Just shake the bottle up and spray all of the plants' leaves and soil surface, especially where the fungus is growing on the perlite. Follow the directions on the bottle about washing your hands and not breathing it. Only apply as often as directed or less. When the fungus is dead, you probably wont need it for a good long while.

I wouldn't reccomend Neem Oil. There's a Texas A and M study you can read on the web that reviews its effectiveness as a miticide. The study found that as a side effect severely stunts the plant's growth by inhibiting foliar gas exchange.

Also, my extension agent who is very knowledgable about Neem Oil said that it is not effective as a fungicide (contrary to the label).

Thanks for the heads up joshlynch. It has not seemed to have affected my plants, but it sure killed off all the yellow fungus. I believe the research stated that four times the recomended dosage of neem oil was used on the plants in the study and that those plants were of a particular species, not a variety of species. In limited use and of more reasonable dosage, neem oil probably would not be harmful to anything other than insects and fungus. If in doubt, one can always try the more toxic chemicals or use sulfur based products.

ive have been using it for the days and the yellow mold still continues to grow, ive even cahnged soils and it's still growing