Studies on the efficacy of some entomopathogenic fungi against sucking pest of rice

Introduction

Rice (Oryza sativa L) is one of the most important cereal crop and staple food for about half of the world's population. Rice belongs to the family Poaceae. Rice dominates Indian agriculture and accounts for 40 per cent production under food grains. From transplanting to maturity, the rice crop also needs warm, humid weather, which is ideal for the growth of insect pests. Only 23 of the over 300 insect pest species that have been identified in rice crops are known to inflict financial harm. In India cultivation of rice is mainly practiced in Uttar Pradesh, West Bengal, Andhra Pradesh, Chhattisgarh and Bihar. Bihar ranks fifth in the cultivation of rice (3268 tone ha). A number of insect pests that attack rice plants account for yield losses of 24% worldwide. Insect pest causes at least 20% field losses in rice in India. At least 20 of the more than 70 insect pest species that are known to feed on rice have the potential to significantly reduce rice output. Pest outbreaks can be caused by a number of factors, including climatic conditions, inadequate irrigation, high nitrogen fertilizer application rates, and excessive pesticide usage. Insect pests attack all parts of the rice plant at all growth stages and some serve as vectors of viruses that adversely affect the plant. (Pathak et al., 1982) [8] . Over 100 species of insect's attack and damage rice. Many of them often appear sporadically but do not cause economic loss. The main pests of economic significance in India are the stem borers (Scirpophaga incertulas), gall midge (Orseolia oryzae), brown planthopper (Nilaparvata lugens Stal), leaf folder (Cnaphalocrocis medinalis), and green leafhopper (Nephotettix virescens). These pests frequently cause production constraints in a variety of rice-growing environments. Leptocorisa oratorius (Fabricius), L. acuta (Thunberg), and L. chinensis (Dallas) are the three most prevalent seed-feeding bugs of rice (Oryza sativa Linnaeus) in Asia. The rice earhead bugs, both nymphs and adults, cause damage by feeding on the sap of milky grain and turning them chaffy. The management of earhead bugs (Leptocorisa spp.) as rice pests primarily involves the use of chemical insecticides. With public concern over the use of chemicals in agriculture and their impact on the environment continuing to mount, safer approaches like biological control are gaining greater significance. A number of natural enemies have been evaluated against rice bugs. Among these, the entomopathogenic fungi, particularly Beauveria bassiana, Metarhizium anisopliae, and Lecanicillium sasknae, are the most important. Entomopathogenic fungi (EPF) are fungal species that are pathogenic to insects. These fungal pathogens play a vital role in insect population dynamics, making them the earliest insect pest control agents. Earliest farmers relied on the actions of predators, pathogens, and host plant resistance for the control of insect pests until the discovery of insecticides, The brown planthopper (BPH), Nilaparvata lugens Stål, is a major sap-sucking pest of rice, Oryza sativa L., inducing symptoms commonly referred to as hopper burn and causing substantial yield loss in most rice-producing countries. Heretofore, neither was the biology or ecology clearly understood, nor was there an effective method of controlling this sucking pest other than using chemicals.

Materials and Methods

Methodology

The field trial was taking place at IGKV Raipur's research farm during the Kharif 2023 season. It was used a random block design with five treatments: three entomopathogenic fungi Lecanicillium saksnae (1x10 8 spores/gm), Beauveria bassiana (1x10 8 spores/gm), Metarhizium anisopliae (1x10 8 spores/gm), one standard check insecticide (thiomethoxan 0.2 g/l), and an untreated control. The treatments were applied thrice at 10 days interval with knapsack sprayer using 500 Lt/ha spray fluid at panicle initiation stage that coincided with the initiation of pest infestation. The pre and post treatment count for BPH was recorded one day before and 5 and 10 days after each spray for 10 randomly selected hills in each treatment and replication. The count data obtained from this experimentation for plant feeder BPH was analysed after appropriate transformation for analysis of variance to draw the concreate conclusion.

S. No.

Treatments Dose/liter of water 1

Lecanicillium saksenae (1×10

Results and Discussion

At first spray

The observations were recorded 5 DAS and revealed that all the treatments were significantly superior to untreated control. The treatment (T 4 ) Thiamethoxam 25 WG was found to be most effective over the rest of the treatments, which recorded the lowest hopper count of 9.99 per hills, which was at par with treatment (T 3 ) Metarhizium anisopliae (1×10 8 spores/gm) 13.60 with (T 2 ) Beauvaria bassiana (1 x 10 8 spores/gm) 14.50 and treatment (1) Lecanicillium saksnae (1 × 10 8 spores/gm) 16.00 hoppers per hills, respectively. The observation recorded at 10 DAS revealed that all the treatments were significantly superior to untreated control. The treatment (T 4 ) Thiamethoxam 25 WG was found to be most effective over the rest of the treatments, which recorded the lowest hopper count of 6.12 per hill, which was followed by treatment (T 3 ) Metarhizium anisopliae (1 × 10 8 spores/gm) 9.12, with (T 2 ) Beauveria bassiana (1 x 10 8 spores/gm) 10.02 and treatment (T 1 ) Lecanicillium saksnae (1 × 10 8 spores/gm) 10.01 hoppers per hill, respectively.

At second spray

The observations were recorded 5 DAS and revealed that all the treatments were significantly superior to untreated control. The treatment (T 4 ) Thiamethoxam 25 WG was found to be most effective over the rest of the treatments, which recorded the lowest hopper count of 5.89±2.62 per hill, which was followed by treatment (T 3 ) Metarhizium anisopliae (1×10

At third spray

The observations were recorded 5 DAS and revealed that all the treatments were significantly superior to untreated control. The treatment (T 4 ) Thiamethoxam 25 WG was found to be most effective over the rest of the treatments, which recorded the lowest hopper count of 2.89 ± 1.97 per 10 hills, which was at par with treatment (T 3 ) Metarhizium anisopliae(1×10 8 spores/gm) 3.12 ± 2.03 with (T 2 ) Beauvaria bassiana (1x10 8 spores/gm) 4.23 ± 2.28 and treatment (T 1 ) Lecanicillium saksnae (1×10 8 spores/gm)7.01 ± 2.83 hoppers per 10 hills, respectively. The observations were recorded 10 DAS and revealed that all the treatments were significantly superior to the untreated control. The treatment (T 4 ) Thiamethoxam 25 WG was found to be most effective over the rest of the treatments, which recorded the lowest hopper count of 1.81±1.66 per 10 hills, which was followed by treatment (T 3 ) Metarhizium anisopliae (1×10 8 spores/gm) 2.89±2.97, and treatment (T 2 ) Beauveria bassiana (1×10 8 spores/gm) 3.42±2.10, and treatment (1) Lecanicillium saksnae (1×108 spores/gm) 5.12±2.47 hoppers per 10 hills, respectively.

Overall mean population of brown plant hopper

The overall mean population across all post-treatment observations highlighted the superior efficacy of Thiamethoxam (4.99 ± 2.44 individuals/10 hills), followed by Metarhizium anisopliae (6.92 ± 2.81), Beauveria bassiana (8.86 ± 3.14), and Lecanicillium saksenae (9.72 ± 3.27). The control averaged 18.27 ± 4.40 individuals/10 hills. Relative to the control, Thiamethoxam achieved the highest population reduction (72.68%), followed by Metarhizium anisopliae (62.12%), Beauveria bassiana (51.50%), and Lecanicillium saksenae (49.26%).

Effect on natural enemies

The combined analysis of data obtained after three sprayings, indicated that thiamethoxam 25WG was found most effective against coccinellids, as it was recorded lowest overall population (1.94 coccinellids/hill), followed by Lecanicillium saksenae (1x10 8 spores/gm) (2.26 coccinellids/hill). The next effective treatment was Beauveria bassiana (1x10 8 spores/gm) (2.27/hill) and metarhizium anisoplea (1x10 8 spores/gm) (2.30 coccinellids/hill). Lecanicillium saksenae (1x10 8 spores/gm) Beauveria bassiana (1x10 8 spores/gm) and metarhizium anisoplea (1x 10 8 spores/gm) was declared as the least effective treatment. The highest coccinellid population (2.39 coccinellids/ hill) was recorded in an untreated control.Overall mean population of spider after first, second spray and third spray: The combined analysis of data obtained after three sprayings, indicated that thiamethoxam was found most effective against spiders, as it was recorded lowest overall population (2.08 spiders/hill) and Lecanicillium saksnae (1x10 8 spore/gm)(2.23 spiders/hills), followed by metarhizium anisoplea (2.26 spiders/hill) and beauveria abssiana (2.24 spiders/hill).The highest spider population (2.32 spiders/ hill)was recorded in an untreated control. Overall mean population of spider after first, second spray and third spray: The combined analysis of data obtained after three sprayings, indicated that thiamethoxam was found most effective against rove beetle, as it was recorded lowest overall population (1.91 rove beelte/hill) and Lecanicillium saksnae (1x10 8 spore/gm)(2.27 rove beetle/hill), followed by metarhizium anisoplea (2.30 rove beetle/hill) and beauveria bassiana (2.27 rove beetle/ hill).The highest spider population (2.39 rovebeetle/hill) was recorded in an untreated control.

Yield analysis:

The data on the yield of rice that was influenced by various entomopathogen treatments are presented in Table 4.2.13. It could be seen from the data that all the entomopathogen treatments recorded higher yields than the untreated control. All the treatments gave significantly higher yields than the untreated control. The highest grain yield of rice (51.57 q/ha) was obtained in a treatment(T 4 ) Thiamethoxam with 25 WG 0.2 g/l found on par with treatment (T 3 ) Metarhizium anisopliae 1x10 8 spores/gm, and (T 2 ) Beauveria bassiana 1 x 10 8 spores/gm. The next best treatment was (T 3 ) Metarhizium anisopliae 1x10 8 spores/gm which was 49.00 q/ha grain yield of rice which is on par with treatment (T 2 ) Beauveria bassiana 1x10 8 ( 46.76q/hac) spores/gm and (T 1 ) Leacnicillium saksnae 1x10 8 ( 38.50 q/ha).This result is in consonance with Kiran and Veerana (2012) reported that Spraying of Metarhizium anisopliae @ 2.5kg/ha produced significantly higher grain yield of paddy (8060 kg/ha) over Metarhizium anisopliae@ 2 kg/ha (7643 kg/ha) Metarhizium anisoplea at 2 kg/ha (7643 kg/ha), Clothiandidin (6701 kg/ha), and control (5922 kg/ha). This was at par with Thiomethoxam (8313 kg/ha) and Imidachloraprid (7843 kg/ha). The Metarhizium anisoplea 2.5 kg/ha was not found to be phytotoxic, and it was safer for natural enemies.

Conclusion

Overall performance of various microbial treatments based on mean hopper population data revealed that, the treatment with thiamethoxam 25 WG, Metarhizium anisopliae with 1x10 8 spore/gm was the most consistently effective and significantly superior over all other fungal treatments throughout the trial followed by B. bassiana 1x10 8 spore/gm and Lecanicillium saksenae 1x10 8 spore/gm reducing the hoppers population. Metarhizium anisopliae is superior to Beauveria bassiana and Lecanicillium saksnae on 5 DAS and 10 DAS, whereas Metarhizium anisoplea recorded a 60-65 percent reduction in the survival population. The results obtained from the study clearly revealed that the efficacy of Metarhizium anisopliae, Beauveria bassiana, and Lecanicillium saksnae increased with an increase in the number of days after spray and reached the highest efficacy on 10 DAS in each spray.

Acknowledgement

I would like to thanks my deepest sense of gratitude to the Chairman of my Advisory Committee Dr. Sanjay Sharma, Principal scientist Department of Entomology, COA, Raipur (C.G.) and all the professors on my advisory committee and Dr. B. P. Katlam, Head of Department Entomology, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.) for guiding and supporting me. The Dean of COA (C.G.), Dr. H.K. Singh, Dr Vikash Singh and Dr H.K. Singh are also thanks for providing all the facilities and encouragement during present investigation. I wish to record my sincere and grateful thanks to my professor and my friends for helping me for observing BPH.

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