Integrated Management of White Rust (Albugo candida) in Indian Mustard Using Biocontrol Agents under Field Conditions

White rust of Indian mustard (Brassica juncea L.), caused by the obligate oomycete Albugo candida (Pers.) Kuntze, represents one of the most economically devastating biotic constraints to mustard cultivation across diverse agro-climatic regions of India. The disease is particularly severe during the Rabi (winter) cropping season, when cool temperatures and high relative humidity create ideal conditions for pathogen proliferation and disease development. The present field investigation was systematically conducted during the Rabi season of 2024-25 at the Agricultural Research Farm of Vikrant University, Gwalior, Madhya Pradesh, with the twin objectives of evaluating the efficacy of selected biocontrol agents under field conditions and analyzing disease severity trends across major mustard-growing agro-climatic zones of India. The experiment was designed following a randomized block design (RBD) with four replications and seven distinct treatment combinations comprising Trichoderma viride, Pseudomonas fluorescens, their synergistic combination, botanical resistance inducers (garlic extract and salicylic acid), a fungicide standard (Mancozeb 75% WP), and an untreated control. Critical parameters including disease incidence (%), percent disease index (PDI), and seed yield (kg ha⁻¹) were recorded at weekly intervals across the entire crop growth period from November 2024 to February 2025. Experimental results demonstrated that the combined application of Trichoderma viride and Pseudomonas fluorescens was significantly superior among all biocontrol treatments, reducing disease incidence to 22.1% and PDI to 26.7%, representing a 52.9% disease reduction over the untreated control. This treatment also produced the highest seed yield among biocontrol options at 1580 kg ha⁻¹, reflecting a 54.9% yield advantage over the control (1020 kg ha⁻¹). The chemical fungicide Mancozeb 75% WP outperformed all other treatments with a PDI of 23.4% and maximum yield of 1650 kg ha⁻¹, serving as an effective benchmark. Regional analysis confirmed higher disease pressure in eastern and north-eastern India due to elevated humidity and temperature fluctuations. The study strongly advocates for the integration of biocontrol agents into sustainable, eco-friendly integrated disease management (IDM) programmes for mustard production systems in India.