So I have an mango tree that has black spots on the leafs over my orchids. And it seems to be spreading to my orchids. I can't cut the tree because my late grand mother planted it for me. I have removed most of the infected branches. How often do you spray the orchids? Ive already done a test spray with a more watered down dosage and fortunately It didn't harm any of my orchids. I just don't want to over do. Seems to be a lot of mixed answers all over the web. How often do I spray the tree?
I can't help you with how often to spray but I can tell you using a fungicide at less than the recommended dosage will make whatever fungus you have build up a resistance to that formula.
The same advice is for insecticides. When you use any product, use the recommended dosage or you will end up with bigger problems of the bug getting resistant.
Use Captan if it is a fungus. This is what we use with our peach, plum and other fruit trees to prevent and combat fungus attacks. It should knock it out.
I would avoid Phyton 27. For one, it is not usable on any food crop, so you'll basically be ruining the mango.
Second, many plants simply don't take well to it. Copper is a phytotoxin, but in low doses, may be tolerated by some - not all - plants. Personally, I avoid it.