Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali

INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH AND ANALYSIS ISSN(print): 2643-9840, ISSN(online): 2643-9875 Volume 08 Issue 09 September 2025 DOI: 10.47191/ijmra/v8-i09-05, Impact Factor: 8.266 Page No. 4874-4880 IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4874 Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali Ana Maria Soares1, I Wayan Supartha2, Ketut Ayu Yuliadhi3 1Student of Master Program Agroecotecnologia, Faculty of Agriculture, Udayana University, Denpasar, Bali, Indonesia 2.3Integrated Pest Management Laboratory, Faculty of Agriculture, Udayana University, Denpasar, Bali, Indonesia ABSTRACT: Neotoxoptera Formosana Takahashi (Hemiptera: Aphididae) is an important pest in leaf onion plants and is also the cause of latent transmission of viruses in onion plants which currently has spread in various regions such as West Jawah, Central Jawah, Sumatra and Bali with attack intensity between 20 to 100%. The purpose of this study is to obtain predators that are effective in controlling N. formosana in all types of onion plants, especially leaf onions (Allium fistulosum L.) in Bali. The potential as a predator of N. formosana was carried out in two experimental stages, namely predator exploration, preference tests and functional responses to dominant predators. Predator exploration was conducted using survey method. The research was conducted in three districts in Bali (Denpasar, Tabana and Bangli) from May to July 2025. The exploration found 12 predator species, with Menochilus sexmaculatus (Coccinellidae) and Oxyopes salticus (Oxyopidae) as the dominant predator species. Preference tests showed that M. sexmaculatus larvae had a high predation rate of 8.83 per day, on N. formosana instar 4 and functional response tests showed O. salticus had a high predation rate of 44.00 within 24 hours at a prey density of 60 N. formosana instar 4, with a type I functional response pattern. Menochilus sexmaculatus (Coccinellidae) and Oxyopes salticus (Oxyopidae) are potential predator species in biological agent control of N. formosana aphids on spring onion plants in Bali. KEYWORDS: Neotoxoptera formosana, Leaf onion, Biocontrol. INTRODUCTION Neotoxoptera formosana (Takahashi) (Hemiptera: Aphididae) is one of the most important pests in all types of onion plants, especially in leaf onions. This pest was first discovered in Indonesia in August 1995 on onion plants in Pacet, Bogor, West Java (Rauf 2022). The problem of N. formosana pests is not limited to Indonesia, but also attacks many types of onion plants in various countries in ASEAN and Europe. Pest attacks on leaf onions, especially by the onion aphid Neotoxoptera formosana Takahashi, can result in huge losses for farmers because they reduce yields and the quality of the products produced (Nugroho et al., 2021). The cuthudaun N. formosana (Takahashi) (Hemiptera: Aphidae) is a serious threat to leek (Allium fistulosum L.) crops in Indonesia, especially in the Bali region. N. formossana control efforts commonly practiced by farmers have been the use of insecticides with an application frequency of 2-3 times per week throughout the growing season. Excessive use of insecticides is feared to have adverse effects such as the occurrence of pest resistance and resurgence, the emergence of secondary pests, the killing of natural enemies, environmental pollution and the danger of toxic residues for humans in general and especially for consumers of leeks. So it is necessary to explore and study the potential of natural enemies to control N. formosana in leaf onion plants that are safe and environmentally friendly. The purpose of this study is to obtain predators that are effective in controlling N. formosane in all types of onion plants, especially leaf onions (Allium fistulosum L.) in Bali. RESEARCH METHODS The research has been conducted in April - July 2025 which consists of two stages, the first stage explores the types of predators that have the potential as a biological control of N. formosana pest populations in leaf onion plants in three districts (Denpasar, Tabana, and Bangli) which are the centers of leaf onion and shallot production in Bali. The second stage of preference testing and functional response of dominant predator species found in the exploration that have high predatory power against Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4875 nymph and imago stadia of N. formosnan at the Integrated Pest Management Laboratory, Faculty of Agriculture, Udayana University Bali. Exploration of predators was carried out by directly collecting insects suspected as predators (predator estimation based on observations and literature studies). Predators that were tested for their preference for N. formosana were several predators that were commonly found and had a wide distribution from the results of exploration activities, namely predators Monochilus sexmaculatus, Oxypes salticus and larvae of M. sexmaculatus. Preference tests were conducted using the free-choice test method. The experiment was conducted using the method according to Legaspi et al. (2006). The experiment was carried out in plastic jars measuring 35 x 27 x 7 cm. In each jar, pieces of leeks containing N. formosana intar I, II, III, and IV nymphs were inoculated with 10 individuals each. The ends of the leek stalks were given wet cotton so that they would not wilt quickly. Next, one predator imago and larva was released right in the center of the petri dish, which had previously been fed for 24 hours. All treatments in the experiment were repeated 6 times. Observations of the number of aphids preyed upon were made for 12 hours after the release of the predators. Then the degree of preference (preference index) of the prey was calculated. This functional response test consisted of 5 treatments and 5 replications. Predation is done by inserting 1 individual predator insect that has been fed for 24 hours into a Petri dish that has contained prey with different amounts, namely as much as 5, 10, 20, 40, and 60, individuals for 5 replicates. Predator predation tests were conducted for 24 hours. Predatory ability was observed under direct laboratory conditions. Observations were made by counting the number of N. formosana preyed upon and compared to the density of prey provided. In addition, the time required by the dominant predator to deal with one prey was also calculated. These observations were made to determine the functional response of the dominant predator to N. formosana. Determination of the type of functional response is by using regression analysis, namely by calculating the number of N. formosana onion aphids that are preyed upon and compared with the density of the number of prey given. RESULTS Predator species with potential as biological control agents against Neotoxoptera formosana Takahashi in onion plants in Indonesia, especially in Bali. The inventory of predator species and the count of each predator species from the explorations are presented in Table 1. Based on the table, it appears that the predator species that are found in large numbers and have a wide distribution are Menochilus sexmaculata Fabricius and Oxyopes salticus, indicating that these two predatory insect species have the potential to be further studied and developed as biological agents for the natural control of N. formosana Takahashi aphids. Table 1. Number of predators caught on corn and chili commodities in the around leek plants in several production centers in Bali. No. Species Number Individuals Total Bangli Denpasar Tabanan 1. Micraspis discolor 0 15 0 15 2. Verenia Lineata Thunberg 0 38 0 38 3. Menochilus sexmachulata 0 146 0 146 4. Harmonia axyridis 0 20 0 20 5. Choelophora inagualis 0 12 0 12 6. Choelopora bisella Musland 5 1 2 8 7. Oxyopes salticus 10 34 15 59 8. Sirpidae 2 0 3 5 9. Reduvidae (Rhinocoris iracundus) 0 4 2 6 10. Harlequin 2 11 1 14 11. Calvia quatuordecimguttata 0 3 0 3 12. Chilocorus nihgrita 0 4 0 4 Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4876 Preferences and functional responses of dominant predators to nymph and imago stadia of Neotoxoptera formosana (Takahashi) on leek plants Based on the results shown in Figure 1, it can be seen that the dominant predators have different predation rates on nymphs and imago of N. formosana. Imago of M. sexmaculatus and O. salticus consistently preyed on N. formosana from the 1st instar to the 4th instar, while larvae of M. sexmaculatus were only seen preying on N. formosana from the 2nd to the 4th instar. Figure 1. Preying Power of Dominant Predators on Nymph and Imago Stadia of N. formosa Takahashi The results of the preference index test showed diverse preference values. Weak preference values (-1) of the three predators were shown at instar 1 to instar 2, but the preference index of M. sexmaculatus only showed a weak value at instar 1. M. sexmaculatur predator began to show its preference at instar 2 to instar 4, so the predation ability test of the three predators was taken at instar three of N. formosa. Table 2. Preference index of dominant predators towards nymph and imago stadia of Neotoxoptera formosana (Takahashi) on spring onion plants Predator Preference index value (Li) Instar 1 Instar 2 Instar 3 Instar 4 Oxyopes salticus -1 -1 0 0 Menochilus sexmaculatos -1 0 0 0 Menochilus sexmaculatus larvae -1 -1 0 0 Functional responses of O. saltcus, imago and larvae of M. sexmaculatus to N. formosana Prey density and type affect predator predation ability. An increase in the number of prey eaten by predators occurred as the prey density increased. All three predators ate the most prey at a prey density of 60 individuals and were statistically significantly different when compared to prey densities of 5, 10, 20 and 40 individuals of the same prey type (Table 3). The highest predation was shown by the larval predator M. sexmaculatus, which was able to prey on 43.60 individuals of N. formosa, followed Oxyopes salticus Menochilus sexmaculatos Menochilus sexmaculatus larvae Instar 4 Instar 3 Instar 2 Prey Instar 1 0.17 0.00 0.67 2.17 1.00 0.00 3.33 4.33 5.33 7.67 7.83 7.17 8.17 8.83 10.00 9.00 8.00 7.00 6.00 5.00 4.00 Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4877 by the predator O. salticus with 44.00 individuals, and M. sexmaculatos with 38.00 individuals. All three had almost the same ability to prey on N. formosa at all types of prey density (P > 0.05). The results showed that the three predators O. salticus, imago and larvae of M. sexmaculatus had high predation rates on N. formosa. As with predation ability, the three predators also had high predation rates and were significantly different (P < 0.05) across all prey densities tested (5, 10, 20, 40, and 60 individuals). Predation rates tended to be stable at low prey density and increased at high prey density (Table 4). Table 4.Predation rates of Oxyopes salticus, Menochilus sexmaculatos and Menochilus sexmaculatus larvae at different prey densities Predator predation rate (Mean±SB) Density Prey Oxyopes salticus Menochilus sexmaculatos Menochilus sexmaculatos larvae 5 Neotoxopter a formosana 0,003 ± 0,000 e 0,003 ± 0,000 e 0,003 ± 0,000 e 10 0,007 ± 0,000 d 0,007 ± 0,000 d 0,007 ± 0,000 d 20 0,011 ± 0,001 c 0,010 ± 0,001 c 0,010 ± 0,001 c 40 0,021 ± 0,001 b 0,018 ± 0,002 b 0,021 ± 0,001 b 60 0,031 ± 0,002 a 0,026 ± 0,002 a 0,030 ± 0,002 a The same letter in one column indicates there is no significant difference based on Tukey test at 5% real level. The functional response type was determined based on the highest R2value close to 1 from the regression analysis tested. The results of this study showed that the functional responses of O. salticus, as well as the imago and larvae of M. sexmaculatus, were classified as type I (R2= close to 1) in all prey types, with predation rates increasing or decreasing with increasing and decreasing prey density (Figure 2.) Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4878 Figure 2. Functional response types of Oxyopes salticus, Menochilus sexmaculatos, and Menochilus sexmaculatus larvae predators Based on the results of linear regression analysis, it can be seen that the functional response type of Oxyopes salticus, imago and Menochilus sexmaculatus larvae is classified as type I, with the value of r for each predator, namely r = 0.9982 in O. salticus, r = 0.9997 in M. sexmaculatus, and r = 0.9940 in M. sexmaculatus larvae (Table 5). The ability to prey on O. salticus, imago and larval M. sexmaculata N. formasana predators showed an increase with increasing prey density. Based on the results of linear regression analysis, it can be seen that the type of functional response of Oxyopes salticus, imago and Menochilus sexmaculatus larvae is classified as type I, with the value of r in each predator, namely r = 0.9982 in O. salticus, r = 0.9997 in M. sexmaculatus, and r = 0.9940 in M. sexmaculatus larvae (Table 5). The ability to prey on O. salticus predators, imago and larvae of M. sexmaculata N. formasana showed an increase with increasing prey density. Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4879 Table 5. Functional response types of O. salticus, M. sexmaculatus, and M. sexmaculatus larvae on N. formosa based on regression analysis and R2values Predator Regression equation R2value Functional response type Oxyopes salticus Linear regression y = 0.6986x + 1.9389 0,9982 I Menochilus sexmaculatos Linear regression 0,9997 I y = 0.5519x + 0.8626 Menochilus sexmaculatos larvae Linear regression 0,994 I y = 0.7019x + 1.6481 DISCUSSION Potential predators should have a high ability to compete, disperse, and a wide range of environmental tolerance. When there are no host plants in the field, predators must be able to disperse to non-host plant habitats (evacuate and find alternative prey). When the host plant is present, the predator must be able to quickly colonize the habitat de Bach (1991). Therefore, the dominant predator species in the explorations need to be further tested for their predatory power and preference for N. formosane to determine their effectiveness as biological agents in controlling N. formosane in leaf onions. Oxyopes salticus, imago and larvae of M. sexmaculata Fabricius instar 4 tested had high predatory power with each: M. sexmaculata larvae preyed on 8.83 N. formosana instar 4 aphids and Oxyopes salticus was able to prey on 8.17 N. formosana instar 4 aphid nymphs per day. Prabaningrum et al. (2005) reported that the predator M. sexmaculata was able to prey on as many as 20-40 B. tabaci larvae at the experimental level in the screen house. The results of preference testing presented in Table 2 indicate that the three predator species are different towards N. formosana. According to deBach (1991), natural enemies can select suitable hosts or prey and the selection takes place through natural processes. Frazer (1988) and Legaspi et al., (2006) stated that two important differentiators of host or prey range are host taxonomy and ecology. The results of this study indicate that the availability of prey greatly affects the predation ability of predators, the more prey the higher the predator's predation ability. The same results were also stated by Rachmalia (2013) and Wagiman (1997) in their research on the predation ability of the predator M. sexmaculatus against Aphis craccivora Koch showing that predators will prey more at higher prey densities compared to low densities. This relationship of predator predation ability to prey density is also explained in terms of functional response. As an essential component in the dynamics of interactions between predators and their prey, functional response is considered important in providing an overview of the effectiveness of predators in controlling prey populations (Nelly & Syuhadah 2012). Functional responses of O. salticus predators, imago and larvae of Menochilus sexmaculata in this study both showed type I. which means that the rate and ability of predation of O. salticus predators, imago and larvae of M. sexmaculata increased along with the increase in prey density. The increase in prey density is related to the ease with which predators can find their prey because predators and prey are in a limited space. This type I functional response generally occurs in laboratory experiments with one prey species provided (Van Alpen & Jervis 1996). Menochilus sexmaculatus instar 4 larvae have a type I or linear functional response where the amount of prey eaten is directly proportional to the amount of prey density. The ability to prey occurs at a prey density of 60 prey (Figure 2). According to Patel ((2015), the mean feeding ability of 1st instar larvae on A. cracivora was 20.7, instar 2 32.60, instar 3 and 4 39.60. This shows that the older the insect (instar), the more it needs to eat. This happens because the 4th instar larvae will change into pupae so that they need food reserves, which causes their food needs to increase. According to Purnomo and Nanang (2007), pupa is the phase where insects begin to be passive. CONCLUSIONS Menochilus sexmaculatus (Coccinellidae) and Oxyopes salticus (Oxyopidae) are potential predator species in biological agent control of N. formosana aphids on spring onion plants in Bali. Exploration and Evaluation of Potential Dominant Predators as a Candidate for Biological Control Agent Neotoxoptera Formosana (Takahashi) (Hemiptera: Aphididae) Onion Plants (Allium Fistulosum L) in Bali IJMRA, Volume 08 Issue 09 September 2025 www.ijmra.in Page 4880 REFERENCES 1) de Bach, P. (1991). Biological control by natural enemies (2nd ed.). Cambridge University Press. Frazer, BD 1988, 'Coccinellidae, in aphids scale insects; their biology, natural enemies and control, ed Minks, AK, Harrewijn, P (eds.). vol. B, New York, Amsterdam: Elsevier. pp. 231-47 2) Legaspi, JC, Simmons, AM, & Legaspi Jr, BC 2006, 'Prey preference by Delphastus catalinae (Coleoptera: Coccinellidae) on Bemisia argentifolii (Homoptera: Aleyrodidae): Effects of plant species and prey stages', Bioone Online J., no. 89, pp.21822. 3) Nelly, N. Trizelia. Q, Syuhadah. 2012. Functional Response of Menochilus sexmaculatus Fabricus (Coleoptera: Coccinellidae) to Aphis Gossypii (Glover) (Homoptera: Aphididae) at Different Age of Chili Plants. Indonesian Journal of Entemology. 9(1):23-31. doi: https:// doi.org/10.5994/jei.9.1.23. 4) Nugroho, W. A., Handayani, D., & Suharto, R. (2021). Damage and yield losses due to Neotoxoptera formosana infestation on leeks in West Java. Journal of Tropical Plant Pests and Diseases, 21(2), 105-112. 5) Patel, R, A. 2015. Feeding Potentiality of menochilus sexmaculatus Fab. On Different Aphid Species. Ijritcc, 3(7): 44264430. 6) Purnomo, H, and Nanang, T.H. 2007. Entomology. Jember. CssPress. 7) Rachmalia PK. 2013. Predation potential of Menochilus sexmaculatus F. (Coeloptera: Coccinelidae) against Aphis craccivora Koch. (Hemiptera: Aphididae) on long bean. Thesis. Bogor: Bogor Agricultural University. 8) Rauf, A. (2022). Distribution and impact of Neotoxoptera formosana on onion crops in Indonesia. 9) Vegetable Crops Research and Development Center, Technical Report. 10) Van Alphen JJM, Jervis MA. 1996. Foragingbehavior. In: Jervis M, Nkidd (Ed.), Insect Natural Enemies. Practicalapproaches to Their Study and Evaluation. pp. 1-62. Londong: Chapman and Hall Published. doi: https://doi.org/10.1007/978-94-0110013-7_1. 11) Wagiman F. 1997. Daily activity rhythm of Menochilus sexmaculatus preying on Aphis cracivora. In: Hidayat P et al., (Eds.) Papers presented at the Vth Etymology congress and Etymology Symposium, Indonesian Entemology Society (Bandung, June 24-26, 1997). pp. 24-26. Bandung: PEI. There is an Open Access article, distributed under the term of the Creative Commons Attribution – Non Commercial 4.0 International (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/), which permits remixing, adapting and building upon the work for non-commercial use, provided the original work is properly cited.