I'm growing mango plants from seed and they are in either 1 gal or 3 gal containers. Almost all of them (12 pots) have either got, or have started getting, different problems. I've read other suggestions about using a copper-based spray, or various insecticides, fertilizers, but these all seem to be aimed at much larger plants. My plants are all 6 months-1 year old and are growing inside by floor to ceiling windows (next to the beach in the Los Angeles area) with a special plant light on for 4 hrs/day. The photos below show what I think are 2 different problems: powdery mildew and anthracnose. How can I control and eliminate these in young plants? My tallest plant is about 18". Thank you for any help on this -- I love these plants and don't want to lose them.
Mango Plant Disease/Pests
Certified GKH Gardening Expert
This is likely a bacterial leaf spot.
You can apply a copper fungicide.
Here are some links that will help you.