We investigated the possibility to reduce the usage of Blasin®Flowable (BF), a disinfectant inhibiting the germination and appressorium formation of Pyricularia oryzae Cavara conidia, by using carbon dioxide microbubbles (CO₂MB).  Germination was significantly inhibited by 10 000-fold diluted BF solution containing CO₂MB generated by the decompression-type generator compared to CO₂ millibubbles (CO₂MMB) and CO₂MB generated by the gas-water circulating-type generator.  Appressorium formation in the 10 000-fold diluted BF solution containing both CO₂MBs was less than that in CO₂MMB.  Scanning electron microscopy showed wrinkles and dents on the surface of conidia treated with 5 000-fold diluted BF solution containing both CO₂MBs.  Via transmission electron microscopy, we observed the expansion of the vacuole and the intracellular space and bloated or absent lipid granules in the conidia treated with BF solution containing both CO₂MBs.  Our results show that inhibition of the conidium germination and appressorium formation of P. oryzae Cavara by 10 000-fold diluted BF solution could be achieved by using the decompression-type CO₂MB.