Reading from Veronica Read's book Hippeastrum, Red blotch or red spot is a fungal infection. Spots enlarge into cankers with red borders and brown center. The scapes weaken and can snap. There can also be a distortion of the leaves and the scales around the neck. It's considered to be an environmental issue, crowded bulbs, high humidity, too much splashing water on the neck. Read saids to treat it with a systemic fungicide, which you can buy at a garden store. You can dust with powdered sulfur or cinnamon. Also reduce moisture and improve airflow around the bulbs. It is mostly cosmetic, and normally doesn't kill the bulb. I get it at the end of every summer in some of my bulbs, because they are tightly packed into pots, and get a lot of rain and humidity outside in Florida. I doubt if you can ever eliminate it totally from an infected bulb and it will spread by spores. It depends on your tolerance of disease as to how much you want to put into treating an individual bulb. If you see it on a newly purchased bulb, I wouldn't try to save it past the initial blooming.
