







































Agriculture and Food 

Sciences Research 
ISSN(E) : 2411-6653 
ISSN(P) : 2518-0193 
Vol. 3, No. 1, 29-36, 2016 
http://www.asianonlinejournals.com/index.php/AESR 
 

 
 

 

 

 

 

 

29 

 

Pathogenicity of Selected Kenyan Entomopathogenic 

Nematodes of Genus Steinernema against Banana Weevil 

(Cosmopolites Sordidus) 

 
Moses Mwaniki Ndiritu1

     

Dora Kilalo2     

John Wangai Kimenju3     

Shelmith Waruguru Mwaniki4    

1,2,3Department of Plant Science and Crop Protection 
Faculty of Agriculture; University of Nairobi 
4Kenya Agricultural and Livestock Research 
Organization (KALRO-Kabete) 
 
( Corresponding Author) 

 
Abstract 

Banana weevil is a pest with a great impact on banana production in the world. The objective of this study was to 

evaluate the pathogenicity of the Kenyan entomopathogenic nematodes (EPNs) of genus Steinernema against the 

weevil Cosmopolites sordidus (Germar) under laboratory conditions. Adult weevils were trapped from banana 

fields in Maragua, Central Kenya and larvae extracted from the infested banana rhizomes. The adults were treated 

with three Kenyan EPNs Steinernema weiseri, Steinernema yirgalemense and the  new Steinernema spp and with 

Steinernema carpocapsae ALL strain as a standard and plain distilled water as a control in five replicates. The 

treatments were 500ijs, 750ijs and 1000ijs per adult on petri dishes and 1000ijs, 3000ijs and 5000ijs per adult on 

pseudo-stems. The treatments for larvae in petri dishes were 300ijs, 400ijs and 500ijs. The adults were not 

susceptible to all the nematodes at all doses and preparations while larvae were highly susceptible to the four test 

EPNs at all concentrations. There was a significant difference at P<0.05 in the mortality of larvae between 

nematode Steinernema carpocapsae and Steinernema weiseri. A significant difference was observed between 

nematode Steinernema carpocapsae and Steinernema yirgalemense. There was also a significant difference 

between the new Steinernema spp and Steinernema weiseri and finally in the two nematodes the new Steinernema 

spp and Steinernema yirgalemense. All the test nematodes caused over 90 % larval mortality within 48 hours. The 

mean percent mortality of larva increased with nematode concentration for all the test nematodes. The results 

indicated that the four test EPNs significantly (P<0.05) caused high mortality within 24-48 hrs.  The findings 

indicate that the banana weevil larvae are susceptible to the local entomopathogenic nematodes and potentially 

useful in the management of the banana weevil. It is however recommended that more research be conducted on 

the formulation and application technology to enhance their effectiveness in the field. 

 

Keywords: Banana, Cosmopolites sordidus, Management, Entomopathogenic nematodes, Steinernema spp. 

 

Contents 
1. Introduction ............................................................................................................................................................................... 30 

2. Materials and Methods ............................................................................................................................................................. 30 

3. Results ........................................................................................................................................................................................ 31 

4. Discussion ................................................................................................................................................................................... 34 

5. Conclusions and Recommendations ........................................................................................................................................ 35 

References ...................................................................................................................................................................................... 35 

 
 

Citation | Moses Mwaniki Ndiritu; Dora Kilalo; John Wangai Kimenju; Shelmith Waruguru Mwaniki (2016). Pathogenicity of Selected Kenyan 
Entomopathogenic Nematodes of Genus Steinernema against Banana Weevil (Cosmopolites Sordidus). Agriculture and Food Sciences Research, 3(1): 29-

36. 

DOI: 10.20448/journal.512/2016.3.1/512.1.29.36          
ISSN(E) : 2411-6653 

ISSN(P) : 2411-6653 

Licensed:  

Contribution/Acknowledgement: 
This work is licensed under a Creative Commons Attribution 3.0 License  

All authors contributed to the conception and design of the study. We are grateful to the University of Nairobi for 

offering us the opportunity to pursue the study and to the National Council for Science and Technology for supporting 
the research work. We appreciate the assistance of the agriculture extension officer and farmers of Maragua region of 

Murang’a County for their support. 

Funding: This study received no specific financial support. 
Competing Interests: The authors declare that they have no conflict of interests. 

Transparency: The authors confirm that the manuscript is an honest, accurate, and transparent account of the study was reported; that 

no vital features of the study have been omitted; and that any discrepancies from the study as planned have been 
explained. 

History: Received: 11 May 2016/ Revised: 30 May 2016/ Accepted: 6 June 2016/ Published: 10 June 2016 

Ethical: This study follows all ethical practices during writing.   
Publisher: Asian Online Journal Publishing Group 

 

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Agriculture and Food Sciences Research, 2016, 3(1): 29-36 

 

 

 

 

30 

 

1. Introduction 
Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have been 

exploited for several decades as biological tools against many important insect pests in the world [1]; [2]. This has 

been made possible due to major advances in understanding the natural behavior of these nematodes [3]. They have 

also been studied intensively because of their ability to cause natural mortality of soil dwelling arthropods hence 

potential as biocontrol agents [4]. Use of EPN was part of integrated population suppression of pine weevil in the 

United Kingdom [5]. They have been reported to control sweet potato weevils in India and Kenya [6]. In addition, 

use of S.carpocapsae as a biological control against flat-headed root dwelling weevils in roots of apricot trees 

achieved 95% control [7]. 

Many researchers in the world are working on these important biological controls [8]. Of these, research on 

status of commercially available EPNs have been carried out intensively in North American countries and Europe 

while in Asian countries including China, Korea and India the much stressed research work is on the use of EPNs to 

control insect pests and plant pathogens [8]. For most African countries EPN research is still being carried out and in 

some countries non-existent. In developing countries more emphasis and interest is in the mutualistic relationship 

between the EPNs and bacteria hence the need to use them as biological agents for soil pests [8]. The EPNs are also 

commercially available in many parts of the world [9]. Studies on the occurrence of EPNs in Africa have been 

reported. The first record of both families was in a survey done in Nigeria where H. bacteriophora and S. feltiae 

were reported [10]. A number of surveys have been documented showing new species and strains isolated from 

African countries. These have been found to have widespread abundance and are associated with types of habitats in 

South Africa, Kenya, Ethiopia and Egypt [11]; [12]; [13]; [14]; [15]; [16]; [17].  

The EPNs were first reported in Kenya in a survey conducted in the Central highlands and Coastal areas of 

Kenya where a total of 154 nematode isolates among them the new species Steinernema karii was identified [18]; 

[19]. Further surveys in the Rift valley yielded 12 nematode isolates (Mwaniki, pers com.). Currently 33 nematode 

isolates are maintained in three laboratories at Kenya Agricultural and Livestock Research Organization (Mwea, 

Thika and Kabete). The most studied genera are those that are useful in the control of insect pests, the Steirnematidae 

and Heterorhabitidae [20]. They have been identified in Kenya with different species described in Central Highlands, 

Rift Valley and Coastal areas [21]. The banana weevil is the major banana pest in wherever bananas are grown. It 

originated from South East Asia [22] and it is now found in all banana growing regions including the New World, 

Afro tropics, and Oriental and Australasian regions [23]. It came into the African continent from the South East Asia 

through infested planting material and has since established in banana production areas within the continent such as 

Nigeria, Rwanda, Democratic Republic of Congo, Uganda, Tanzania and Kenya [22]. It is a major pest in East Africa 

[24]. Banana weevil is a Coleopteran insect [23]. The adult weevil is nocturnal and very susceptible to desiccation 

and it rarely flies [22]. The newly emerged adult is red brown but turns black two to three days later [23]. It measures 

about 12mm, hard shelled and it has a pronounced snout. The larva is the most destructive stage [22]. They develop 

from the eggs and get into the corms and sometimes in the pseudo-stems making numerous tunnels. The tunneling 

interferes with root initiation and development, nutrient and water uptake there by weakening the plant leading to 

production of a bunch with less weight or eventual death [24]. This study was undertaken to evaluate the 

pathogenicity potential of the Kenyan entomopathogenic nematodes (EPNs) of genus Steinernema against the weevil 

(Cosmopolites sordidus) (Germar) under the laboratory conditions. 

 

2. Materials and Methods 
2.1. Entomopathogenic Nematodes  

Laboratory investigations were carried out in the entomology laboratory of Kenya Agricultural and Livestock 

Research Organization (KALRO) Kabete in Nairobi. Entomopathogenic nematodes were obtained from the 

entomology laboratory. Multiplication of the nematodes was done by the in-vivo method where the insect-bait 

technique with Galleria mellonella larvae described by Poinar [25] and modified by Woodring and Kaya [26]; Parra 

[27]. Four nematode species were tested against the adult weevil and the larval stage of the banana weevil. These 

were the new Steinernema sub spp, Steinernema carpocapsae ALL strain, Steinernema weiseri and Steinernema 

yirgalemense.  Three selected EPNs Steinernema sub spp, Steinernema weiseri and Steinernema yirgalemense had 

been isolated from Kenyan soils. Steinernema carpocapsae ALL strain was used for comparison purposes as it is a 

widely tested species. Infective juveniles were kept in aqueous suspension in plastic containers with perforated lids at 

room temperatures and used in the experiment seven days after harvesting. 

 

2.2. Banana Weevils  
Adult of C. sordidus were trapped using pseudo-stem traps placed in banana orchards in Maragua (0°46′59″ S 

and 37°07′59″ E) in Central Kenya. They were transferred to the laboratory, and maintained in perforated plastic 

buckets with moistened soil and pieces of banana pseudo-stems and corms. They were covered with opaque clothing 

and kept at room temperature. They remained until their use in experiment. Every week, there was exchange of soil 

and both pseudo-stem pieces and corms. In addition, banana corms heavily infested with weevil larvae were obtained 

from banana orchards from Maragua and transferred in plastic bags to the laboratory. Weevil larvae were extracted 

the following day by opening up the corms that were characterized by holes due to infestation. They were carefully 

handled to avoid any injury or mortality before the assay was carried out. The extracted larvae were removed and 

immediately inoculated with nematode treatments. 

 

2.3. Pathogenicity Tests 
Procedures for inoculation and incubation were the same as those used for entomopathogenic nematode 

multiplication with Galleria mellonella larvae [25] modified by Woodring and Kaya [26]; Parra [27]. The only 



Agriculture and Food Sciences Research, 2016, 3(1): 29-36 

 

 

 

 

31 

 

difference was that this time adult and larval stages of the banana weevil were used instead of the normal last instar 

stage of wax moth.   

The design for all the bioassay experiments was completely randomized with five treatments, each treatment had 

five replicates and the experimental unit consisted of six petri dishes 9cm in diameter with 3 banana weevil adults or 

larvae. 

In the first bioassay experiment adult weevils were used as the target insect pests to test the laboratory 

pathogenicity of the selected entomopathogenic nematodes. Four entomopathogenic nematodes were used as 

described above. Five adult weevils were introduced in sterilized petri dishes per nematode species. Filter papers 

were lined on the surface of petri dish to drain the excess water that carried the nematode suspension. Inoculation 

was done by introducing aqueous suspension containing nematodes through sterilized pipette that was specific for 

each nematode treatment. Each nematode treatment was replicated five times. Three different nematode 

concentrations were used and they included: 500 Ijs, 750 Ijs and 1000 Ijs per adult weevil in the petri dish and a 

control that contained plain distilled water only. This first experiment was repeated using the same procedure. After 

the inoculation, each petri dish was sealed with parafilm. The contents were then transferred to a dark chamber at 

room temperature. Observations for mortality were made at 24 hours, 48 hours, 72 hours and 96 hours. The weevils 

were dissected under a light microscope to confirm nematode infection. 

A second bioassay with adult weevils was conducted using the same procedure but this time with a much higher 

dose of entomopathogenic nematodes. The dosage levels were 1000 Ijs, 3000 Ijs and 5000 Ijs per adult weevil and 

plain distilled water was used as a control. Observations were done as before. This bioassay was also done twice. 

A third bioassay with the adult weevil was conducted by using pseudo-stems which were laced with EPNs. Small 

blocks of pseudo-stem of the same size were cut from a fresh banana pseudo-stem. Each nematode treatment was 

applied to the small blocks using a hand pump. This was done all around to maximize the introduction of nematodes.  

Sterilized plastic containers were used in place of petri dishes. They were lined up with filter papers at the bottom so 

as to drain excess water.  The same nematode concentration was applied as in the second weevil bioassay. Only one 

weevil was introduced per treatment with five replications. Plain distilled water was used as the control per 

concentration level.  

The last bioassay involved the use of banana weevil larvae. The procedure was similar to the first bioassay that 

was conducted using the adult weevil. However, the number of larvae introduced per petri dish was three and the 

concentrations were 300, 400 and 500ijs per larval stage. Nematode suspensions were introduced into the petri dishes 

through a sterilized pipette. Plain distilled water was used as a control. Each concentration level was replicated five 

times. The petri dishes were then closed and sealed with parafilm. They were then incubated at room temperature in 

dark chambers. The experiment was done twice. 

Observations for mortality were made every 24 hours up to 96hours. A dead treatment was still with no response 

after brushing. Cadavers infected with the nematodes were pale in color. Cadavers were dissected under a light 

microscope to confirm presence of EPNs. The number of the dead larvae was recorded.  

 

2.4. Statistical Analysis 
The mortality data was subjected to one and two way analysis of variance (ANOVA). Mean separation of the 

treatments that were significantly different at P<0.05 was done using the Turkey-cramers comparison test. The 

analysis was done to compare the pathogenicity of the selected local entomopathogenic nematodes and test their 

effectiveness against banana weevil adult and larval stage.  

 

3. Results 
3.1. Pathogenicity of Different Entomopathogenic Nematodes on the Adult Stage of the Banana 

Weevil under Laboratory Conditions 
Adult weevils were not susceptible to all the four entomopathogenic nematodes at all concentrations in all the 

test arenas and time periods in the three bioassay experiments.  

 

3.2. Comparison of Pathogenicity and Virulence of Selected Entomopathogenic Nematodes against 

the Larvae of Banana Weevil under Laboratory Conditions 
All the test nematodes were pathogenic to the larvae of Cosmopolites sordidus. The dead larvae got a soft 

consistency and a yellow-brown to black colour (pale), a characteristic of larvae killed by the bacteria of the genus 

Xenorhabdus associated with Steinernema species [28]. The mean mortality for each test EPN differed though not 

significant in both the experiments which were carried out under the same conditions. The mean mortality for S. 

yirgalemense spp ranged from (2.00-2.20), new Steinernema spp (2.40-2.55), S.weiseri spp (2.20-2.33) and 

Steinernema carpocapsae spp (2.60-2.73). There was no mortality recorded in the control treatment in both 

experiments (Figures 1 and 2). 

 



Agriculture and Food Sciences Research, 2016, 3(1): 29-36 

 

 

 

 

32 

 

 
(Means with the same letter are not significantly different (P<0.05, Turkey’s multiple range test). S.E.M -standard error of mean) 
Figure-1. Mean mortality of banana weevil larvae following 96hr of exposure to infective juveniles of selected EPNs in the one-on-one assay. 
Source: KALRO- Kabete  

 

There was a significant difference (P<0.05) in mortality of weevil larvae attributed to the three nematode species. 

The mean mortality of banana weevil larvae caused by S.carpocapsae spp was significantly higher (P<0.05) 

compared to S.weiseri spp and S.yirgalemense spp (Figure 1). 

More so, a significant difference at (P<0.05) was observed between nematode new Steinernema spp and 

S.weiseri spp; new Steinernema spp and S.yirgalemense spp (Figure 1). However, no significant difference (P>0.05) 

was observed between nematode S.carpocapsae spp and new Steinernema spp (Figures 1 & 2) S.weiseri spp and 

S.yirgalemense spp (Figures 1) S.carpocapsae spp and S.weiseri spp; new Steinernema spp and S.weiseri spp (Figure 

2). 

 

 
(Means with the same letter are not significantly different (P<0.05, Turkey’s multiple range test). S.E.M -standard error of mean) 

Figure-2. Mean mortality of banana weevil larvae following 96hr of exposure to infective juveniles of selected EPNs the one-on-one assay. 
Source: KALRO- Kabete 

 

S.carpocapsae spp was found to be the most pathogenic and virulent among the tested EPNs in both larval assays 

compared to other test nematodes as shown in Figures 1 and 2 above. 

 

3.3. Comparison of Banana Weevil Larvae Mortality Recorded At Different Time Periods in an 

Assay under Laboratory Conditions 
There were significant differences (P<0.05) between the exposure times of larvae to the test entomopathogenic 

nematodes as shown in Figures 3 and 4 below. 

 

 

(Means with the same letter are not significantly different (P<0.05, Turkey’s multiple range test). S.E.M -standard error of mean) 

Figure-3. Mean mortality of banana weevil larvae recorded after exposure to infective juveniles of selected EPNs for a variable time periods. 
Source: KALRO- Kabete 

 



Agriculture and Food Sciences Research, 2016, 3(1): 29-36 

 

 

 

 

33 

 

 
(Means with the same letter are not significantly different (P<0.05, Turkey’s multiple range test). S.E.M -standard error of mean) 

Figure-4. Mean mortality of banana weevil larvae recorded after exposure to infective juveniles of selected EPNs for a variable time periods. 
Source: KALRO- Kabete 

 

All the nematodes tested caused a high mortality of banana weevil larvae within the first 24 hrs of exposure 

(Figures 3 and 4) but except for S.carpocapsae (Figure 3). The new Steinernema spp caused significantly (P<0.05) 

higher mortality within 24hrs than the rest of the test nematodes.  

It took only 48 hrs for the new Steinernema spp to cause more than 90% larval mortality. S.weiseri spp and 

S.yirgalemense spp took the longest time period to cause more than 90% larval mortality. However, at 48 hrs 

exposure time S.carpocapsae spp achieved a significantly higher (P< 0.05) mean mortality compared to other test 

nematodes (Figures 3 and 4).  

 

3.4. Effect of Ijs Concentrations on the Mortality of Banana Weevil Larvae in a Dose-Response Study 

under Laboratory Conditions 
In this study, the results indicated that the mean mortality of banana weevil larvae increased with increasing 

nematode concentration (300ijs, 400ijs and 500ijs) as shown in Figures 5 and 6 below.  

 

 

(Means with the same letter are not significantly different (P<0.05, Turkey’s multiple range test). S.E.M -standard error of mean) 

Figure-5. Mean mortality of banana weevil larvae following inoculation with different concentrations of infective juveniles of the selected 

EPNs in a dose-response assay. 
Source: KALRO- Kabete 

 

 

(Means with the same letter are not significantly different (P<0.05, Turkey’s multiple range test). S.E.M -standard error of mean) 

Figure-6. Mean mortality of banana weevil larvae following inoculation with different concentrations of infective juveniles of the selected 

EPNs in a dose-response assay. 
Source: KALRO- Kabete 



Agriculture and Food Sciences Research, 2016, 3(1): 29-36 

 

 

 

 

34 

 

 

There was a significant difference (P<0.05) in larvae mortality between nematode concentrations 300ijs and 

500ijs for the two nematodes new Steinernema spp and S. weiseri. However, no significant (P>0.05) differences were 

observed between nematode concentrations 300 ijs and 400 ijs in all the test nematodes. No mortality was observed 

in control treatment. Test nematodes S.yirgalemense spp and new Steinernema spp did not show significant 

difference in all the three nematode concentrations in both bioassays. However, the trend in all the test nematodes 

was evident that after 96 hr of exposure the 500 ijs concentration caused the highest larval mortality (Figures 5 and 

6). 

 

4. Discussion 
In this study, it was evident that all EPNs tested were pathogenic to Cosmopolites sordidus larvae and they 

caused different mortality rates under laboratory conditions. However, none of the test nematodes affected the adult 

stage of the banana weevil.  

Although high concentrations of the test EPNs were used, the adult stage was not susceptible.  This can probably 

be attributed to the heavily sclerotized body and pronounced long snout of the adult weevil [23] making it difficult 

for the Ijs to penetrate inside the weevil. Infective juveniles penetrate the host through the natural openings i.e. 

spiracles, mouth and anus or in some cases directly through the cuticle of certain insects [29]; [30]. According to 

Trevellow and Bedding [31] resistance is almost certainly due to difficulty of nematode entering the adult weevil 

than from establishment once infection is successful. Once inside the insect host, they work symbiotically with 

bacteria carried in their guts. The latter multiply releasing a number of virulence factors. These are toxin complexes, 

hydrolytic enzymes, hemolysins and anti-microbial compounds that cause mortality of insects within 24- 48 hours 

[29]; [31]. A study done by Sirjusignh, et al. [32] demonstrated similar results that local Caribbean EPNs were not 

effective on the adult weevil under laboratory conditions.  

Furthermore, the introduction of fresh pseudo-stem laced with nematode at different dose rates was to maximize 

the contact between the adult weevil and the nematodes in the process of feeding. Adults are attracted to the volatiles 

emanating from the fresh or decomposing pseudo-stems [33]. However, no mortality was recorded. In Tanzania, a 

study carried out by Mwaitulo, et al. [15] reported similar results of resistance of the adult weevil to locally isolated 

EPNs from banana fields in three regions of Morogoro, Mbeya and Pwani.  

All test EPNs caused larval mortality.  These results are consistent with a study conducted in Tanzania by 

Mwaitulo, et al. [15] showed that all local EPN isolates were pathogenic to banana weevil larvae hence causing 

mortality. The test nematodes caused different mortality rates of the weevil larvae. The dead larvae got a soft 

consistency and a yellow to brown to black colour, characteristic of larvae killed by bacteria of the genus 

Xenorhabdus [28]. S. carpocapsae caused higher mean mortality compared to the rest of the test nematodes. This can 

be attributed to the specificity in pathogenicity and virulence of individual EPN isolate. In a study by Koppernhoofer 

and Fuzy [34] noted that differences in the pathogenicity of infective juveniles can be attributed to their foraging 

strategy, the responsiveness of the host immune system, the pathogenicity of the symbiotic bacteria and the number 

of bacterial cells transported by dauers. This explains why in this particular study, the test nematodes caused 

different mortality rates.  

A report by Koppernhoofer and Kaya [35] indicated that Steinernema dauers can carry different amounts of 

bacterial cells in their intestines. For instance, the species S. scapterisci contains a small amount of bacterial cells 

compared to S.carpocapsae that has a large number of bacterial cells, causing higher pathogenicity but at the expense 

of lower survival in the environment [36]. All tested nematodes caused more than 90% mortality of the larvae. In a 

study conducted in Canary Island, a 100% mortality banana weevil larva was reported using indigenous EPN 

(Heterorhabditis and Steinernema species). Previous authors have reported susceptibility to EPNs among larvae of 

other beetles such as Diaprepes abbreviatus (Coleoptera: curculionidae) [37] Capnodis tenebrionis [38] and 

Premnotrypes sutulicallus [39]. The mortality of banana weevil larvae in this study could be attributed to the 

physical appearance (soft and fleshy cuticle, abdominal segments) that enabled EPNs to penetrate easily alongside 

the mouth and anus. Previous histopathological studies have shown that Ijs enters the larvae through the cuticle and 

less often through the anus and mouth [40]. 

From the results in this study all the test nematodes caused a significant high mean mortality rate of larvae within 

the first 24-48 hours of exposure. This demonstrates the high virulence and infectivity potential of the local EPNs 

tested against the banana weevil larval. The mortality was confirmed to be due to EPN infection through dissection 

of the cadavers to check for the presence of Ijs in the haemocoel. Entomopathogenic nematodes kill the host by 

inducing septicaemia within 24-48 hours of infection [41]. 

A dose-response assay showed no significant difference in larval mortality between 300ijs and 400ijs 

concentrations. 500 ijs concentration for all the test nematodes caused larval mortality and was different to 300ijs. 

This can probably be attributed to the numbers. It is said there is strength in numbers and hence the higher 

concentration of ijs showed high virulence and pathogenicity differences in the EPN species, humoral and immune 

response of the host [41].  

Although there was no consistency across all the three Ijs concentrations, there was a positive relationship that 

weevil larval mortality increased with increasing concentrations. Larval mortality observed for S.carpocapsae and S. 

yirgalemense did not differ in the mortality rates caused to the larvae based on concentration.  

The rest of the tested nematodes did not differ in causing mortality at the two concentration levels of 300ijs and 

500ijs. This indicates the importance of dosage rates.  The results partially concur with a study conducted by 

Mwaitulo, et al. [15] who reported that the banana weevil mortality increased significantly with increasing native 

nematode dosage. However, these same results differ with a study conducted by Padilla-Cubas, et al. [42] that 

showed an increase in Ijs dosage does not necessarily cause an increase of banana larvae mortality. A dose- mortality 

response was observed by Schmitt [43]. Previous studies have reported significant differences based on EPN 



Agriculture and Food Sciences Research, 2016, 3(1): 29-36 

 

 

 

 

35 

 

concentration and larvae stage mortality in other insect pest orders. A study conducted in Turkey showed that native 

EPN Ijs concentration (0,100, 500 and 1000ijs) had differences in causing mortality of P. operculella larvae [44]. 

 

5. Conclusions and Recommendations 
The tested Kenyan EPNs were able to parasitize Cosmopolites sordidus larvae but not the adult under laboratory 

conditions. All the nematodes tested caused above 90% banana weevil larval mortality. Nematode species and the 

nematode concentration levels showed differences in efficiency against the weevil larvae. In addition all tested 

nematodes caused high mortality within 24-48 hrs of exposure indicating a high susceptibility of banana weevil 

larvae to the tested nematodes. These tested nematodes have potential for field management of the banana weevil 

since EPNs are known to search and locate susceptible hosts in cryptic habitats like within the banana pseudo-stem 

and corms. Larvae are found within the small holes on the surface of the rhizome, which are in contact with exterior. 

They are also found living in long galleries inside the rhizomes which are ideal conditions for EPNs survival and 

infection of hosts. The larval stage is the most destructive stage of banana weevil and if targeted for control through 

EPN application would lead to a reduction of banana weevil damage hence higher banana yields. The most effective 

EPN was S.carpocapsae and can be used at 500 ijs concentration level in the laboratory to kill the weevil larvae 

Future work is necessary to test more native nematodes for efficacy, appropriate formulations and application 

techniques in banana fields to enable the adoption EPNs against the banana weevil larvae in the field. In addition, 

further research in EPN storage is needed for longer nematode life span. Better storage and application technology of 

EPNs will enhance the adoption of EPNs for the management of banana weevil larvae and in the integration of 

entomopathogenic nematodes in pest management programs. 

 

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