Informatics Publishing Limited

V. Ambethgar ¹, M. Swamiappan ², R. J. Rabindra ³, R. Rabindran ²

Affiliations
1 Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam 606001, Tamil Nadu, IN
2 Centre for Plant Protection Studies, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, IN
3 National Bureau of Agriculturally Important Insects, Post Bag No. 2491, H. A. Farm Post, Hebbal, Bellary Road, Bangalore 560024, Karnataka, IN

Abstract

The toxic effect of 10 fungicides on mycelial growth of Beauveria bassiana (isolate BbCm KKL 1100), a pathogen of rice leaf folders, was evaluated in vitro at three concentrations each: the normal field application rate (I.0X), 10-fold lower rate (0.1X) and 10-fold higher rate (10.0X) on agar plates. The fungicides tested were antagonistic to B. bassiana and inhibited the mycelial growth of either partially or completely depending on the concentration. At 10-fold higher concentration, all 10 fungicides caused total inhibition of mycelial growth. Two fungicides, viz., benomyl and hexaconazole, caused total inhibition of the fungus in all the three concentrations tested. Three fungicides viz., edifenphos, iprobenphos and mancozeb, appeared to be fungistatic at normal field dose (1.0X). Benomyl, carbendazim, hexaconazole, propiconazole and tricyclazole caused total inhibition of mycelial growth at 1.0X, while chlorothalonil, copper oxychloride and edifenphos were comparatively less toxic to B. bassiana causing 63.0, 72.6 and 76.3 per cent mycelial inhibition, respectively at 0.1X.

Keywords

Beauveria bassiana, Fungicides, Mycelial Growth, Rice Leaf Folders.

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V. Ambethgar ¹, M. Swamiappan ², R. J. Rabindra ³, R. Rabindran ²

Affiliations
1 Regional Research Station, TNAU, Vridhachalam 606001, Tamil Nadu, IN
2 Center for Plant Protection Studies, TNAU, Coimbatore 641003, Tamil Nadu, IN
3 Biological Control, ICAR, Bangalore 560024, Karnataka, IN

Abstract

Compatibility of Beauveria bassiana (Balsamo) Vuillemin (isolate BbCm KKL 1100) with twelve insecticides and three neem formulations was examined on agar plate to develop suitable combinations for the management of insect pests in rice fields. All chemical and botanical insecticides inhibited mycelial growth of B. bassiana either partially or completely depending on their concentrations (10X, 1X and 0.1X, where X = treated concentration). Chemical insecticides completely inhibited the mycelial growth of B. bassiana, while the neem formulations inhibited 70-86% biomass production of the fungus at 10X concentration. At 1X concentration, carbofuran caused total inhibition, but all other insecticides caused 47.4-75.5% inhibition. However, at 0.1X concentration, only neem seed kernel extract, chlorpyriphos and dimethoate exhibited 22.2%, 27.3% and 32.6% mycelial inhibition, respectively, and these could be used with B. bassiana in the field condition.

Keywords

Beauveria bassiana, Compatibility, Insecticides, Neem Products and Rice Pests.

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V. Ambethgar ¹, M. Swamiappan ², R. J. Rabindra ³, R. Rabindran ⁴

Affiliations
1 Regional Research Station, TNAU, Vridhachalam - 606001, Tamil Nadu, IN
2 Agriculture College and Research Institute, TNAU, Madurai - 625104, Tamil Nadu, IN
3 Project Directorate of Biological Control, Bangalore- 560024, Karnataka, IN
4 Centre for Plant Protection Studies, TNAU, Coimbatore - 641003, Tamil Nadu, IN

Abstract

The pathogenicity of 42 local isolates of entomopathogenic fungi including Beauveria bassiaua (22), Metarlizium anisopliae (three), M. flavoriride (one), Nomuraea rileyi (four), Paecilomyces sp. (one), Aspergillus spp. (five), Fusarium spp. (three), Zoophthora radiants (two) and Entomoplithora sp. (one) originating from a range of insect species were evaluated against third instar larvae of Cnaphalocrocis medinalis. All the isolates tested were pathogenic to the pest at varying degrees. In single-dose (1 × 10⁷conidia/ml) time-mortality assay, only five isolates of B. bassiaua, viz., BbCm KKL 1100, BbCm TVR 0101, BbCm ADT 0101 (isolated from C. medinalis), BbMp KKL 1195 (isolated from Marasmia partialis) and BbOn KKL 0597 (isolated from Oxya nitidnla), were superior to all other isolates with BbCm KKL 1100 having the lowest LT₅₀ value of 7.81days. In the multiple dose assays (ranging from 1 × 10⁴ to 1 × 10⁹ conidia/ml), the Karaikal isolate of B. bassiaua (BbCm KKL 1100 isolated from C. medinalis) was found to be the most virulent. The LC₅₀ value estimated at 13 days post-inoculation from three independent bioassays for this isolate was 2.8 × 10³ conidia/ml. This was closely followed by BbOn KKL 0597 (isolated from Oxya uitidula) with a LC₅₀ of 2.2 × 10⁴ conidia/ml. Based on the time-dose mortality factor, the B. bassiaua isolate BbCm KKL 1100 has been selected as a potential microbial agent for further investigations in field conditions.

Keywords

Cnaphalocrocis medinalis, Entomopathogenic Fungi, Pathogenicity.

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V. R. Saminathan ¹, C. A. Mahalingami ¹, V. Ambethgar ¹

Affiliations
1 Regional Research Station, Tamil Nadu Agricultural University Vridhachalam 606001, Tamil Nadu, IN

Abstract

The relative susceptibility of different life stages viz, egg, larvae and pupae of the cashew stem and ischolar_main borer, Plocaederus ferrugineus Linnaeus (Coleoptera: Ceramhycidae) to three entomopathogenic fungi (Beauveria bassiana (Balsamo) Vuillemin, Beauveria brongniartii (Sacc.) Patch (Hyphomycetes: Moniliales) and Metarhizium anisopliae (Metsch.) Sorokin I (Deuteromycotina: Moniliales) was evaluated in laboratory by topical application of conidial suspension of 107 conidial mi. Of them, M. anisopliae was found to be more effective with 36.0, and 33.3 per cent egg and larval mortality followed by B. basriana with 30.0 and 30.9 per cent egg and larval mortality, respectively. Pupal mortality was 10.00 and 8.00 per cent with B. bassiana and 111. anisopliae. There was moderate increase in terms of larval mortality due to fungal pathogens with a decrease in larval age.

Keywords

Cashew, Entomopathogenic Fungi, Plocaederus ferruginus, Virulence.

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