Your tree may have some Anthracnose and many people spray with copper for that.

Flies can pollinate mangoes.

Did you get any fruit developing?

no fruit yet. So just look for any insecticide or pesticide spray with coppper? You spray it on the flowers, or..?

There's been some rains here past few days, from what i read, that's how anthracnose developed?

Charles, I believe damp/dewy and or rain can cause Anthracnose, I agree with Tropicdude...sounds like that might be what you have?

Here's a video that explains the difference between Anthranose and Powdery Mildew...
Diseases of Mango Video

There's several brands out there...below is a couple of them...you might be able to find it at Home depot, WM or Lowes. Make sure you follow directions, don't add any more that what is recommended. Apply when the temps are not too hot, early or late in the day.

One of my Glenn in ground had Powdery Mildew this year and I lost a TON of flowers...very few fruits are setting :o(...so I feel your pain. Good luck!

Bonide Liquid Copper Fungicide

Here is a link that might be useful: Souther Ag: Liquid Copper Fungicide...

thanks puglvr, i just grabbed a bottle of southern ag. Did you applied the fungicide all over the mango trees including flowers and leaves, or..?

I only applied to the blooms because my leaves were fine...but if you have the symptoms on your leaves you can spray the leaves too. Make sure you don't use too much, I actually only used 3/4 of the recommended amount, since I was afraid it would be too strong? But I'm NO expert...I'm fairly inexperienced when it comes to spraying with Fungicide as well. Don't spray in the heat of the day, not sure where you live? I live in very warm FL and the sun might damage the blooms and leaves from the spray when the temps are very warm/hot. Unless you're growing them inside?Then you can spray them where there is fresh air prefably outside in the shade and let them DRY completely. Good luck and hope it works! I think it was too late for my Glenn since most of the blooms didn't make it :o(