juveniles of two species (Rae et
al., 2007). Notable exceptions include Limax maximus and the Arion slugs, A. hortensis
and Arion subfuscus, which are not susceptible.
Although P. hermaphrodita was discovered almost 155 years ago (Schneider, 1859), it
was not until it was isolated again in the UK in 1988 that its potential as a slug biocontrol
agent was recognized (Wilson et al., 1993), and it was later shown to be associated
symbiotically with the bacterium Moraxella osloensis (Bevre &Henrikson) (Tan and
Grewal, 2001; 2002; 2003). A number of snail species has been shown to be susceptible
to P. hermaphrodita (Rae et al., 2007), which reflects the similarities in their anatomy
and biology. Despite the known parasitic relationships between a range of slug and
nematode species (Morand et al., 2004), P.hermaphrodita was the first nematode actually
shown to kill slugs (Wilson et al., 1993; Pieterse et al., 2017 & Nermut and Puza, 2017 ;
Askary et al., 2017).
Certain strains of the entomopathogenic nematodes, Steinernema carpocapsae, S.
feltiae and Heterorhabditis bacteriophora have also been tested in bioassays, but positive
results reported by Jaworska (1993) could not be replicated elsewhere (Wilson et al.,
1994). Host range experiments have shown that P. hermaphrodita is effective against a
wide variety of economically important pest slug and snail species (Coupland, 1995;
Wilson and Gaugler, 2000; Glen and Coupland, 2017;Tandingan et al., 2017)
El-Ashry and Abd El-Aal
Egypt. J. Agronematol., Vol. 18, No.2 (2019)
Therefore, the aim of present study is to conduct a survey for molluscicidal nematodes
at Belbis district, Zagazig, Egypt and evaluate the efficacy of three local strains of
entomopathogenic nematode, Heterorhabditis bacteriophora (Ar-4, Serag1and Ht strains)
isolated from EL-Arish and Giza Governorates, Egypt and two imported nematode
species, Steinernema carpocapsae (All strain) and H.bacteriophora (HP88strain) for the
control of two terrestrial slugs (Deroceras leave Müller,1774 and D. reticulatum
Müller,1774) under laboratory conditions.
MATERIALS AND METHODS
1- Survey studies
A survey study for collecting molluscicidal nematodes was conducted throughout
slug-prone areas (fruit trees, mandarin, navel orange, guava orchards,mango trees and
ornamental plants, hibiscus, magnolia, rose trees)of Basateen Serag El-Dein locality,
Belbies district. Slug collection was accomplished mainly through sight inspection of
groundcover. Refuge traps were used to collect current slug species (Abd El-Aal,2001). It
is simply consisted of lengths (15 cm x 20 cm) of damp wood placed adjacent to slug
infested areas. The slug species collected are the field (gray garden) slug, Deroceras
laeve Müller and D. reticulatum Müller .
The collected slugs were kept in 640 cc plastic containers with moist cotton cloth
inside coolers maintained below 20°C, until transported back to Agricultural Zoology
Laboratory in Plant Protection Department, Faculty of Agriculture, Zagazig University,
Egypt where this work was conducted. Captured slugs were placed in large plastic
containers (30 x 25 x 13 cm) lined with moist sterile sandy soil, provided daily with
lettuce as food, and observed for signs of nematode infection (swollen mantle) for a
period of more than two weeks. Declining slugs were placed in White traps (Kaya and
Stock 1997) to collect any emerging dauer juvenile nematodes. The healthy slugs were
maintained in the plastic containers for future use in bioassays. Nematodes isolated from
the survey were tested with Koch’s Postulates to determine pathogenicity.
2- Isolation, rearing and preparing of native entomopathogenic nematodes (EPNs):
EPNs were collected, reared and prepared as described by EL-Ashry et al., 2018. The
original method described by Dutky et al.(1964) was used with some modifications,
where the dead larvae were placed on a special fabric muslin cloth to avoid the
disintegration of the filter papers. Nematode juveniles were maintained in 0.1%
formaldehyde until identification. Three isolates designated as H.bacteriophora (Ar-
4strain) from EL-Arish, H. bacteriophora (Serag1strain) from Belbies and
H.bacteriophora (Htstrain) from Giza were extracted from soil samples.
3- Molluscicidal activity of native and imported entomopathogenic nematodes:
EPNs were screened for molluscicidal activity against two common pest slug species, D.
reticulatum and D. laeve. The following experimental design was used for all bioassays.
Plastic boxes (10 x15x 6cm) were lined on the inside walls with copper tape to prevent
the slugs from moving to the lid and still in contact with the nematodes. Five small
ventilation holes were made in the lids, and the plastic cages were filled with 10 g of
sterile sand. Nematode infective juvenile (IJ) suspensions were concentrated to the
desired concentrations (2000 IJs/cm2, 1000 IJs/cm2 and 500 IJs/cm2) and applied directly
to the soil surface in 1.5 ml of water.
Evaluation of Certain Egyptian heterorhabditids Isolates….
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Egypt. J. Agronematol., Vol. 18, No.2 (2019)
To insure optimum pathogenicity, only less than 2 weeks old IJ cultures were used in
the bioassays. The control treatment consisted of 1.5 ml of distilled water. Every plastic
cage contained a single, healthy slug. Slugs were fed daily on one lettuce disc (3.5 cm
diameter) and replaced every 48 h. Moisture was adjusted as needed. The experiment was
maintained at laboratory temperature (22º ± 3C), and slug mortality was monitored daily
for two weeks. Slug cadavers were placed in White traps to recover any emerging
nematodes.
Each screening or treatment consisted of three replicates consisting of 10 slugs for each
nematode species or strain. Mortality percentages were calculated according the
following formula:
100
slugs ofnumber Total
slugs dead ofNumber
(%)Mortality
4- Statistical analysis:
The experiments were carried out in a completely randomized design with 3
replications for each treatment. Data were subjected to analysis of variance (ANOVA)
using MSTATversion4 (1987).Means were compared by Duncan’s multiple range test
(Duncan, 1955) at P ≤ 0.05
RESULTS AND DISCUSSION
1- Survey of terrestrial slugs and molluscicidal nematodes at Belbis district, Sharkia
Governorate:
An extensive survey was carried out during two successive years started from January,
2016 to December, 2017 to obtain basic information’s concerning occurrence of
terrestrial slugs in 35 localities (villages) at Belbis district (county) of Sharkia
Governorate . The two gray field slug species, Deroceras reticulatum and D.laeve were
collected at some given site, but, D. reticulatum was usually the dominant one. Collected
slugs were observed carefully for signs of nematode infection (swollen mantle). Slug
cadavers placed on White traps and Koch’s Postulates were followed. Isolated nematodes
were non-pathogenic. Survey of terrestrial slugs at Belbis district failed to find the
molluscicidal nematode, P. hermaphrodita. The slug parasitic nematode, P.
hermaphrodita was recorded in Egypt in Dakahlia governorate associated with different
snail and slug species i.e. Monacha cantiana, Eobania vermiculata, Helix aspersa and
Lehmania marginata. (Genena et al., 2011).
2- Pathogenicity of imported EPNs and local isolates of Egyptian Heterorhabditis
bacteriophora isolates against Deroceras leave and D. reticulatum:
Three Egyptian Heterorhabditis isolates were screened for molluscicidal activity
against D. leave compared with two imported species, S. carpocapsae (All strain) and
H. bacteriophora (HP88 strain) after different periods of exposure. Both S.
carpocapsae (All strain) and H. bacteriophora (HP88 strain), at the highest
concentration (2000 IJs/cm2) showed promising results by killing 100% and 50 %
of territorial slug, D. leave after 14 days of exposure, respectively. (Table 1). At
low application rates, 1000IJs/cm2and 500IJs/cm2, percentage mortalities decreased
to 70.00, 43.33; 43.33, 26.67 % with S. carpoapsae (All strain) and
H.bacteriophora (HP88 strain), after 14 days of exposure, respectively.
El-Ashry and Abd El-Aal
Egypt. J. Agronematol., Vol. 18, No.2 (2019)
Whereas, the three strains of Egyptian H. bacteriophora , H. bacteriophora (Serag1
strain), H. bacteriophora (Ht strain) and H. bacteriophora (Ar-4 strain) showed less
effectiveness as molluscicidal activity against D.laeve slug. At concentration of 2000
IJs/cm2, percentage mortalities in D. leave ranged from 26.33 to 30.00 % by the
application of H. bacteriophora (Serag1 strain) , H. bacteriophora (Ht strain) and H.
bacteriophora (Ar-4 strain).
Table 1. Molluscicidal activity of Egyptian Heterorhabditis strains against the gray slug
Deroceras laeve compared with Steinernema carpocapsae (All strain) and
Heterorhabditis bacteriophora (HP88 strain) after different periods of exposure.
Nematode species
Conc.
Deroceras leave
Mean percent mortality %
6 days
10 days
14 days
S. carpocapsae (All strain)
2000 IJs/ cm2
56.67 a
83.33 a
100.0 a
1000 IJs/cm2
36.67 a
60.00 a
70.00 a
500 IJs/cm2
6.67 de
16.67 c
43.33 b
H. bacteriophora (HP88
strain)
2000 IJs/ cm2
26.67 b
43.33 b
50.00 b
1000 IJs/cm2
20.00 b
30.00 b
43.33 b
500 IJs/cm2
6.67 de
16.67 c
26.67 bc
H. bacteriophora (Serag1
strain)
2000 IJs/ cm2
6.67 de
16.67d
26.33 cd
1000 IJs/ cm2
6.67 de
10.00 cd
20.00 c
500 IJs/ cm2
0.00 f
10.00 cd
10.00 d
H. bacteriophora (Ht strain)
2000 IJs/ cm2
6.67 de
13.33 d
26.67 bc
1000 IJs/ cm2
6.67 de
13.33 c
23.33 cd
500 IJs/ cm2
0.00 f
10.00 cd
13.33 d
H. bacteriophora (Ar-4 strain)
2000 IJs/ cm2
13.33 c
20.00cd
30.00 bc
1000 IJs/ cm2
10.00 cd
16.67 c
26.67 c
500 IJs/ cm2
3.33 de
13.33 c
13.33 d
Each value is a mean of three replicates with 10 slugs in each replicate.
Tested slugs were observed daily for mortality but only table contains data of 6,10 and 14 days.
The same letter (s) in columns indicates no significant differences at P≤ 0.05according to Duncan's
multiple range test.
Minimum percentage mortalities were obtained when Egyptian H. bacteriophora
strains were used at low concentrations, 500IJs/cm2 and 1000IJs/cm2. Percentage
mortalities in D. leave ranged from 10.0 to 20.0; 13.33 to 23.33; 13.33 to 26.67% by the
application of H. bacteriophora (Serag1 strain), H. bacteriophora (Ht strain) and H.
bacteriophora (Ar-4 strain) after 14 days of exposure, consequently . After 6 days,
percentage mortalities in D. leave ranged from 6.67 to 13.33 % by the application of H.
bacteriophora (Serag1 strain), H. bacteriophora (Ht strain) and H. bacteriophora (Ar-4
strain) , consequently. Whereas, in imported EPNs species, S. carpocapsae (All strain)
and H. bacteriophora (HP88 strain), percentage mortalities values were 56.67 and
26.67%, respectively.
Data in Table (2) showed that exotic nematode species, S. carpocapsae (All strain)
and H. bacteriophora (HP88 strain) were more aggressive killer to D. reticulatum than
native strains of H. bacteriophora. Data revealed that S. carpocapsae (All strain) and
H.bacteriophora (HP88 strain) after 14 days of application, recorded percentage
mortalities in D. reticulatum reached 100 and 66.67 %, respectively.
Evaluation of Certain Egyptian heterorhabditids Isolates….
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Egypt. J. Agronematol., Vol. 18, No.2 (2019)
Moreover, H.bacteriophora (HP88 strain) exhibited lower percentage mortalities, 56.67
and 43.33% at a concentration of 1000 IJs/cm2 and 500 IJs/cm2, respectively. Percentage
mortalities resulted from usage Egyptian isolates were the least at three tested rates 2000,
1000 and 500 IJs/cm2.
Table 2. Molluscicidal activity of Egyptian Heterorhabditis strains against the gray slug
Deroceras reticulatum compared with Steinernema carpocapsae (All strain) and
Heterorhabditis bacteriophora (HP88 strain) after different periods of exposure.
Nematode species
Conc.
Deroceras reticulatum
Mean percent mortality %
6 days
10 days
14 days
S. carpoapsae (All strain)
2000 IJs/ cm2
66.67 a
90.00 a
100.0 a
1000 IJs/cm2
63.33a
80.00 a
90.00 a
500 IJs/cm2
33.33 b
40.00 b
60.00 b
H. bacteriophora (HP88
strain)
2000 IJs/ cm2
50.00 b
56.67 b
66.67 b
1000 IJs/ cm2
33.33 b
43.33 b
56.67 b
500 IJs/ cm2
23.33bc
40.00 b
43.33 c
H. bacteriophora (Serag1
strain)
2000 IJs/ cm2
23.33 c
26.67 c
36.67c
1000 IJs/ cm2
16.67c
26.67bc
26.67d
500 IJs/ cm2
16.67 d
20.00 c
23.33 d
H. bacteriophora (Ht strain)
2000 IJs/ cm2
16.67 c
23.67 c
40.00 c
1000 IJs/ cm2
16.67 d
20.00 c
33.33 cd
500 IJs/ cm2
13.33 d
16.67 c
26.67 d
H. bacteriophora (Ar-4
strain)
2000 IJs/ cm2
20.00 c
30.00 c
46.33 c
1000 IJs/ cm2
16.67 d
23.33 c
33.33 cd
500 IJs/ cm2
13.33 d
20.00 c
26.67 d
Each value is a mean of three replicates with 10 slugs in each replicate.
Tested slugs were observed daily for mortality but only table contains data of 6, 10 and 14days.
The same letter (s) in columns indicates no significant differences at P≤ 0.05according to Duncan's multiple
range test.
Percentage moralities in D.reticulatum were 36.67, 26.67; 40.00, 33.33 and 46.33,
33.33% at a concentration of 2000 IJs/cm2 and 1000 IJs/cm2 with H. bacteriophora
(Serag1 strain), H. bacteriophora (Ht strain) and H. bacteriophora (Ar-4 strain),
respectively. At a concentration of 500 IJs/cm2, percentage mortalities decreased to reach
23.33, 26.67 and 26.67 % after 14 days of application in D.reticulatum , consequently.
Efficacy of two imported nematode species, S. carpocapsae (All strain) and H.
bacteriophora (HP88 strain) compared to Egyptian Heterorhabditis strains as
molluscicidal activity against D. leave and D. reticulatum slugs under laboratory
conditions clearly showed that D. reticulatum was more susceptible than D. laeve and
ineffectiveness of Egyptian strains (Table 3). At highest inoculum level (2000 IJs/ cm2), S.
carpocapsae (All strain) and H. bacteriophora (HP88 strain) induced maximum mean
percentage mortalities with values amounted to 71.11, 94.44 and 44.45, 57.78% in D.
laeve and D.reticulatum , respectively. Egyptian heterorhabditis, H. bacteriophora
(Serag1 strain), H. bacteriophora (Ht strain) and H. bacteriophora (Ar-4 strain), ranked
the next and induced mean percentage mortalities in D. leave amounted to 18.89, 15.67
and 21.11 consequently.
El-Ashry and Abd El-Aal
Egypt. J. Agronematol., Vol. 18, No.2 (2019)
Whereas, in D. reticulatum percentage mortalities were 28.89, 26.78 and 32.11% with
the same mentioned nematode strains. Whereas, tested entomogenous nematodes at
concentrations of 1000 and 500 IJs/cm2 showed lower mean percent mortality against
D.leave and D. reticulatum, nevertheless imported EPNs nematodes were more effective
than Egyptian strains (Table 3).
Table 3. Low susceptibility of two collected slugs, Deroceras laeve and D.reticulatum to
Egyptian Heterorhabditis strains as compared with imported EPNs, S. carpoapsae (All
strain) and H. bacteriophora (HP88 strain).
Nematode species
Concentrations
D. leave
D. reticulatum
% Mortality
mean
% Mortality
Mean
S. carpocapsae (All strain)
2000 IJs/ cm2
71.11
94.44
1000 IJs/cm2
60.00
73.33
500 IJs/cm2
26.67
44.45
H. bacteriophora (HP88 strain)
2000 IJs/ cm2
44.45
57.78
1000 IJs/ cm2
32.22
44.44
500 IJs/ cm2
23.33
35.55
H. bacteriophora (Serag1
strain)
2000 IJs/ cm2
18.89
28.89
1000 IJs/ cm2
16.67
23.34
500 IJs/ cm2
12.22
20.00
H. bacteriophora (Ht strain)
2000 IJs/ cm2
15.67
26.78
1000 IJs/ cm2
14.45
23.33
500 IJs/ cm2
10.00
18.89
H. bacteriophora (Ar-4 strain)
2000 IJs/ cm2
21.11
32.11
1000 IJs/ cm2
16.67
23.33
500 IJs/ cm2
12.22
21.11
The estimation of the results of the molluscicidal activity of Egyptian isolates namely
H.bacteriophora (Serag1 strain), H.bacteriophora (Ht strain) and H. bacteriophora (Ar-4
strain) based on percentage mortalities when compared to S. carpocapsae (All strain) and
H.bacteriophora (HP88 strain) at the three concentrations (2000, 1000 and 500 IJs/cm2)
showed less encourage usage as a specific biological control agent against D.leave and
D.reticulatum.
Terrestrial gastropods species like Deroceras spp. caused damage to important
agricultural and horticultural crops due to feeding or contamination with faeces and
slime (Godan, 1983, 1999 and South, 1992), leading to deterioration in the quality of
the crops and economic loss. D. reticulatum distribute not only in temperate climates
such as Egypt but also in in Europe. Obtained results confirmed those reported by
many authors who detected molluscicidal activity of Steinernema and Heterorhabditis
species infecting slugs and snails (Jaworska, 1993; Wilson and Gaugler, 2000 and
Genena, 2008). Most of these studies were conducted on S.carpocapsae (All Polish
isolates),S.feltiae and H.bacteriphora infected terrestrial slugs, D. agreste and D.
reticulatum (Jaworska, 1993). Likewise , suppressive effects of EPNs have been
demonstrated on other slugs, D. reticulatum or Limax marginatus under laboratory
conditions like H. bacteriophora , H. marelatus , S. carpocapsae , S. glaseri, S.
kushidai, S. longicaudum, S. oregonense, S. riobrave and S. Siamkayai (Kaya, 2001) at
concentration of 1000 IJs/cm2 and 500 IJs/cm2.
Evaluation of Certain Egyptian heterorhabditids Isolates….
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Egypt. J. Agronematol., Vol. 18, No.2 (2019)
EPNs of the Steinernema and Heterorhabditis genera live in the soil and are natural
parasites of insects found in this ecosystem, as well as having a symbiotic relationship with
bacteria of the Xenorhabdus and Photorhabdus genera, respectively (Forst and Clarke ,
2002).Tan and Grewel (2002 & 2003) revealed that P. hermaphrodita associated
symbiotically with the bacterium Moraxella osloensis and kills slugs using an endotoxin
(Bevre & Henrikson). Glen and Coupland (2017) mentioned that slug parasitic nematode ,
P. hermaphrodita was effective as biocontrol agent.
Our results showed that, in most cases imported EPNs (S.carpocapsae All strain and H.
bacteriophora H88 strain) belonging to steinernematids and heterorhabditids were more
effective than local isolates of H. bacteriophora (Serag1 strain, Ht strain and Ar-4 strain)
against terrestrial slugs, D. reticulatum than D. leave even at high or low concentrations
(2000 IJs/cm2, 500 IJs/cm2). D. reticulatum was more susceptible to local isolates than D.
leave.
In conclusion, more efforts should be done to isolate an efficacious nematode species or
to find P. hermaphrodita in Egypt for use against slug pests.
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Heterorhabditis
Deroceras reticulatumD. leave
Deroceras reticulatum D. laeve
.
Phasmarhabditis hermaphrodita
.
S. carpoapsae AllH. bacteriophoraHP88
H. bacteriophoraD.reticulatumD.laeve
S. carpoapsaeD.laeveD. reticulatum
H. bacteriophora HP88
P. hermaphrodita
