Phyllosphere Arthropods Facilitate Secondary Dispersal of Putative Mycoparasite Simplicillium: A Potential Biocontrol Strategy for Soybean Rust

Soybean rust, caused by <i>Phakopsora pachyrhizi</i>, is a major foliar disease that often escapes fungicide control, necessitating alternative strategies. We investigated whether phyllosphere arthropods, such as mites and thrips, facilitate the secondary dispersal of the mycoparasitic fungus <i>Simplicillium</i> under controlled conditions. Detached soybean leaves inoculated with <i>P. pachyrhizi</i> were subjected to either arthropod-exposed or arthropod-excluded treatments. <i>Simplicillium</i> isolates were significantly more abundant in the presence of arthropods. Molecular identification revealed identical ITS genotypes of <i>S. lamellicola</i> from both infected pustules and thrips, indicating vector-mediated fungal transmission. While some <i>Simplicillium</i> strains persisted epiphytically without vectors, their spread was minimal. These results highlight a promising approach to enhance the effectiveness of <i>Simplicillium</i>-based biocontrol through natural arthropod-mediated dissemination, warranting field validation of this self-disseminating strategy.