Bio-efficacy of insecticides against major insect pests of rice

Introduction

Rice, Oryza sativa (Linnaeus) is one of the important cereal crops, being the staple food for more than 65 per cent of the world population (Mathur et al., 1999) [15] . Which provides 15% of the global calorie's intake and feeds about 45% of the world population and the area of rice cultivation in India is 45.5 million ha, with production of 1308.37 lakh tones and a productivity was 41q/ha About 24% of the world's total rice production is grown in India (Anonymous, 2022) [1] . Rice and its cultivation are integral parts of humankind in and around the world. In efforts to end world hunger and malnutrition, rice is considered the most important crop with significant contributions to the world's primary food production (FAO,2022). More than half of the global rice production is shared by India and China. The primary challenge confronting rice scientists today is how to continually develop technologies that will eventually result in higher production to commensurate with the increasing population. India has surpassed China to become the world's most populous nation, with 142.86 crore inhabitants (UNFPA, 2023). India has the largest area while china is the largest producer of rice in the world. The Year 2004 was declared as "International Year of Rice". Asian countries grow and eat around 85% of the world's rice. Due to its lack of fat and cholesterol, rice is a healthy cereal a good meal to include in a balanced diet is rice. It is a good source of fiber, calcium (0.3 g/mg), iron (38 ppm), protein (7.2%), carbohydrates (78%) and vitamins and minerals such thiamine (2.8 g/g), niacin (29.6 g/g) and riboflavin (0.5 g/g). There is not much sugar in it. Due to its gluten-free nature, rice is a need for diabetics and other patients with gluten-free dietary requirements (Laskowski et al., 2019) [14] .

The state of Chhattisgarh is the 16th most populous and 10th largest in terms of area in India. It is also recognized as a major producer of rice 43 per cent of the state's total arable land is under cultivation, and about 70 per cent of the population works in agriculture. One of the main crops is paddy the geographical area is approximately 136 lakh ha, with 46.51 lakh ha of cultivable land and 60.76 lakh ha 2 of forest land (Jaiswal et al., 2023) [8] . Rice is one of the vital crops in Chhattisgarh state and Chhattisgarh is the sixth largest producer of rice with the production of 8 million tons contributing 6 per cent of the rice production of the country and forth largest state in terms of rice area contributing 8 per cent area of the country (Jambhulkar et al., 2024). Chhattisgarh is a state in central India. It is known for rice cultivation and called "Rice Bowl of India" rice occupies average of 3.6 million hectare with the productivity of the state ranging between 1.2 to 1.6 tons per hectare depending upon the rainfall (Jaiswal and Soni 2024) [8] . It is cultivated in almost all the tropical, subtropical and temperate countries of the world. One of the major constraints of rice production and low productivity in India is the occurrence of insect pests at various stages of the crop growth. The rice crop is subject to attack by more than 100 species of insects and 20 of them can cause economic damage (Pathak and Khan, 1994) [18] . The rice crop is subject to attack by more than 100 species of insects, of which approximately 20 can cause significant economic damage (Pathak and Khan, 1994) [18] . Among the major pests, yellow stem borer Scirpophaga incertulas (Walker) causes 25-70% yield reduction; gall midge Orseolia oryzae (Wood-Mason) causes 15-60% loss; leaf folder Cnaphalocrocis medinalis (Guenee) accounts for 10% loss; and whorl maggot Hydrellia sasakii contributes to early-season crop damage. Together, these pests account for approximately 70% of the total insect-related yield losses in rice (Dhurwey and Deole, 2021) [4] .

The present study was therefore undertaken to evaluate the comparative bio-efficacy of six insecticides representing different chemical groups and their economic viability against major insect pests of rice under Bastar Plateau conditions.

Material and Method

The field experiment was conducted at the Research cum Instructional Farm of Shaheed Gundadhur College of Agriculture and Research Station, Jagdalpur, Bastar (C.G.) -494001 during Kharif 2024. The experiment was laid out in Randomized Block Design (RBD) with seven treatments and three replications. Each plot size was 25 m². The rice variety Swarna was used as the test crop, transplanted at 20 cm × 15 cm spacing.Six insecticides treatment were evaluated against an untreated control: T 1 -Chlorpyriphos 20% EC @ 1 ml/l; T 2 -Chlorantraniliprole 18.5% SC @ 0.55 ml/l; T 3 -Lambda-cyhalothrin 5% EC @ 1.6 ml/l; T 4 -Carbosulfan 25% EC @ 1.2 ml/l; T5 -Tetraniliprole 18.18% SC @ 0.32 ml/l; T6 -Bifenthrin 10% EC @ 2.5 ml/l; T7 -Untreated control (water spray). Three sprays were applied at 25, 45 and 60 days after transplanting (DAT). Observations were recorded 3, 7 and 15 days after each spray. The per cent damage was calculated by using given formula:

For yellow stem borer per cent: The per cent incidence of yellow stem borer (S. incertulas) in term of dead heart and white ear head were recorded from 10 hills in each plot at tillering and panicle stages respectively.

Percentdead heart =

Numberofdead heart or white ear Total number of tillers × 100

For gall midgeper cent: Total number of tillers and damaged tillers (onion shoots) was counted on 10 randomly selected plants (hills) to calculate percentage of silver shoots (SS%)i.e., gall midge incidence Percentsilver shoot = Numberofsilver shoots Total number of tillers × 100

For leaf folderper cent: The incidence of leaf folder (C. medinalis) was observed in terms of leaf damage and the per cent damage was recorded from at randomly selected 10 hills in each replication.

Percentdamage = Numberofdamagedleaves

Total number of leaves × 100

Forwhorl maggotper cent:

The incidence of whorl maggot (H. sasakii) was observed in terms of leaf damage and the per cent damage was recorded from at randomly selected 10 hills in each replication.

Percentdamage = Numberofdamagedleaves

Total number of tillers × 100

Then, the pest intensity was scored as per standard evaluation system, International Rice Research Institute (IRRI)

Results and Discussion

Efficacy against Rice Stem Borer, Scirpophaga incertulas (Walker) All insecticidal treatments significantly reduced dead heart (DH) percentage compared to the untreated control at all spray intervals (Table 1 [2] , who reported superior and consistent efficacy of newer chemical groups including chlorantraniliprole against rice stem borer. Jaglan et al. (2023) [7] also observed that Chlorantraniliprole at 50 g a.i./ha resulted in only 1.43% WEH compared to 7.21% in untreated plots. Mishra et al.

(2024) [16] explained that diamide insecticides act as ryanodine receptor modulators causing rapid feeding cessation and prolonged muscle paralysis, justifying their strong field-level activity.

Efficacy against Rice Gall Midge, Orseolia oryzae (Wood-Mason) All insecticidal treatments significantly suppressed silver shoot (SS) incidence compared to the untreated control at all observation intervals ( [20] reported that repeated applications of pyrethroid insecticides, particularly bifenthrin, resulted in markedly lower SS incidence (2.5-5.6%) due to strong contact toxicity and rapid knockdown of newly hatched larvae. Kumar et al. (2023) [11] also confirmed that carbosulfan consistently recorded lower silver shoot incidence through its systemic and contact action targeting maggots feeding inside tillers.

Efficacy against Rice Leaf Folder, Cnaphalocrocis medinalis (Guenee)

All insecticidal treatments significantly reduced leaf folder (LF) damage compared to the untreated control throughout the spray schedule ( [12] reported superior control of rice leaf folder by diamide insecticides; Patel et al. (2023) [17] explained that tetraniliprole causes prolonged muscle paralysis through ryanodine receptor activation, supporting its consistent performance in the present study. Jaglan et al. (2023) [7] observed that chlorantraniliprole-based formulations were highly effective against leaf folder with lower toxicity to non-target organisms.

Efficacy against Rice Whorl Maggot, Hydrellia sasakii

All insecticidal treatments significantly reduced whorl maggot (WM) leaf damage compared to untreated control at all observation intervals ( [12] reported excellent control of rice whorl maggot by bifenthrin due to rapid knockdown effect and strong contact toxicity against adult flies and early larval stages. Singh et al. (2021) [19] also confirmed carbosulfan's effectiveness through systemic and contact action by inhibiting acetylcholinesterase activity.

Grain Yield

All insecticide-treated plots recorded significantly higher grain yield compared to the untreated control (46.00 q/ha) (Table 6). The highest grain yield was recorded in Chlorantraniliprole 18.5% SC (52.71 q/ha), followed by Bifenthrin 10% EC (51.82 q/ha) and Carbosulfan 25% EC (51.70 q/ha). The differences among treatments were statistically significant (CD = 3.20; SE(m)± = 1.04).

Economic Analysis

Economic analysis of insecticidal treatments (Table 6) revealed that Bifenthrin 10% EC recorded the highest ICBR of 3.43 with a net benefit of Rs 7,754 ha⁻¹, making it the most economically viable treatment. Carbosulfan 25% EC (ICBR: 1.90; net benefit: Rs 5,054 ha⁻¹) and Lambdacyhalothrin 5% EC (ICBR: 2.00; net benefit: Rs 2,905 ha⁻¹) provided reasonable returns. Despite recording the highest grain yield, Chlorantraniliprole 18.5% SC recorded a moderate ICBR of 1:1.60 due to its higher cost of application. Tetraniliprole 18.18% SC recorded the lowest ICBR of 1:0.74, owing to its high market price relative to yield gains. These findings are in agreement with Hegde et al. (2015) [6] , who reported higher profitability of pyrethroidbased insecticides due to their lower cost per application. Katel et al. (2023) [10] also confirmed that conventional insecticides like Lambda-cyhalothrin and Chlorpyriphos ensure reasonable economic returns, while certain newer molecules despite high efficacy may not yield favorable ICBR under field conditions (Devi et al., 2021) [3] .

Conclusion

The present investigation conclusively demonstrates that all evaluated insecticides significantly reduced infestation of yellow stem borer, gall midge, leaf folder and whorl maggot in rice compared to untreated control. Carbosulfan 25% EC and Bifenthrin 10% EC emerged as the most effective treatments against stem borer and whorl maggot, respectively, while Tetraniliprole 18.18% SC was most effective against leaf folder and Bifenthrin 10% EC against gall midge. Chlorantraniliprole 18.5% SC recorded the highest grain yield (52.71 q/ha). Economic analysis revealed Bifenthrin 10% EC as the most economically viable treatment with an ICBR of 1:3.43. Based on bio-efficacy and economic returns, Bifenthrin 10% EC @ 2.5 ml/l and Carbosulfan 25% EC @ 1.2 ml/l are recommended for inclusion in integrated pest management (IPM) programmes for rice insect pest management under Bastar Plateau conditions of Chhattisgarh.

Acknowledgement

AcknowledgmentsThe authors express their sincere gratitude to the Dean, Indira Gandhi Krishi Vishwavidyalaya and the Head, Department of Entomology, Shaheed Gundadhur College of Agriculture and Research Station for providing necessary facilities and guidance during the course of investigation. The authors are also thankful to the faculty members and staff of the Department of Entomology for their valuable support and cooperation during the experimental work conducted at the Research cum Instructional Farm, Jagdalpur during Kharif 2024. *Corresponding authors' Email: [email protected] **Department of Entomology, Shaheed Gundadhur College of Agriculture and Research Station, Jagdalpur -494005, Chhattisgarh, India.

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