S. Harish

Beyond synergy: Integration of entomopathogenic fungi and botanicals as eco-friendly solutions for sustainable pest management

The widespread use of synthetic pesticides in contemporary pest management has been a double-edged sword, while they initially providing effective control of pest populations, their extensive use has ultimately contributed to the emergence of pesticide-resistant pests, accelerating biodiversity loss and environmental polluting by hazardous chemicals. As a result, the development of sustainable alternatives for pest control, including entomopathogenic fungi (EPF) and botanical-derived insecticidal agents, is emerging. Despite their potential, critical limitations inherent to EPF include a slow rate of action and acute sensitivity to abiotic factors, which necessitate synergistic integration with rapid-action botanicals. This paper aims to review combinatorial strategies, that leverage independent yet complementary modes of action, not only preventing the evolution of resistance but also increasing mortality, yielding significantly lower median lethal concentration (LC50) and median lethal time (LT50) values than those obtained with single agent treatments. The reduced doses required for both components improve their suitability for organic agriculture and integrated pest management (IPM) programmes, where minimising pesticide residues is a priority. This review synthesises the current literature and incorporates meta-analysis to discuss how botanicals enhance EPF performance by interfering with insect cuticular defences, altering cuticular permeability, modulating host behaviour and providing protection against ultraviolet radiation and temperature stress. We identified the key issues and areas for improvement in these integration strategies and proposed future directions focusing on compatibility optimisation, advanced formulations and predictive models for sustainable pest management.

Genomic insights and pathogenic potential of begomovirus infecting bitter gourd (Momordica charantia L.) in Tamil nadu, India

Morphological and molecular diversity of Alternaria porri isolates causing purple blotch disease in small onion across Tamil Nadu

Purple blotch caused by Alternaria porri is one of the most destructive diseases limiting small onion (Allium cepa L.) production in Tamil Nadu. To understand the prevalence and variability of the pathogen, a comprehensive survey was conducted during 2024 across major onion-growing regions of the state. Disease severity varied considerably among locations, with percent disease index (PDI) values ranging from 9.80–76.80 %, indicating the widespread occurrence of the disease under diverse agro-climatic conditions. A total of 31 isolates of A. porri were recovered from infected onion samples and characterised using cultural, morphological and molecular approaches. The isolates exhibited marked variability in colony characteristics, sporulation, conidial morphology and virulence, suggesting the existence of diverse pathogen populations within the state. Pathogenicity studies identified several highly virulent isolates capable of causing severe disease symptoms. Molecular characterisation based on internal transcribed spacer (ITS) sequencing confirmed the identity of the isolates, showing 90–100 % similarity with reference A. porri sequences available in the National Center for Biotechnology Information (NCBI) database. Species identity was further validated using Alt a1 gene-specific primers. Phylogenetic analysis revealed moderate genetic diversity among the isolates and grouped them into distinct clusters, reflecting their evolutionary relationships. The study highlights the substantial spatial, morphological and molecular variability present in A. porri populations associated with onion purple blotch in Tamil Nadu and provides valuable baseline information for disease surveillance, resistance screening and the development of effective management strategies.