i use rubbing alcohol as a spray it kills mold, aphids ect it evaporates quickly enough so it doesn't harm the plant ...mine anyway mist it lightly , if you need you can apply again in awhile i also try and cut leaves as close to the stem as i can anytime i handle my plants i spray my hands with alcohol also you can use perxiode with your water
4 me
+1 on the isopropyl alcohol spray (just on the effected area). I’d also use cotton balls and Qtips to scrub down the area as the spores can blow around and effect other plants. Then look into a systemic drench (like Plant Doctor of Actinovate) as the Botrytis can grow within the plant and spread to other parts. (Tons of info on systemic sprays from commercial grape cultivators.)