Background: Among all the coconut pests, rhinoceros beetle causes acute and serious damage to coconut palm. Management of this pest is very difficult due to its nocturnal activity, and also, it damages the emerging leaf inside the bud. Management of rhinoceros beetle using entomopathogens will be of great importance as it is economical and ecofriendly. Studies were carried out to decipher the biocontrol potential of indigenous entomopathogenic bacterium (Bacillus thuringiensis) and entomopathogenic fungi (Metarhizium robertsii and M. majus) against Oryctes rhinoceros in the field, individually as well as in combination, by soil drench as well as by topical spray method. Results: The study showed that B. thuringiensis strain NBAIR-BTAN4 showed 24.8% mortality at 5th week in soil drench method and 24% mortality in topical spray method. M. robertsii showed 24% mortality at 5th week in soil drench method as well as topical spray method. Similarly, M. majus showed 24% mortality in soil drench method and 23.2% in topical spray method at 5th week. In combination, NBAIR-BTAN4 + M. robertsii showed 40.8 and 44% in soil drench and topical spray method at 5th week, respectively. Combination of NBAIR-BTAN4 + M. majus showed 44.8 and 40.8% in soil drench and topical spray method at 5th week, respectively. Combination of NBAIR-BTAN4 + M. robertsii + M. majus showed 52.8 and 57.6% mortality at 5th week in soil drench and topical spray method, respectively. Conclusion: The present study showed application B. thuringiensis in combination with M. robertsii and M. majus is effective in management rhinoceros beetle in coconut orchard. Study also indicated that soil drench method is more promising strategy than topical spray method in managing larval population of the beetles and also confirmed that B. thuringiensis, M. robertsii and M. majus are compatible and they seemed to have a synergistic effect in controlling the pest in coconut orchard.

A field survey was done in teak (Tectona grandis F.) forests in South India to explore the entomopathogenic effect of Metarhizium anisopliae (Ascomycota: Sordariomycetes) against teak defoliator, Hyblaea puera (Lepidoptera: Hyblaeidae). About 300 soils and infected insect samples were collected during the survey and thirty-six fungal isolates were isolated from soil and insect samples and characterized. The fungi were cultured on PDAY with dodine and antibiotics. Generally, the EPF culture was incubated at 27 °C in darkness for 15 days. Virulence of the Entomopathogenic Fungi (EPF) ability to germinate under cold and heat temperatures was assessed in a culture impregnated with conidia. In the experiment, it was found that for the first time Metarhizium quizhouense, Metarhizium robertsii, and Metarhizium majus species caused significantly higher mortality to hosts. These isolates of M. anisopliae, M. robertsii, M. majus, and M. quizhouense were all considered to be effective virulent and environmentally adaptive. The Metarhizium isolates were recommended as effective bio-control agents through the field investigation of teak defoliator Hyblaea puera from South India forest. This study paves the way to utilize the indigenous isolates of EPF for the control of teak defoliator and to combat the pests thatare resistant to insecticide.

Background: Banana fruit scarring beetle (BFSB), Basilepta subcostata (Jac.) (Chrysomelidae:Coleoptera), is an important insect pest feeds on leaf and fingers, which affects the cosmetic value of the fruit. The pest is distributed in Assam, Bihar, West Bengal, Chhattisgarh, and North-eastern Hill regions of India. Results: The pest is currently managed by foliar spray with insecticides. In order to identify eco-friendly control of the pest, attempts were made to isolate microbial agent and evaluate their potential to control the pest. A total of 27 entomopathogenic fugal isolates were obtained from Odoiporus longicollis (Oliver), Cosmopolites sordidus (Germar), Basilepta subcostata (Jac), and other insect Galleria mellonella (Fabr). Based on colony morphology, the collected fungal isolates were identified as Metarhizium spp. (17) and Beauveria spp. (10). Through ITS sequencing, the fungal isolates were further characterized at species level as B. bassiana (8), B. brongniartii (2), M. anisopliae (8), M. robertsii (6), M. guizhouense (2), and M. pinghaense (1). Their sequences were submitted in GenBank and obtained accession numbers. Among 27 isolates tested against B. subcostata under laboratory conditions, 3 isolates (M. anisopliae NRCBEPF-36, M. pinghaense NRCBEPF-7 and B. brongniartii NRCBEPF-27) recorded 100% beetle mortality, followed by 11 isolates with 95–99% and 13 isolates with 88–93% within 8 days of treatment. Conclusion: This study highlights the two native North East India isolates B. brongniartii NRCBEPF-27 (MT151781) and M. anisopliae NRCBEPF-36 (MT140308) showed the significance to use as potential biocontrol agents against banana fruit scarring beetle B. subcostata. Further experiments under field conditions are required to evaluate their biological control efficacy against the pest.

Background: Thirty-six entomopathogenic fungi (EPF) were isolated from soil and insect cadaver samples, collected from different forest types, viz., wet evergreen, moist deciduous, dry deciduous and scrub type in South India. Partial sequences of two parsimony informative genes ITS and RPB1 were determined under a phylogenetic approach for assessing the genetic diversity. Results: Twenty-seven RPB1 gene sequences and 34 sequences of ITS1, 5.8S and ITS2 regions belonging to 36 EPF were analysed for identification and characterization. Four species of Metarhizium viz., M. anisopliae, M. roberstii, M. majus and M. guizhouense were differentiated. The isolates could be grouped into four main clades of 1–5. Most of the fungi appeared to be closely related to M. anisopliae. Based on the colony characters, colour, conidial size and shape, 27 isolates were morphologically identified as M. anisopliae. Seven strains were apparently related to M. robertsii, three isolates were similar to M. majus and the remaining one was identified as M. guizhouense. Morphological studies in congruence with phylogenetic analysis resolved the species diversity. Bioassay studies showed that M. quizhouense, M. majus and M. robertsii were effective against the banana stem weevil Odoiporus longicollis. Conclusions: This is the first attempt to study the diversity and occurrence of Metarhizium species in forests of South India. Wet evergreen forest of Aralam in South India was rich in EPF diversity particularly for three species namely, M. quizhouense, M. robertsii and M. anisopliae.

Background: The banana stem weevil,Odoiporus longicollis(Olivier), is a serious threat to banana cultivation world over. Since banana is a food crop, the use of naturally infecting biological control agents could be an effective alternative to manage the insect pest instead of harmful chemicals. Also, the efficacy of entomopathogenic fungi againstO. longicolliswas used in bioassay.Results: Among theBeauveria bassianaisolates tested the median lethal concentration (LC₅₀) 10.468 × 10⁵conidia ml⁻¹when treated withB. bassiana(NRCBEFPMP1), two other isolates ofB. bassiana, namely NRCBEPF22 and NRCBEPF2, were also effective againstO. longicollisand recorded LC₅₀of 12.617 × 10⁵and 12.891 × 10⁵conidia ml⁻¹, respectively. The results of bioassay with differentMetarhiziumspp. showed variations in efficacy, where the most virulent isolate wasM. quizhouense(NRCBEPF11) with LC₅₀8.050 × 10⁵conidia ml⁻¹. Scanning electron microscopic analysis showed thatB. bassianaandM. quizhouensecaused infection by cuticle penetration and completed the infection process in 15 days. The composition of volatile organic compounds released byB. bassianaandM. anisopliaeduring pathogenesis showed that a significantly high number of known insect volatiles were present in infected insects. Consequently, these volatiles were emission in Insect attractant, Odorant receptor agonist, Plant hormone Plant, and Microbial Metabolites, through the biological activity, such as Methyl salicylate, Benzaldehyde, alpha-Terpineol, Limonene, Benzene, 1,2-dimethoxy, Phthalic acid, 1-Octadecene, Phenylacetaldehyde, 3-Octanone, Octanal, Methylheptenone and 2-Ethyl-1-hexyl alcohol.Conclusion: Overall, the results show that EPF could significantly reduce damage byO. longicollisand produce a wide profile of secondary metabolites. Further, analysis was used for principal components to determine whether separated classes of fungi can be distinguished from one another based on their metabolite profiles.