Mango fungus on flowers

[BluePalm]

For the past 3 growing seasons the flowers on our mango trees are being attacked by a fast-spreading fungus...before fruit set. Last year it kept our Alphonso from bearing fruit. Spraying the flowers with a fungicide is quite effective. However, we have some larger trees that are really hard to fully spray (with 100% coverage). Has anyone had any experience with this specific fungus? 
Thanks,
BluePalm