MPK Mono-Potassium Phosphate 0-52-34. Not a ton of info out there about it, but I have read that it is used to control powdery mildew and obviously for foliar feeding. I mix a very small amount (less than 1 tbsp per 3 gallons) in with my foliar sprays - no way to physically observe what, if any, effect it actually has. I guess I'll find out if the whole family starts glowing after mango season this year.