Impact of Trichogramma chilonis, egg parasitoid in management of rice leaf folder, Cnaphalocrocis medinalis and validation at farmer field

Introduction

Rice (Oryza sativa) is the most important cereal crop in the developing world and is the staple food of over half of the world's population including all of East and Southern Asia (Yu et al., 2020) [28] . In India, area under rice cultivation is 51.27 million hectares, production of 150.18 million tonnes with productivity of 2929 kg/ha in year 2024-25 (Anonymous, 2025 A) [1] . India exported a total of 20.19 MT rice, earning a massive foreign exchange of Rs. 1,05,722 crores till February 2024. In Haryana, rice is cultivated on 1.83 million hectares with production of 7.13 million tonnes and productivity of 3.88 tonnes/ha (Anonymous, 2025 B) [2] . The adoption of high-yielding varieties, the inclusion of modern agronomic practices, and monoculture in extensive areas, combined with humid conditions, promote the rapid growth of insect pests (Kraker et al., 2000, Reddy, 2013) [11,19] . As the rice crop is grown worldwide in a wide variety of ecosystems and soil conditions, it becomes a favorable host for a diverse assortment of insects and pathogens from the nursery to harvest. However, only a small number of them are regarded as significant pests that result in losses by reducing yield. Among these Insect-pests, the rice leaf folder, C. medinalis Guenee, is of significant importance due to its capacity to deplete chlorophyll from the leaves, resulting in a substantial decline in crop yield. The rice leaf folder poses a considerable threat as a primary foliage consumer. This pest is highly detrimental across all rice-growing environments in Asia, causing yield reductions ranging from 30 to 80% during severe outbreaks (Gangwar, 2015) [6] . Its prevalence has extended to nearly all rice cultivation regions throughout the country (Krishnaiah and Varma, 2011) [12] . The management of rice leaf folder using synthetic chemicals has not proven to be an effective venture due to insecticide resistance, pest resurgence, and its contribution to environmental pollution (Mahal et al., 2006) [16] . Due to concerns about the longterm ecological impact of synthetic pesticides and their potential harm to human health (Linka et al., 2005) [15] , as well as to beneficial insects (Youn et al., 2003) [27] , and domestic animals, natural approaches to pest control have been the subject of renewed research. This resurgence of interest includes the use of safe, effective and environmentally acceptable bio-intensive methods. The awareness for the consumption of ecologically safe food has provided impetus to organic farming in India and intensive efforts have been made to find out alternate methods of pest control (Nathan et al., 2004) [18] . An ecologically sound strategy, i.e. use of biocontrol agents was felt necessary for developing pest management practice through successive releases of biocontrol agents in the genus Trichogramma (Hymenoptera: Trichogrammatidae) have been widely used for biological control of lepidopteran insect pests (Ko et al., 2014) [10] . Augmentative releases of T chilonis (Ishii) and T. japonicum (Ashmead) @ 1,00,000 each have been found effective for the biological suppression of yellow stem borer, S. incertulas and leaf folder, C. medinalis in organic rice (Sangha, K. S. et al., 2018) [21] . Therefore, evaluation of bio-efficacy T. chilonis against leaf folder in rice was carried out at CCS HAU Rice Research Station, Kaul to promote and increase acceptance at farmers' level.

Materials and Methods

Management of leaf folder in rice using egg parasitoid T. chilonis in basmati rice (var. PB 1121) was conducted at Rice Research Station, Kaul, Geographically, located at 29º 51' 29.5' N latitude and 76º 39' 24.3' E longitude at an elevation of 241 meters above mean sea level in the North-Western part of the Haryana. PB1121 was transplanted during second week of July in plots size of 50 sq.m. (10x5 m 2 ) with three replications in spacing of 20x15cm during both the years (2022 and 2023). Each plot was separated by 3 m² of non-experimental area to avoid inter-plot movement of released parasitoid. Experimental field was maintained with recommended package of practices except plant protection measures. Six different augmentative releases of T. chilonis were made starting from 20 days after transplanting (DAT) and was compared with untreated control. Tricho-cards were procured from Bio-control lab at Regional Research station, (Uchani)Karnal. Each Tricho-card was cut into small strips so as to obtain 10 parasitized eggs per strip and stapled uniformly to the underside of the leaves in all treatments. Following treatments were used to check relative efficacy of egg parasitoid, T. chilonis for control of rice leaf folder:

Observations recorded

Leaf folder infestation was recorded at 10 days' interval starting from 20 days after transplanting (DAT). Total leaves and damaged leaves were recorded to compute per cent damaged leaves with the following formulae:

Per cent damaged leaves = Number of damaged leaves × 100 Total number of leaves Effects on natural enemy's population was also recorded from 10 randomly selected hills/plot after each application and pooled later.

Grain yield of the crop was recorded at harvest from all plots/replication and converted into q/ha. Farmers' field trial: Adaptive trials were carried out at 5 multilocations in districts Kaithal, Jind and Karnal during Kharif, 2024. Plot size for treated and untreated control was one acre each. Egg parasitoids, T. chilonis were released @ 50,000/acre at 30, 40, 50 and 60 Days after transplant rice crop. Observations were recorded on per cent leaf infestation by leaf folder from 5x5 m plot at three locations per trial. Total leaves and infected leaves per 10 plants were counted for leaf folder. Grain yield q/acre was recorded at harvest.

Statistical analysis:

The data was statistically analysed with analysis of variance using OPSTAT Software (Sheoran et al., 1998) [24] . [8] when T. chilonis and T. japonicum @ 100,000 was augumentatively released for the biological suppression of yellow stem borer and leaf folder in organic rice. Different doses of T. chilonis, viz., 50,000, 75,000, 100,000, 125,000 and 150,000 parasitized eggs per hectare were tried by Chhavi et al., 2019 [5] and reported maximum control when 150,000 parasitized eggs per hectare were released. Egg releases of Trichogramma sp. @ 100000 and 1250000 per hectare significantly reduced leaf folder infestation (Sagheer et al., 2008) [20] . Highest egg parasitization of leaf folder eggs due to release of T. chilonis @ 1 lakh parasitoids/ha for six times was also reported by (Mose et al., 2018) [17] .

Results and Discussion

Results similar to rice research farms were obtained at farmers' field. Where in all treated fields mean damage ranged from 6.42-6.57% while in untreated damage ranged from 12.37-12.77%. Reduction in treated was 47-48% over the untreated plots (Table 2). The efficiency of T. japonicum and T. chilonis reported by Kumar and Khan (2005) [13] on tiller damage and folded leaves varied from 78.1% to 81.6% from 72.6 to 81.8%, respectively, where egg parasitoids were released @ 1,00,000/ha in rice ecosystem. Earlier works Lakshmi et al., 2010 [14] ; Chakraborty, 2012 [4] ; Varma et al., 2013 [25] ; Vennila et al., 2018 [26] ; Sharmistha et al. 2020 [23] ; Sankeerthana et al., 2025 [22] ) report frequent multispecies parasitization of single egg masses and highlight T. schoenobii, T. dignus, T. japonicum, T. chilonis and T. rowani as key contributors. Significantly higher yield was observed in all the treatments as compared to control. In treatment T 6 increase in yield as compared to control was 23.82% during Kharif 2023(Table 3). However, increase in yield was highest 28.08% in chemical spray treatment as compared to other treatments (Table 3). Under farmer filed conditions highest increase in yield observed was 15.50% as compared to untreated (Table 2). Khan et al. (2005) [9] reported that the increase in paddy yield after inundative releases of T. chilonis, over control, ranged from 33.0 to 89.5 kg per acre. Six releases of T. chilonis and T. japonicum each @ 1,00,000/ha starting from 30 days after transplanting (DAT) resulted in lower incidence of rice leaf folder and stem borer and higher grain yield in organic basmati rice during 2014 and 2015, respectively over untreated control (Sangha et al., 2018) [21] . Karthikeyan et al.

(2007) [7] also reported that parasitoid releases in paddy resulted higher grains yield by 25.79-45.13% over insecticide treated plots.

DAT-Days after transplanting

Among natural enemies, highest population of spiders followed by dragonfly/damselfly and coccinellids was observed during both the years. No mirid bug was recorded in any treatment in both years. During, both the year, no effect on natural enemies was seen in any treatment (Table 4.). Higher natural enemies' population (lady bird beetles and spider) was reported in ecological engineering, IPM and farmer's practices (Baliyan, U. et al., 2025) [3] .

Conclusion

It is concluded from present study that releases of T. chilonis parasitized eggs at fixed intervals were effective in managing rice leaf folder (C. medinalis) in basmati rice. Releases of 50,000 parasitized eggs per acre, initiated at 30 DAT and repeated at every 10 days' interval, significantly reduces leaf folder incidence. It is pertinent to mention here that pest population remain below economic threshold level during both years. On the basis of result so achieved at research farms, experiment was recommended at farmer fields with 50000 parasitized eggs released at same intervals and found significant reduction in pest population as compared with untreated. Based on results it is recommended that T. chilonis can be an effective, and sustainable alternative to insecticides for the management of rice leaf folder in basmati rice. This technology is safe for non-target insects, natural enemies and best fit in integrated pest management (IPM).

Acknowledgement

AcknowledgmentAuthors are highly thankful to Regional Director, CCS HAU, Rice Research Station, Kaul (Kaithal) for providing all necessary support for conducting this experiment. And also thankful to farmers who cooperates during the research.

References

1. Anonymous. Agricultural Statistics at a Glance 2024-25. 2025. https://www.agriwelfare.gov.in/Documents/CWWGDATA/ Agricultural_Statisitcs_at_a_Glance_2024_25_2.pdf
2. Anonymous. Annual Report 2024-25. 2025. https://agriwelfare.gov.in/Documents/AR_Eng_2024_25.pd f
3. Baliyan U, Saini S, Yadav S, Panwar L, Madaan S. Ecofriendly management strategy for rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) control under laboratory conditions. Biopestic Int. 2025;21:123-128. https://doi.org/10.59467/BI.2025.21.123
4. Chakraborty K. Relative composition of egg parasitoid species of yellow stem borer Scirpophaga incertulas (Walker) in paddy field at Uttar Dinajpur, West Bengal, India. Current Biotica. 2012;6(1):42-52.
5. Chhavi, Pawan K, Sharma A, Srivastava A. Field efficacy of Trichogramma chilonis against rice leaf folder, Cnaphalocrocis medinalis in Kangra Valley of Himachal Pradesh. J Entomol Zool Stud. 2019;7(1):600-603.
6. Gangwar RK. Life cycle and abundance of rice leaf folder, Cnaphalocrocis medinalis (Guenee): A review. J Nat Sci Res. 2015;5:103-105.
7. Karthikeyan K, Jacob S, Purushothaman SM. Field evaluation of egg parasitoids, Trichogramma japonicum Ashmead and T. chilonis Ishii, against rice yellow stem borer and leaf folder. J Biol Control. 2007;21:261-265.
8. Kaur R, Brar KS. Evaluation of different doses of Trichogramma species for the management of leaf folder and stem borer on basmati rice. J Biol Control. 2008;22(1):131135.
9. Khan RA, Khan JA, Jamil FF, Ahmad M. Resistance of different basmati rice varieties to stem borers under different control tactics of IPM and evaluation of yield. Pak J Bot. 2005;37(2):319-324.
10. Ko K, Liu Y, Hou M, Babendreier D, Zhang F, Song K. Evaluation for potential Trichogramma strains for control of the striped stem borer in the Greater Mekong Subregion. J Econ Entomol. 2014;107(3):955-963.
11. Kraker J, Rabbinge R, Van Huis A, Van Lenteren JC, Heong KL. Impact of nitrogenous fertilization on population dynamic and natural control of rice leaf folders. Int Pest Manage. 2000;46:225-235.
12. Krishnaiah K, Varma NRG. Changing insect pest scenario in the rice ecosystem: A national perspective. Rice Knowl Manag Portal. 2011:1-28.
13. Kumar S, Khan MA. Bio-efficacy of Trichogramma spp. against yellow stem borer and leaf folder in rice ecosystem. Ann Pl Prot Sci. 2005;13:97-99.
14. Lakshmi VJ, Surekha K, Pasalu IC. Parasitization of rice yellow stem borer, Scirpophaga incertulas (Walker) egg masses. Annals of Plant Protection Sciences. 2010;18(2):366-369.
15. Linka B, Gabrioa T, Zoellnera I, Piechotowskia I, Paepkeb O, Herrmannb H, et al. Biomonitoring of persistent organochlorine pesticides, PCDD/PCDFs and dioxin-like PCBs in blood of children from South West Germany (Baden-Wuerttemberg) from 1993 to 2003. Chemosphere. 2005;58:1185-1191.
16. Mahal MS, Kajal VK, Kaur R, Singh R. Integration of chemical and biocontrol approaches for the management of leaf folder and stem borer on basmati rice. J Biol Control. 2006;20(1):1-6.
17. Moses S, Misra AK, Kishor DK, Kumar P. Egg parasitization of yellow stem borer and leaf folder of rice under prevailing weather parameters. Int J Curr Microbiol App Sci. 2018;7(12):2385-2391. https://doi.org/10.20546/ijcmas.2018.712.270
18. Nathan SS, Chung PG, Murugan K. Effect of botanical insecticides and bacterial toxins on the gut enzyme of the rice leaffolder Cnaphalocrocis medinalis. Phytoparasitica. 2004;32:433-443.
19. Reddy PP. Recent advances in crop protection. Dordrecht: Springer; 2013.
20. Sagheer M, Ashfaq M, Mansoor-ul-Hasan, Rana SA. Integration of some biopesticides and T. chilonis for sustainable management of rice leaffolder. Pak J Agri Sci. 2008;45:69-74.
21. Sangha KS, Shera PS, Sharma S, Kaur R. On-farm impact of egg parasitoid, Trichogramma spp. against lepidopteran pests in organic basmati rice. J Biol Control. 2018;32:116-120.
22. Sankeerthana A, Krishnakripa AM, Karkute SG, Golive P, Chatterjee M. Egg parasitoids of rice yellow stem borer Scirpophaga incertulas (Walker): Taxonomic identification and molecular characterization from West Bengal, India. Indian Journal of Entomology. 2025:e25967. https://doi.org/10.55446/IJE.2025.2967
23. Sharmitha T, Leo Justin CG, Joyce Roseleen SS, Yasodha P. Natural parasitism of yellow stem borer eggs in rice ecosystem at Tiruchirappalli. Entomon. 2020;45(3):181188. https://doi.org/10.33307/entomon.v45i3.549
24. Sheoran OP, Tonk DS, Kaushik LS, Hasija RC, Pannu RS. Statistical software package for agricultural research workers. In: Hooda DS, Hasija RC, editors. Recent advances in information theory, statistics and computer applications. Hisar: Department of Mathematics and Statistics, CCS Haryana Agricultural University; 1998. p. 139-143.
25. Varma NRG, Jagadeeshwar R, Shanker C. Relative composition of egg parasitoids of rice yellow stem borer Scirpophaga incertulas (Walker). Journal of Rice Research. 2013;6(2):53-58.
26. Vennila P, Sridevi G, Padmakumari AP. Effect of insecticides on parasitism by egg parasitoids of the rice yellow stem borer, Scirpophaga incertulas. Journal of Entomology and Zoology Studies. 2018;6(5):67-70.
27. Youn YN, Seo MJ, Shin JG, Jang C, Yu YM. Toxicity of greenhouse pesticides to multicolored Asian lady beetles, Harmonia axyridis (Coleoptera: Coccinellidae). Biol Control. 2003;28:164-170.
28. Yu S, Ali J, Zhang C, Li Z, Zhang Q. Genomic breeding of green super rice varieties and their deployment in Asia and Africa. Theor Appl Genet. 2020;133:1472-1482.