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Random roving survey was carried out for the incidence and relative abundance of different rice stem borers in three coastal districts viz., Vizianagaram, Srikakulam and Nellore of Andhra Pradesh, India during Kharif 2021. The damage was quantified through the dead hearts and white ears symptoms and species through a destructive sampling of the infested tillers. The survey revealed the occurrence of three different species of rice stem borers viz., Yellow stem borer (YSB), Scirpophaga incertulas (Walker), Pink stem borer (PSB), Sesamia inferens (Walker), and Gold fringed stem borer (GFSB) Chilo auricilius (Dudgeon). The damage by stem borers ranged from 10.91 to 14.70 per cent in the surveyed mandals of Srikakulam (Amadalavalasa, Srikakulam and Seethampeta), Vizianagarm (Merakamudidam, Therlam and Garividi) and Nellore (Venkatagiri, Nellore and Dakkili) districts of Andhra Pradesh. Among the stem borers, YSB was the most predominant species, with 84.26 per cent followed by GFSB with 12.41 per cent in Srikakulam and Vizianagaram districts. A high incidence of GFSB, Chilo auricilius (80 %) was noticed in Seethampeta mandal in Srikakulam district, which is a hilly area where sugarcane is grown predominantly. In Nellore district, yellow stem borer is the only species prevalent where mono-cropping and staggered planting of rice throughout the year is practiced where low PSB incidence (3.33 %) was recorded in Venkatagiri mandal of Nellore district. This study clearly brings out the variation in the abundance of rice stem borer complex prevailing in rice-based cropping systems in different districts of Andhra Pradesh. [ABSTRACT FROM AUTHOR]

The stem rot caused by Sclerotium hydrophilum and false smut caused by Ustilaginoidea virens are two of the major production constraints in rice cultivation in India and other countries. Stem rot and false smut can be effectively controlled with synthetic fungicides. However, the indiscriminate use of chemical fungicides may cause development of resistance among the pathogens. In addition to this, synthetic fungicides also exhibit harmful impacts on the environment. Exploiting microbe-based alternatives for managing plant diseases diminishes public concerns about the ill effects of pesticide usage in crops. In this regard, the present study was designed to investigate the potential of native microbial biocontrol agents (BCAs) from rice rhizosphere for the sustainable management of stem rot and false smut diseases in rice. Potential BCAs and pathogens were identified and characterized through morphological, biochemical, and sanger sequencing techniques. Bio-efficacy tests of potential BCAs against stem rot and false smut diseases on rice under glasshouse conditions indicated higher seed vigour index of the treated seeds, significant improvement in the growth of the seedling, increased dry weight, reduction in percentage disease index viz., 70.03% (stem rot) and 69.24% (false smut) over the control plants. Phytohormones indole acetic acid (IAA), abscisic acid (ABA), gibberellic acid (GA), salicylic acid (SA), and zeatin (tZ) were detected and quantified in the four potential BCAs using liquid chromatography- tandem mass spectrometry (LC-MS/MS). Scanning electron microscopy (SEM) studies revealed the endophytic nature of the strains in rice. The study indicated a positive correlation between the diversity and concentration of phytohormones released by the bioagents and enhanced plant growth promotion and disease suppression in rice., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)