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Full Research Article

Insecticidal Effect of the Essential Oil of Eucalyptus globulus Leaves on the Aphid, Aphis craccivora (Homoptera: Aphididae) of Vigna unguiculata in Central Region of Togo

E
Essolakina Magnim Bokobana1,*
https://orcid.org/0009-0009-9484-5349
S
Sissadèma Tagba1
N
Nafadjara Abouwaliou Nadio1
K
Koffi Koba2
K
Komla Sanda2
1Department of Sustainable Plant Protection, High Institute of Agricultural Professions, University of Kara, Togo.
2Département de Phytotechnie, Ecole Supérieure d’Agronomie, Université de Lomé, Lomé, Togo.

ABSTRACT

Background: Vigna unguiculata (L.) Walp. is an important vital crop in the diet of populations, whose productivity is declining due to the pressure of pests, including Aphis cracivora Koch (Homoptera: Aphididae). To combat these pests, farmers use synthetic chemical products, which are highly toxic to human health and useful entomofauna. To remedy these problems and find alternative to these synthetic chemical pesticides, this study aims to evaluate the efficacy of a formulation based on the essential oil of E. globulus on A. craccivora.

Methods: The test was realised in the field using the Fischer experimental design with five replicates. Each replicate consisted of three treatments with the E. globulus essential oil formulation at different concentrations (0.1, 0.5 and 1%), a positive control (treatment with the synthetic insecticide K-optimal (Acetamiprid-Lamdacyhalothrin)) and an untreated plot. A. craccivora population dynamics and pod yield were the parameters evaluated during the experimentation.

Result: The essential oil of E. globulus formulation, at a concentration of 1% reduced considerably the density of A. craccivora population (4.8±0.12 aphids per plant) and induce a higher yield in terms of number of pods (12.42±1.16 pods per plant) compared to the untreated plot (48.2±1.02 aphids per plant; 6.325±0.33 pods per plant). Statistical analysis showed that the effect of the formulation based on 1% of E. globulus essential oil was similar to the synthetic insecticide effect.

INTRODUCTION

Vigna unguiculata (L.) is a widely grown legume with major production in West Africa (Kim et al., 2025). Countries such as Nigeria, Niger, Burkina-Faso and Ghana are the major producers which has an average yield of 0.87 t/ha (FAO, 2025). The seeds of Vigna unguiculata contain a high protein content (19-35%), very rich in lysine and tryptophan, two essential amino acids (Ibro et al., 2014). It helps reduce malnutrition and also contributes to increase the income of smallholders (Gomes et al., 2019; Manda et al., 2020; Vaishna et al., 2025).
       
Despite its importance in Togolese farming systems, Vigna unguiculata yields remain low, fluctuating between 0.2 and 0.45 t/ha (DSID, 2017). This, due to high pressure of pest, including aphids which negatively affect yields and the nutritional quality of the seeds; aphids feed by sucking the sap from the plant, which causes the slowdown of plant growth, the curling and premature fall of leaves, a reduction in the number of pods and seeds and a reduction in seed size (Akello and Sikora, 2012). They also transmit certain phytoviruses.
       
Most farmers use synthetic chemical pesticides to control these pests. Studies have shown that these products are highly toxic to humans and the environment. They are persistent in the environment and destroy useful entomofauna. Other studies have shown that aphids develop resistance to these synthetic chemical insecticides (Bonnemain and Chollet, 2003; Harris, 2003). In this situation, it is important to adopt a biological control approach. Several studies have demonstrated the insecticidal efficacy of plant extracts (Adesina and Enudeme, 2018; Akantetou et al., 2021; Mario et al., 2021; Labdelli et al., 2022; Nadio et al., 2023). These extracts, especially essential oils contain a cocktail of biomolecules, which are less persistent in the environment, less toxic and can solve the problem of resistance. In the context of these findings, we hypothesised that phytosanitary treatment of Vigna unguiculata crop with a formulation based on the essential oil of Eucalyptus globulus would lead to a reduction of the population of A. craccivora aphids and promote good production. E. globulus is an indigenous plant from Togo that has for a long time been considered as a medicinal plant, whose extracts are used for the treatment of respiratory tract infections (Gbekley et al., 2017; Sharma et al., 2021; Ghedira, 2025). Knowledge of its chemical composition has led researchers to explore its effectiveness on crop pests. In Togo, the effectiveness of its essential oil has been tested on several insect pests, namely the cotton pests Pectinophora gossypiella S. and Thaumatotibia leucotreta M. (Lepidoptera) (Nadio et al., 2023) and on post-harvest pests of corn Sitophilus zeamais Motsch and Tribolium castaneum Herbst. (bokobana et al., 2022). However, its effectiveness has never been tested on aphids A. craccivora in cowpea crops in Togo.The aim of our work is, therefore, to evaluate the aphicidal efficacy of the essential oil of E. globulus Labill. leaves on the aphid A. craccivora Koch (Homoptera: Aphididae).

MATERIALS AND METHODS

Experimental site
 
The experimentation was set up at the agro-ecological station of Tchébébé in central region of Togo. Its geographical coordinates are: N: 8.42325° and E: 0.98107°. This site has a semi-humid tropical climate of the Sudanian type with a monomodal rainfall pattern characterised by two seasons: a rainy season from April to October and a dry season from November to March. Annual rainfall in the year of the experimentation (2023) is approximately 1390.2 mm.
 
Experimental design
 
The experimentation was conducted on V. unguiculata, Vitoco variety. The experimental design was the randomized complete block design with five replicates. Each replicate consisted of five objects corresponding to the different treatments. Each treatment covered four ridges and was separated from one other by two other ridges that were used as a barrier to prevent insecticides passing from one treatment to another during spraying. Each ridge was 5 m long. The following treatments were carried out:
- Control (no pesticide treatment (T0).
- Treatment with E. globulus essential oil at a concentration of 0.1% (T1).
- Treatment with E. globulus essential oil at a concentration of 0.5% (T2).
- Treatment with essential oil of E. globulus at a concentration of 1% (T3).
- Treatment with the synthetic chemical insecticide K-optimal (Acetamiprid-Lamdacyhalothrin) at a dose of 1 L/ha (T4);
       
The sowing scheme adopted was 40 cm between seed hole and 50 cm between ridges. The sowing rate adopted was 2 seeds per hole. Biopesticide treatments were carried out once a week from the 15th day after emergence. These treatments were stopped one week before harvesting.
       
The synthetic chemical insecticide was applied twice according to what is recommended by the agriculture technical services: the first application was done 15 days after emergence and the second when the flower buds appeared. It was bought in a SPROCA store in Togo.
       
Two liters of each formulation were applied on 7.5 m2 area for every treatment.
 
Biopesticide formulation
 
Formulations were carried out by mixing E. globulus essential oil with a solution of potassium palmitate in proportions of 75% and 25% (v/v), respectively. The essential oil of E. globulus used is obtained from the leaves; it contains p-Cymene (23.38%), D-Limonene (12.16%), l,8-cineole (24.47%) and ã- Terpinene (29.91%) as the major compounds (Bokobana et al., 2022). The 5% concentration of potassium palmitate solution was used as an emulsifier to facilitate dilution with water and ensure stable emulsions.Table 1 illustrates the composition of 2 liters of biopesticide solution sprayed on an elementary plot measuring 7.5 m2.

Table 1: Composition of 2 L of biopesticides solution sprayed.


 
Observation and data collection
 
Aphids were identified using the identification keys of Blackman and Eastop (2000). Data collection consisted of:                                                                                          
- Weekly counts (once a week) of larvae and adults of A. craccivora on ten (10) randomly selected plants of each treatment, which were marked. On each plant selected and marked, aphids were counted on the five (5) subterminal leaves (Denéchère, 1981) and before the phytosanitary treatments. When larvae were present on the leaves, a 4.9 cm2 magnifying glass was used for observation. Data collection began on the 15th day after emergence of plant. 
- Counting the number of pods on ten plants selected previously per treatment at the harvest period.
 
Statistical analysis
 
The results obtained were analysed using XLSTAT version 2021.2 software. The results were analyzed using the analysis of variance (ANOVA) procedure and the treatment means were compared by Duncan test at the 0.05 probability level. The curves and histograms were drawn using Excel.

RESULTS AND DISCUSSION

Effect of treatments on dynamic of A. craccivora population
 
Firstly, the period from 15 to 22 days after emergence is characterised initially by an increase of aphid numbers in each plot, with a higher level in the control plot (79.2 aphids per plant). From 22 to 56 days after emergence, we noted generally a decrease in aphid numbers in all treatments, despite the up-and-down variations of average number of these aphids before 56 days after emergence (Fig 1).

Fig 1: A. craccivora population dynamics depending on different treatments.


       
The average numbers of A. craccivora per plant during the experimentation are shown by Fig 2.

​

Fig 2: Average number of aphids per plant depending on different treatments.


       
Discrimination of the means using Duncan’s test at the 5% threshold shows 3 homogeneous groups, revealing a significant difference between the results obtained. The analysis shows that the average numbers of aphids per plant obtained in treatments T3 and T4 are statistically identical to each other, but statistically different from the average numbers of aphids obtained in the other treatments.
       
The formulation became increasingly effective in reducing the A. craccivora population density as the essential oil concentration increased. A high concentration of E. globulus essential oil implies the presence of an important quantity of active molecules to which the target insects are sensitive, thus increasing the efficacy of the bioinsecticide; these biomolecules, mostly monoterpenes such as p-Cymene, D-Limonene, l,8-cineole and γ-Terpinene (Bokobana et al., 2022) have a neurotoxic effect; they interfere with the neuromodulator octopamine and GABA chloride channels (Priestley et al., 2003; Jankowska et al., 2018). The effect of treatments on these pests would depend on the nature of the insecticide and its active ingredient concentration. In the case of our study, the synthetic chemical insecticide (K-optimal (Acetamiprid-Lamdacyhalothrin) and the bioinsecticide at a concentration of 1% (T3) reduced significantly the population density of A. craccivora compared to the control. In general, bioinsecticides based on the essential oil of plant are less persistent than synthetic chemical insecticides due to the highly volatile nature of the active ingredients they contain (Isman, 2008; Mehinto et al., 2015). The reduction of the population density of A. craccivora by this formulation would be effected by an insect repellent and insecticidal action of the different substances tested.
 
Effect of different treatments on pod yields
 
Discrimination of means using Duncan’s test at the 5% threshold reveals two homogeneous groups. Analysis of these homogeneous groups shows that there are no significant differences between the average number of pods obtained in treatments T0 and T1; nor between the average number of pods obtained in treatments T2, T3 and T4, which represent the highest numbers (Table 2).

Table 2: Average number of pod per plant.


       
An increase of cowpea pod production compared with the control was obtained in relation to the essential oil concentration increase. The highest mean number of pods was obtained in plots treated with the synthetic chemical insecticide and the biopesticide formulation at concentrations of 0.5% and 1%. The average number of pods obtained in plots treated with the synthetic chemical insecticide (14.4±0.8) was statistically identical to the numbers obtained in plots treated with the 0.5% and 1% concentration formulations (12.4±1.4 and 12.425±1.16, respectively). According to Vaissayre and Cauquil (2000), a low density of biting-sucking insects on plant reduces the quantity of sap ingested and the transmission of viruses. Insecticide treatments, by reducing the aphid population density on plant, therefore ensure good growth and pod productivity.
       
Pesticide formulations based on essential plant oils are potential alternatives to synthetic chemical pesticides. This study reports for the first time the efficacy of a pesticidal formulation based on the essential oil of E. globulus in the protection of cowpea crops against A. craccivora. E. globulus essential oil has most often been used in the formulation of pharmaceutical products in the medical field (Singh et al., 2021; Majeed et al., 2024); but nowadays there are also formulations based on E. globulus extracts used in plant protection. This is the case of a natural formulation used to combat potato mildew (Picaud, 2019).
       
There are biopesticides based on plant extracts which are also effective against Aphis craccivora aphids on cowpeas. This concerns two Wettable Powder formulation based on Polygonum hydropiper flowers and Nicotiana tabacum leaves; these formulations have shown more than 65% effectiveness against these aphids (Gosh, 2024).
       
Studies have revealed the pesticidal properties of formulations based on other botanical extracts from tropical flora against crop pests (Bambara and Tiemtoré, 2008; Ramadass  and Thiagarajan, 2021; Semako et al., 2021; Sane, 2021); among the plant species used for formulation, the use of Azadirachta indica organs appears to be one of the most popular (Adhikari et al., 2020).
       
It’s important to note that the use of plant extracts over large areas can lead to massive destruction of the plants, so it’s important to plan for their replacement or replanting.

CONCLUSION

The aim of this study was to reduce the use of synthetic chemical pesticides by promoting the use of biopesticides in the management of the main pests of cowpea (V. unguiculata), such as A. craccivora. The results obtained showed that the toxicity of the essential oil is depending on concentration. Treatment with the synthetic chemical insecticide showed comparable effects with the high concentration of bioinsecticide. The high concentration formulation of E. globulus essential oil reduced considerably aphid population density per plant compared to the control and improved pod production. E. globulus essential oil can therefore be used as an active raw material in the formulation of biopesticides. One problem still to be resolved with bioinsecticides based on essential oil is their high volatility. It would therefore be necessary to develop strategies to resolve these problems for more sustained protection of the environment while ensuring high crop productivity.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

CONFLICTS OF INTEREST

All authors declare that they have no conflict of interest.

REFERENCES


  1. Adesina, J.M. and Enudeme, D.C. (2018). Insecticidal Efficacy of Some Plant Aqueous Extracts Mixtures against Post Flowering Insect Pest of Cowpea. 36th Annual Conference of Horticultural Society of Nigeria. Nasarawa State, Nigeria: Horticultural Society of Nigeria.

  2. Adhikari, K., Sudip, B., Dikshya, N., Jiban, S. (2020). Use of neem (Azadirachta indica A. Juss) as a biopesticide in agriculture: A review. Journal of Agriculture and applied biology. 1(2): 100-117. doi: https://doi.org/10.11594/jaab.01.02. 08.

  3. Akantetou, P.K., Tozoou, P., Bokobana, M.E., Nadio, N.A., Kilimou, P., Koba, K., Poutouli, W., Sanda, K. (2021). Effets de la fumure minérale et des prédateurs sur le niveau d’infestation du cotonnier par le puceron (Homoptera: Aphididae) au Togo. African Crop Science Journal. 29(1): 13-30. https:// doi.org/10.4314/acsj.v29i1.2.

  4. Akello, J. and Sikora, R. (2012). Systemic acropedal influence of endophyte seed treatment on Acyrthosiphon pisum and Aphis fabae offspring development and reproductive fitness. Biological control. 61(3): 215-221. https://doi. org/10.1016/j.biocontrol.2012.02.007.

  5. Bambara, D. and Tiemtoré, J. (2008). Efficacité biopesticide de Hyptis spicigera Lam., Azadirachta indica A. Juss. et Euphorbia balsamifera Ait. sur le niébé Vigna unguculata L. Walp. Tropicultura. 26(1): 53-55.

  6. Blackman, R.L. and Eastop, V.F. (2000). Aphid on the World’s Crops: An Identification Information Guide, 2nd Edition. John Wiley and Sons, Chichester.

  7. Bokobana, E.M., Nadio, N.A., Eloh, K., Akantetou, P., Tozoou, P., Koba, K., Sanda, K. (2022). Insecticidal activity of the essential oil of Eucalyptus globulus Labill. (Myrtaceae) on Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) and Tribolium castaneum Herbst, corn pests in storage. International Journal of Green and Herbal Chemistry. 11(2): 193-200. doi: 10.24214/ijghc/gc/11/2/19300.

  8. Bonnemain, J.L. and Chollet, J.F. (2003). L’arsenal phytosanitaire face aux ennemis des plantes. Considérations générales. Comptes Rendus Biologies. 326(1): 1-7. doi: 10.1016/ S1631-0691(03)00014-3.

  9. Denéchère, M. (1981). Note sur la distribution et l’évaluation des populations d’Aphis gossypii Glov. Coton Fibres tropicales. 36(3): 271-180.

  10. DSID. (2017). Caractéristiques structurales de l’agriculture togolaise. Rapport principal. Direction des Statistiques Agricoles, de l’Informatique et de la Documentation, Lomé. p.72.

  11. FAO. (2025). Food and Agriculture Organization Statistical Database. Retrieved from https://www.fao.org/faostat/en/?and data.)#data/QCL.

  12. Gbekley, H.E., Katawa, G., Karou, S.D., Anani, S., Tchadjobo, T., Ameyapoh, Y., Batawila, K., Simpore, J. (2017). Ethnobotanical study of plants used to treat asthma in the maritime region in Togo. Afr. J. Tradit. Complement Altern. Med. 14(1): 196-212. doi: 10.21010/ajtcam.v14i1.22.

  13. Ghedira, K. (2025). Eucalyptus globulus Labill. (Myrtaceae). Phytothérapie. 23(1): 25-31. doi: 10.3166/phyto2025-0442.

  14. Ghosh, S.K. (2024). Bio-efficacy of plants based formulations for the management of cowpea aphid (Aphis craccivora Koch.). Legume Research. 47(2): 284-290. doi: 10.18805/LR-4636.

  15. Gomes, A.M.F., Nhantumbo, N., Ferreira-Pinto, M., Massinga, R., Ramalho, J.C. and Ribeiro-Barros, A. (2019). Breeding elite cowpea [Vigna unguiculata (L.) Walp] varieties for improved food security and income in Africa: Opportunities and challenges, in Legume Crops-Characterization and Breeding for Improved Food Security. London, United Kingdom: IntechOpen, 62-640. doi: 10.5772/intechopen. 84985.

  16. Harris, R. (2003). Synergism in the essential oil world. International Journal of Aromatherapy. 12: 179-186. https://doi.org/ 10.1016/S0962-4562(02)00083-8.

  17. Ibro, G., Sorgho, M.C., Idris, A.A., Moussa, B., Baributsa, D., Lowenberg- DeBoer, J. (2014). Adoption of cowpea hermetic storage by women in Nigeria, Niger and Burkina Faso. Journal of stored products research. 58: 87-96. https://doi.org/ 10.1016/j.jspr.2014.02.007

  18. Isman, M.B. (2008). Problèmes et perspectives de commercialisation des insecticides d’origine botanique, pp. 465-476. In: C. Regnault-Roger, J.R. Bernard et C. Vincent (Eds), Biopesticides d’origine végétale - 2ème edition. Tec and doc, Paris, France.

  19. Jankowska, M., Wyszkowska, J., Stankiewicz, M., Rogalska, J. (2018). Molecular targets for components of essential oils in the insect nervous system-A Review. Molecules. 23(1): 34-53. https://doi.org/10.3390/molecules23010 034.

  20. Kim, D.K., Ochar, K., Iwar, K., Ha, B.K., Kim, S.H. (2025). Cowpea (Vigna unguiculata L.) production, genetic resources and strategic breeding priorities for sustainable food security: A review. Front. Plant Sci. 16: 1562142. doi: 10.3389/fpls.2025.1562142.

  21. Labdelli, F., Bousmaha, F., Mazrou, K., Moulay, M., Adamou-Djerbaoui, M., Rabahi, H. (2022). Insecticidal effect of eucalyptus essential oils on mortalities of storage pests of grains Sitophilus oryzae and Sitophilus granarius in the region of Tissemsilet Algeria. Indian Journal of Agricultural Research. 56(6): 755-758. doi: 10.18805/IJARe.A-661.

  22. Majeed, H., Iftikhar, T., Nadeem, M., Nazir, M. (2024). Green synthesis of Eucalyptus globulus zinc nanoparticles and its use in antimicrobial insect repellent paint formulation in bulk industrial production. Heliyon, 10: e24467. https://doi.org/ 10.1016/j.heliyon.2024.e24467.

  23. Manda, J., Alene, A.D., Tufa, A.H., Feleke, S., Abdoulaye, T., Omoigui, L.O. (2020). Market participation, household food security and income: The case of cowpea producers in northern Nigeria. Food Energy Secur. 9: e211. doi: 10.1002/fes3.211.

  24. Mario, M.B., Astuti, L.P., Hsu, J.L. and Kafle, L. (2021). Fumigant activity of four plant powders against cowpea weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae) in Stored Adzuki Bean. Legume Research. 44(6): 667-672. doi: 10.18805/LR-533.

  25. Mehinto, J.T., Atachi, P., Elégbédé, M., Kpindou, O.K.D., Tamo, M. (2015). Efficacité comparée des insecticides de natures différentes dans la gestion des insectes ravageurs du niébé au Centre du Bénin. Journal Applied Bioscience. 84: 7695-7706. https://doi.org/10.4314/jab.v84i1.1.

  26. Nadio, N.A., Gmasson, G., Bokobana, E.M., Akantetou, P.A., Poutaouli, W., Koba, K., Sanda, K. (2023). Effet Larvicide de l’Huile Essentielle d’Eucalyptus globulus Labill. (Myrtaceae) sur Pectinophora gossypiella S. et Thaumatotibia leucotreta M. (Lepidoptera), Ravageurs Carpophages du Cotonnier au Togo. European Scientific Journal. 19(30): 181-199. https://doi.org/10.19044/esj.2023.v19n30p181.

  27. Picaud, T. (2019). Formulation naturelle innovante à base d’extrait d’Eucalyptus globulus permettant de gérer le mildiou de la pomme de terre. Brevet d’invention belge BE1025821B1.

  28. Priestley, C., Williamson, E., Wafford, K., Sattelle, D. (2003). Thymol, a constituent of thyme essential oil, is a positive allosteric modulator of human GABA (A) receptors and a homo- oligomeric GABA receptor from Drosophila melanogaster. British Journal of Pharmacology. 140(8): 1363-1372. https://doi.org/10.1038/sj.bjp.0705542.

  29. Ramadass, M. and Thiagarajan, P. (2021). Current Trends and Emerging Technologies for Pest Control Management of Rice (Oryza sativa) Plants, pp. 125-179. In: K.M. Gothandam, R. Srinivasan, S. Ranjan, N. Dasgupta, E. Lichtfouse (eds), Environmental Biotechnology, Volume 4, Environmental Chemistry for a Sustainable World, 68. Springer, Cham., New York, USA. 

  30. Sane, B. (2021). Efficacité biologique des extraits d’Azadirachta indica A. Juss, Hyptis suaveolens (L.) Poit et Anacardium occidentale Linn. dans la lutte contre Helicoverpa armigera (Hübner, 1808) (Lepidoptera, Noctuidae) ravageur du cotonnier (Gossypium hirsutum L.) au Sénégal. Thèse de doctorat, Université Cheikh Anta Diop, Dakar.

  31. Semako, A.G., Aboudou, K., Chatigre, K.O., Noukpozounkou, M.S.P., Soumanou, M.M. (2021). Optimisation in vitro de l’efficacité des biopesticides dans la lutte contre les principaux ravageurs du niébé par la méthode des surfaces de réponse. International Journal of Biological and Chemical Sciences. 15(1): 41-53. https://dx.doi.org/10.4314/ijbcs. v15i1.5.

  32. Sharma, S., Sushma. and Nishtha. (2021). A Review on Eucalyptus Globulus-An Authentic Herb. Journal of Pharmaceutical Research International. 33(53B): 107–114. doi: 10.9734/ jpri/2021/v33i53B33686.

  33. Singh, G., Khan, M.W., Ahirwar, C.S., Gupta, V. and Soni, K. (2021). Formulation and Biological Implication of Eucalyptus globulus and Trachspermum ammi Organogel for Topical Delivery. International Journal of Current Research. 13(12): 19790-19793. https://doi.org/10.24941/ijcr.426 06.12.2021.

  34. Vaishna, T., Radhakrishnan, V.V. and Resmi, L. (2025). Genetic diversity of cowpea: implications for crop Improvement and food security: A Review. Agricultural Reviews. 1-8. doi: 10.18805/ag.R-2866.

  35. Vaissayre, M. and Cauquil, J. (2000). Principaux ravageurs et maladies du cotonnier en Afrique au sud du Sahara. CIRAD, Montpellier, France.
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    Full Research Article

    Insecticidal Effect of the Essential Oil of Eucalyptus globulus Leaves on the Aphid, Aphis craccivora (Homoptera: Aphididae) of Vigna unguiculata in Central Region of Togo

    E
    Essolakina Magnim Bokobana1,*
    https://orcid.org/0009-0009-9484-5349
    S
    Sissadèma Tagba1
    N
    Nafadjara Abouwaliou Nadio1
    K
    Koffi Koba2
    K
    Komla Sanda2
    1Department of Sustainable Plant Protection, High Institute of Agricultural Professions, University of Kara, Togo.
    2Département de Phytotechnie, Ecole Supérieure d’Agronomie, Université de Lomé, Lomé, Togo.

    ABSTRACT

    Background: Vigna unguiculata (L.) Walp. is an important vital crop in the diet of populations, whose productivity is declining due to the pressure of pests, including Aphis cracivora Koch (Homoptera: Aphididae). To combat these pests, farmers use synthetic chemical products, which are highly toxic to human health and useful entomofauna. To remedy these problems and find alternative to these synthetic chemical pesticides, this study aims to evaluate the efficacy of a formulation based on the essential oil of E. globulus on A. craccivora.

    Methods: The test was realised in the field using the Fischer experimental design with five replicates. Each replicate consisted of three treatments with the E. globulus essential oil formulation at different concentrations (0.1, 0.5 and 1%), a positive control (treatment with the synthetic insecticide K-optimal (Acetamiprid-Lamdacyhalothrin)) and an untreated plot. A. craccivora population dynamics and pod yield were the parameters evaluated during the experimentation.

    Result: The essential oil of E. globulus formulation, at a concentration of 1% reduced considerably the density of A. craccivora population (4.8±0.12 aphids per plant) and induce a higher yield in terms of number of pods (12.42±1.16 pods per plant) compared to the untreated plot (48.2±1.02 aphids per plant; 6.325±0.33 pods per plant). Statistical analysis showed that the effect of the formulation based on 1% of E. globulus essential oil was similar to the synthetic insecticide effect.

    INTRODUCTION

    Vigna unguiculata (L.) is a widely grown legume with major production in West Africa (Kim et al., 2025). Countries such as Nigeria, Niger, Burkina-Faso and Ghana are the major producers which has an average yield of 0.87 t/ha (FAO, 2025). The seeds of Vigna unguiculata contain a high protein content (19-35%), very rich in lysine and tryptophan, two essential amino acids (Ibro et al., 2014). It helps reduce malnutrition and also contributes to increase the income of smallholders (Gomes et al., 2019; Manda et al., 2020; Vaishna et al., 2025).
           
    Despite its importance in Togolese farming systems, Vigna unguiculata yields remain low, fluctuating between 0.2 and 0.45 t/ha (DSID, 2017). This, due to high pressure of pest, including aphids which negatively affect yields and the nutritional quality of the seeds; aphids feed by sucking the sap from the plant, which causes the slowdown of plant growth, the curling and premature fall of leaves, a reduction in the number of pods and seeds and a reduction in seed size (Akello and Sikora, 2012). They also transmit certain phytoviruses.
           
    Most farmers use synthetic chemical pesticides to control these pests. Studies have shown that these products are highly toxic to humans and the environment. They are persistent in the environment and destroy useful entomofauna. Other studies have shown that aphids develop resistance to these synthetic chemical insecticides (Bonnemain and Chollet, 2003; Harris, 2003). In this situation, it is important to adopt a biological control approach. Several studies have demonstrated the insecticidal efficacy of plant extracts (Adesina and Enudeme, 2018; Akantetou et al., 2021; Mario et al., 2021; Labdelli et al., 2022; Nadio et al., 2023). These extracts, especially essential oils contain a cocktail of biomolecules, which are less persistent in the environment, less toxic and can solve the problem of resistance. In the context of these findings, we hypothesised that phytosanitary treatment of Vigna unguiculata crop with a formulation based on the essential oil of Eucalyptus globulus would lead to a reduction of the population of A. craccivora aphids and promote good production. E. globulus is an indigenous plant from Togo that has for a long time been considered as a medicinal plant, whose extracts are used for the treatment of respiratory tract infections (Gbekley et al., 2017; Sharma et al., 2021; Ghedira, 2025). Knowledge of its chemical composition has led researchers to explore its effectiveness on crop pests. In Togo, the effectiveness of its essential oil has been tested on several insect pests, namely the cotton pests Pectinophora gossypiella S. and Thaumatotibia leucotreta M. (Lepidoptera) (Nadio et al., 2023) and on post-harvest pests of corn Sitophilus zeamais Motsch and Tribolium castaneum Herbst. (bokobana et al., 2022). However, its effectiveness has never been tested on aphids A. craccivora in cowpea crops in Togo.The aim of our work is, therefore, to evaluate the aphicidal efficacy of the essential oil of E. globulus Labill. leaves on the aphid A. craccivora Koch (Homoptera: Aphididae).

    MATERIALS AND METHODS

    Experimental site
     
    The experimentation was set up at the agro-ecological station of Tchébébé in central region of Togo. Its geographical coordinates are: N: 8.42325° and E: 0.98107°. This site has a semi-humid tropical climate of the Sudanian type with a monomodal rainfall pattern characterised by two seasons: a rainy season from April to October and a dry season from November to March. Annual rainfall in the year of the experimentation (2023) is approximately 1390.2 mm.
     
    Experimental design
     
    The experimentation was conducted on V. unguiculata, Vitoco variety. The experimental design was the randomized complete block design with five replicates. Each replicate consisted of five objects corresponding to the different treatments. Each treatment covered four ridges and was separated from one other by two other ridges that were used as a barrier to prevent insecticides passing from one treatment to another during spraying. Each ridge was 5 m long. The following treatments were carried out:
    - Control (no pesticide treatment (T0).
    - Treatment with E. globulus essential oil at a concentration of 0.1% (T1).
    - Treatment with E. globulus essential oil at a concentration of 0.5% (T2).
    - Treatment with essential oil of E. globulus at a concentration of 1% (T3).
    - Treatment with the synthetic chemical insecticide K-optimal (Acetamiprid-Lamdacyhalothrin) at a dose of 1 L/ha (T4);
           
    The sowing scheme adopted was 40 cm between seed hole and 50 cm between ridges. The sowing rate adopted was 2 seeds per hole. Biopesticide treatments were carried out once a week from the 15th day after emergence. These treatments were stopped one week before harvesting.
           
    The synthetic chemical insecticide was applied twice according to what is recommended by the agriculture technical services: the first application was done 15 days after emergence and the second when the flower buds appeared. It was bought in a SPROCA store in Togo.
           
    Two liters of each formulation were applied on 7.5 m2 area for every treatment.
     
    Biopesticide formulation
     
    Formulations were carried out by mixing E. globulus essential oil with a solution of potassium palmitate in proportions of 75% and 25% (v/v), respectively. The essential oil of E. globulus used is obtained from the leaves; it contains p-Cymene (23.38%), D-Limonene (12.16%), l,8-cineole (24.47%) and ã- Terpinene (29.91%) as the major compounds (Bokobana et al., 2022). The 5% concentration of potassium palmitate solution was used as an emulsifier to facilitate dilution with water and ensure stable emulsions.Table 1 illustrates the composition of 2 liters of biopesticide solution sprayed on an elementary plot measuring 7.5 m2.

    Table 1: Composition of 2 L of biopesticides solution sprayed.


     
    Observation and data collection
     
    Aphids were identified using the identification keys of Blackman and Eastop (2000). Data collection consisted of:                                                                                          
    - Weekly counts (once a week) of larvae and adults of A. craccivora on ten (10) randomly selected plants of each treatment, which were marked. On each plant selected and marked, aphids were counted on the five (5) subterminal leaves (Denéchère, 1981) and before the phytosanitary treatments. When larvae were present on the leaves, a 4.9 cm2 magnifying glass was used for observation. Data collection began on the 15th day after emergence of plant. 
    - Counting the number of pods on ten plants selected previously per treatment at the harvest period.
     
    Statistical analysis
     
    The results obtained were analysed using XLSTAT version 2021.2 software. The results were analyzed using the analysis of variance (ANOVA) procedure and the treatment means were compared by Duncan test at the 0.05 probability level. The curves and histograms were drawn using Excel.

    RESULTS AND DISCUSSION

    Effect of treatments on dynamic of A. craccivora population
     
    Firstly, the period from 15 to 22 days after emergence is characterised initially by an increase of aphid numbers in each plot, with a higher level in the control plot (79.2 aphids per plant). From 22 to 56 days after emergence, we noted generally a decrease in aphid numbers in all treatments, despite the up-and-down variations of average number of these aphids before 56 days after emergence (Fig 1).

    Fig 1: A. craccivora population dynamics depending on different treatments.


           
    The average numbers of A. craccivora per plant during the experimentation are shown by Fig 2.

    ​

    Fig 2: Average number of aphids per plant depending on different treatments.


           
    Discrimination of the means using Duncan’s test at the 5% threshold shows 3 homogeneous groups, revealing a significant difference between the results obtained. The analysis shows that the average numbers of aphids per plant obtained in treatments T3 and T4 are statistically identical to each other, but statistically different from the average numbers of aphids obtained in the other treatments.
           
    The formulation became increasingly effective in reducing the A. craccivora population density as the essential oil concentration increased. A high concentration of E. globulus essential oil implies the presence of an important quantity of active molecules to which the target insects are sensitive, thus increasing the efficacy of the bioinsecticide; these biomolecules, mostly monoterpenes such as p-Cymene, D-Limonene, l,8-cineole and γ-Terpinene (Bokobana et al., 2022) have a neurotoxic effect; they interfere with the neuromodulator octopamine and GABA chloride channels (Priestley et al., 2003; Jankowska et al., 2018). The effect of treatments on these pests would depend on the nature of the insecticide and its active ingredient concentration. In the case of our study, the synthetic chemical insecticide (K-optimal (Acetamiprid-Lamdacyhalothrin) and the bioinsecticide at a concentration of 1% (T3) reduced significantly the population density of A. craccivora compared to the control. In general, bioinsecticides based on the essential oil of plant are less persistent than synthetic chemical insecticides due to the highly volatile nature of the active ingredients they contain (Isman, 2008; Mehinto et al., 2015). The reduction of the population density of A. craccivora by this formulation would be effected by an insect repellent and insecticidal action of the different substances tested.
     
    Effect of different treatments on pod yields
     
    Discrimination of means using Duncan’s test at the 5% threshold reveals two homogeneous groups. Analysis of these homogeneous groups shows that there are no significant differences between the average number of pods obtained in treatments T0 and T1; nor between the average number of pods obtained in treatments T2, T3 and T4, which represent the highest numbers (Table 2).

    Table 2: Average number of pod per plant.


           
    An increase of cowpea pod production compared with the control was obtained in relation to the essential oil concentration increase. The highest mean number of pods was obtained in plots treated with the synthetic chemical insecticide and the biopesticide formulation at concentrations of 0.5% and 1%. The average number of pods obtained in plots treated with the synthetic chemical insecticide (14.4±0.8) was statistically identical to the numbers obtained in plots treated with the 0.5% and 1% concentration formulations (12.4±1.4 and 12.425±1.16, respectively). According to Vaissayre and Cauquil (2000), a low density of biting-sucking insects on plant reduces the quantity of sap ingested and the transmission of viruses. Insecticide treatments, by reducing the aphid population density on plant, therefore ensure good growth and pod productivity.
           
    Pesticide formulations based on essential plant oils are potential alternatives to synthetic chemical pesticides. This study reports for the first time the efficacy of a pesticidal formulation based on the essential oil of E. globulus in the protection of cowpea crops against A. craccivora. E. globulus essential oil has most often been used in the formulation of pharmaceutical products in the medical field (Singh et al., 2021; Majeed et al., 2024); but nowadays there are also formulations based on E. globulus extracts used in plant protection. This is the case of a natural formulation used to combat potato mildew (Picaud, 2019).
           
    There are biopesticides based on plant extracts which are also effective against Aphis craccivora aphids on cowpeas. This concerns two Wettable Powder formulation based on Polygonum hydropiper flowers and Nicotiana tabacum leaves; these formulations have shown more than 65% effectiveness against these aphids (Gosh, 2024).
           
    Studies have revealed the pesticidal properties of formulations based on other botanical extracts from tropical flora against crop pests (Bambara and Tiemtoré, 2008; Ramadass  and Thiagarajan, 2021; Semako et al., 2021; Sane, 2021); among the plant species used for formulation, the use of Azadirachta indica organs appears to be one of the most popular (Adhikari et al., 2020).
           
    It’s important to note that the use of plant extracts over large areas can lead to massive destruction of the plants, so it’s important to plan for their replacement or replanting.

    CONCLUSION

    The aim of this study was to reduce the use of synthetic chemical pesticides by promoting the use of biopesticides in the management of the main pests of cowpea (V. unguiculata), such as A. craccivora. The results obtained showed that the toxicity of the essential oil is depending on concentration. Treatment with the synthetic chemical insecticide showed comparable effects with the high concentration of bioinsecticide. The high concentration formulation of E. globulus essential oil reduced considerably aphid population density per plant compared to the control and improved pod production. E. globulus essential oil can therefore be used as an active raw material in the formulation of biopesticides. One problem still to be resolved with bioinsecticides based on essential oil is their high volatility. It would therefore be necessary to develop strategies to resolve these problems for more sustained protection of the environment while ensuring high crop productivity.
     
    Disclaimers
     
    The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

    CONFLICTS OF INTEREST

    All authors declare that they have no conflict of interest.

    REFERENCES


    1. Adesina, J.M. and Enudeme, D.C. (2018). Insecticidal Efficacy of Some Plant Aqueous Extracts Mixtures against Post Flowering Insect Pest of Cowpea. 36th Annual Conference of Horticultural Society of Nigeria. Nasarawa State, Nigeria: Horticultural Society of Nigeria.

    2. Adhikari, K., Sudip, B., Dikshya, N., Jiban, S. (2020). Use of neem (Azadirachta indica A. Juss) as a biopesticide in agriculture: A review. Journal of Agriculture and applied biology. 1(2): 100-117. doi: https://doi.org/10.11594/jaab.01.02. 08.

    3. Akantetou, P.K., Tozoou, P., Bokobana, M.E., Nadio, N.A., Kilimou, P., Koba, K., Poutouli, W., Sanda, K. (2021). Effets de la fumure minérale et des prédateurs sur le niveau d’infestation du cotonnier par le puceron (Homoptera: Aphididae) au Togo. African Crop Science Journal. 29(1): 13-30. https:// doi.org/10.4314/acsj.v29i1.2.

    4. Akello, J. and Sikora, R. (2012). Systemic acropedal influence of endophyte seed treatment on Acyrthosiphon pisum and Aphis fabae offspring development and reproductive fitness. Biological control. 61(3): 215-221. https://doi. org/10.1016/j.biocontrol.2012.02.007.

    5. Bambara, D. and Tiemtoré, J. (2008). Efficacité biopesticide de Hyptis spicigera Lam., Azadirachta indica A. Juss. et Euphorbia balsamifera Ait. sur le niébé Vigna unguculata L. Walp. Tropicultura. 26(1): 53-55.

    6. Blackman, R.L. and Eastop, V.F. (2000). Aphid on the World’s Crops: An Identification Information Guide, 2nd Edition. John Wiley and Sons, Chichester.

    7. Bokobana, E.M., Nadio, N.A., Eloh, K., Akantetou, P., Tozoou, P., Koba, K., Sanda, K. (2022). Insecticidal activity of the essential oil of Eucalyptus globulus Labill. (Myrtaceae) on Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) and Tribolium castaneum Herbst, corn pests in storage. International Journal of Green and Herbal Chemistry. 11(2): 193-200. doi: 10.24214/ijghc/gc/11/2/19300.

    8. Bonnemain, J.L. and Chollet, J.F. (2003). L’arsenal phytosanitaire face aux ennemis des plantes. Considérations générales. Comptes Rendus Biologies. 326(1): 1-7. doi: 10.1016/ S1631-0691(03)00014-3.

    9. Denéchère, M. (1981). Note sur la distribution et l’évaluation des populations d’Aphis gossypii Glov. Coton Fibres tropicales. 36(3): 271-180.

    10. DSID. (2017). Caractéristiques structurales de l’agriculture togolaise. Rapport principal. Direction des Statistiques Agricoles, de l’Informatique et de la Documentation, Lomé. p.72.

    11. FAO. (2025). Food and Agriculture Organization Statistical Database. Retrieved from https://www.fao.org/faostat/en/?and data.)#data/QCL.

    12. Gbekley, H.E., Katawa, G., Karou, S.D., Anani, S., Tchadjobo, T., Ameyapoh, Y., Batawila, K., Simpore, J. (2017). Ethnobotanical study of plants used to treat asthma in the maritime region in Togo. Afr. J. Tradit. Complement Altern. Med. 14(1): 196-212. doi: 10.21010/ajtcam.v14i1.22.

    13. Ghedira, K. (2025). Eucalyptus globulus Labill. (Myrtaceae). Phytothérapie. 23(1): 25-31. doi: 10.3166/phyto2025-0442.

    14. Ghosh, S.K. (2024). Bio-efficacy of plants based formulations for the management of cowpea aphid (Aphis craccivora Koch.). Legume Research. 47(2): 284-290. doi: 10.18805/LR-4636.

    15. Gomes, A.M.F., Nhantumbo, N., Ferreira-Pinto, M., Massinga, R., Ramalho, J.C. and Ribeiro-Barros, A. (2019). Breeding elite cowpea [Vigna unguiculata (L.) Walp] varieties for improved food security and income in Africa: Opportunities and challenges, in Legume Crops-Characterization and Breeding for Improved Food Security. London, United Kingdom: IntechOpen, 62-640. doi: 10.5772/intechopen. 84985.

    16. Harris, R. (2003). Synergism in the essential oil world. International Journal of Aromatherapy. 12: 179-186. https://doi.org/ 10.1016/S0962-4562(02)00083-8.

    17. Ibro, G., Sorgho, M.C., Idris, A.A., Moussa, B., Baributsa, D., Lowenberg- DeBoer, J. (2014). Adoption of cowpea hermetic storage by women in Nigeria, Niger and Burkina Faso. Journal of stored products research. 58: 87-96. https://doi.org/ 10.1016/j.jspr.2014.02.007

    18. Isman, M.B. (2008). Problèmes et perspectives de commercialisation des insecticides d’origine botanique, pp. 465-476. In: C. Regnault-Roger, J.R. Bernard et C. Vincent (Eds), Biopesticides d’origine végétale - 2ème edition. Tec and doc, Paris, France.

    19. Jankowska, M., Wyszkowska, J., Stankiewicz, M., Rogalska, J. (2018). Molecular targets for components of essential oils in the insect nervous system-A Review. Molecules. 23(1): 34-53. https://doi.org/10.3390/molecules23010 034.

    20. Kim, D.K., Ochar, K., Iwar, K., Ha, B.K., Kim, S.H. (2025). Cowpea (Vigna unguiculata L.) production, genetic resources and strategic breeding priorities for sustainable food security: A review. Front. Plant Sci. 16: 1562142. doi: 10.3389/fpls.2025.1562142.

    21. Labdelli, F., Bousmaha, F., Mazrou, K., Moulay, M., Adamou-Djerbaoui, M., Rabahi, H. (2022). Insecticidal effect of eucalyptus essential oils on mortalities of storage pests of grains Sitophilus oryzae and Sitophilus granarius in the region of Tissemsilet Algeria. Indian Journal of Agricultural Research. 56(6): 755-758. doi: 10.18805/IJARe.A-661.

    22. Majeed, H., Iftikhar, T., Nadeem, M., Nazir, M. (2024). Green synthesis of Eucalyptus globulus zinc nanoparticles and its use in antimicrobial insect repellent paint formulation in bulk industrial production. Heliyon, 10: e24467. https://doi.org/ 10.1016/j.heliyon.2024.e24467.

    23. Manda, J., Alene, A.D., Tufa, A.H., Feleke, S., Abdoulaye, T., Omoigui, L.O. (2020). Market participation, household food security and income: The case of cowpea producers in northern Nigeria. Food Energy Secur. 9: e211. doi: 10.1002/fes3.211.

    24. Mario, M.B., Astuti, L.P., Hsu, J.L. and Kafle, L. (2021). Fumigant activity of four plant powders against cowpea weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae) in Stored Adzuki Bean. Legume Research. 44(6): 667-672. doi: 10.18805/LR-533.

    25. Mehinto, J.T., Atachi, P., Elégbédé, M., Kpindou, O.K.D., Tamo, M. (2015). Efficacité comparée des insecticides de natures différentes dans la gestion des insectes ravageurs du niébé au Centre du Bénin. Journal Applied Bioscience. 84: 7695-7706. https://doi.org/10.4314/jab.v84i1.1.

    26. Nadio, N.A., Gmasson, G., Bokobana, E.M., Akantetou, P.A., Poutaouli, W., Koba, K., Sanda, K. (2023). Effet Larvicide de l’Huile Essentielle d’Eucalyptus globulus Labill. (Myrtaceae) sur Pectinophora gossypiella S. et Thaumatotibia leucotreta M. (Lepidoptera), Ravageurs Carpophages du Cotonnier au Togo. European Scientific Journal. 19(30): 181-199. https://doi.org/10.19044/esj.2023.v19n30p181.

    27. Picaud, T. (2019). Formulation naturelle innovante à base d’extrait d’Eucalyptus globulus permettant de gérer le mildiou de la pomme de terre. Brevet d’invention belge BE1025821B1.

    28. Priestley, C., Williamson, E., Wafford, K., Sattelle, D. (2003). Thymol, a constituent of thyme essential oil, is a positive allosteric modulator of human GABA (A) receptors and a homo- oligomeric GABA receptor from Drosophila melanogaster. British Journal of Pharmacology. 140(8): 1363-1372. https://doi.org/10.1038/sj.bjp.0705542.

    29. Ramadass, M. and Thiagarajan, P. (2021). Current Trends and Emerging Technologies for Pest Control Management of Rice (Oryza sativa) Plants, pp. 125-179. In: K.M. Gothandam, R. Srinivasan, S. Ranjan, N. Dasgupta, E. Lichtfouse (eds), Environmental Biotechnology, Volume 4, Environmental Chemistry for a Sustainable World, 68. Springer, Cham., New York, USA. 

    30. Sane, B. (2021). Efficacité biologique des extraits d’Azadirachta indica A. Juss, Hyptis suaveolens (L.) Poit et Anacardium occidentale Linn. dans la lutte contre Helicoverpa armigera (Hübner, 1808) (Lepidoptera, Noctuidae) ravageur du cotonnier (Gossypium hirsutum L.) au Sénégal. Thèse de doctorat, Université Cheikh Anta Diop, Dakar.

    31. Semako, A.G., Aboudou, K., Chatigre, K.O., Noukpozounkou, M.S.P., Soumanou, M.M. (2021). Optimisation in vitro de l’efficacité des biopesticides dans la lutte contre les principaux ravageurs du niébé par la méthode des surfaces de réponse. International Journal of Biological and Chemical Sciences. 15(1): 41-53. https://dx.doi.org/10.4314/ijbcs. v15i1.5.

    32. Sharma, S., Sushma. and Nishtha. (2021). A Review on Eucalyptus Globulus-An Authentic Herb. Journal of Pharmaceutical Research International. 33(53B): 107–114. doi: 10.9734/ jpri/2021/v33i53B33686.

    33. Singh, G., Khan, M.W., Ahirwar, C.S., Gupta, V. and Soni, K. (2021). Formulation and Biological Implication of Eucalyptus globulus and Trachspermum ammi Organogel for Topical Delivery. International Journal of Current Research. 13(12): 19790-19793. https://doi.org/10.24941/ijcr.426 06.12.2021.

    34. Vaishna, T., Radhakrishnan, V.V. and Resmi, L. (2025). Genetic diversity of cowpea: implications for crop Improvement and food security: A Review. Agricultural Reviews. 1-8. doi: 10.18805/ag.R-2866.

    35. Vaissayre, M. and Cauquil, J. (2000). Principaux ravageurs et maladies du cotonnier en Afrique au sud du Sahara. CIRAD, Montpellier, France.
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