Environmental and Application Factors Associated with Bacillus-Based Control of Soilborne Crop Diseases

Abstract

Soilborne diseases damage crop roots and reduce harvests across many farming systems. Bacillus treatments can reduce these losses, although their performance changes between experiments and farms. This paper examines environmental and application factors using published experiments and publicly accessible research records. The evidence covers fungal, oomycete, and bacterial diseases affecting vegetables, beans, and sugar beet. Reported treatment means were extracted without inventing observations or combining incompatible disease scales. Temperature, soil water, acidity, organic inputs, root colonization, formulation, dose, and application timing were examined. Within individual studies, stronger protection often followed suitable root placement and supportive carrier materials. One cucumber experiment reported disease incidences of 75%, 50%, and 25% for control, 1%, and 2% fertilizer treatments. Another experiment increased control efficacy from 53.6% to 72.2% through combined application methods. However, Bacillus subtilis MBI 600 failed against Pythium despite persisting mainly as spores. Field evidence also showed that benefits depended on disease pressure, treatment schedules, and strain combinations. Several experiments linked protection with root biofilms, antimicrobial compounds, or changes in plant defense. These findings support matching each strain and formulation with its intended crop, pathogen, and soil conditions. They do not establish one temperature, acidity level, or dose suitable for every Bacillus product. Better trials should measure viable cells, root establishment, environmental conditions, disease development, and marketable yield together. Such measurements would make practical recommendations more reliable and easier to compare.