Antagonistic Bacteria Bacillus subtilis Formulation as Biopesticide to Control Corn Downy Mildew caused by Peronosclerospora philippinensis

<p class='Abstract'>Downy mildew (DM) is a major disease of corn that can limit production. An alternative method of control that is currently being developed is the use of biopesticides which can inhibit the development of DM. Therefore, this study aims to test the effectiveness of <em>B. subtilis</em> antagonistic bacteria formulation in suppressing DM through seed treatment and foliar spraying. The study was carried out from June to October 2019 at Maros Experimental Farm of the Indonesian Cereals Research Institute. The first application was done by treating the seeds with the bacterial formulation with a dose of 8 g/kg of seeds. The second application was done at 16 DAP at a dose of 3 g/L. Spraying was done evenly throughout the leaves of the test plant. Observations made include incidents of downy mildew, presence of mycelium lignification, leaf chlorophyll content, stomatal density, plant height, and crop yield. Furthermore, the results showed that the application of the formula <em>B. subtilis</em> with seed treatment and spraying effectively suppressed the development of downy mildew and improved corn plants' growth. The test also showed that mycelium lignification occurred in the treatment using the formula <em>B. subtilis</em>. The treatment of B<em>. subtilis</em> tended to have higher leaf chlorophyll content in corn plants compared to control treatments. Considering the results, the Bima-15 and Perkasa variety have a relatively better response to <em>B. subtilis</em> biopesticides in inhibiting downy mildew infections, improving maize production.