Answer: Let's go over the cultural requirements of Mandevilla (Dipladenia) and make sure everything was on track. They like the temperature on the warm side (minimum of 55F in winter). Bright light to semi-shade is the lighting you are looking for, never direct sun. Water mandevilla regularly from spring to autumn, sparingly in the winter. Mandevilla likes a bit of humidity during periods when the plant is in bud or in flower. Are we together? Does it sound like your environment/practices? If not, youshould probably adjust accordingly if you decide to try again. Gray mold is prevalent in areas where the growing conditions are cool, humid and still. Try to prevent it from re-occurring by increasing air circulation (without placing the plant in a drafty area), reducing watering/misting and maybe moving to a warmer spot. When gray mold attacks, be sure to remove and destroy infected leaves. You may also want to try spraying with a fungicide; follow label directions carefully.
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