Q.Black spot on mandevilla plant
It is starting to look pretty sick. I am loosing leaves fast and not sure if I can save it
Your Mandevilla could have a touch of sooty mold, pests, bacterial leaf spot or any number of other common diseases, and the corrective action depends on which one it is. These articles will help you narrow down what's causing the black spots and provide tips on how to nurse your Mandevilla back to health:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-pest-problems.htm
https://www.gardeningknowhow.com/plant-problems/disease/
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm