My macadamia nut tree has fungus on most of the leaves and has dropped a lot of leaves.
I've also got a sooty mold problem on my citrus trees.
Searching the web for a non toxic solution has suggested using a baking soda & neem oil solution for the fungus; and using a neem oil solution for the sooty mold.
For simplicity I plan to use the same solution for both:
Fungicide recipe per quart / litre of water:
1.5 TBLS / 22mL baking soda
1.0 TBLS / 15mL neem oil
2.0 TBLS / 30mL castile soap (emulsifier for oil/water)
3-6 TBLS / 45-90mL of neem oil per 1000 sq ft of orchard
I found one site that indicated I could use a garden hose sprayer to easily access the whole tree.
Has anyone ever used this type of recipe for a fungicide?
Has anyone ever used a garden hose sprayer to apply a fungicide?
I think you're on the right track with the neem oil as a non-toxic fungal & mold control for your trees. I've used neem on my fruit trees, and mine are of a small size so I've mixed neem oil with castile soap and applied it with a pump sprayer. I like to think that a garden hose sprayer would work, but I'm thinking of how the soap/oil would behave mixed together in their undiluted form before being mixed with water. I also wonder if there is sufficient blending of the soap/oil with the water before it flies out the end. Just for a reference, when I mix mine in a pump sprayer I prefer to add the soap to water first, then the oil. I tried the other way around once and I noticed the neem oil stayed on the surface, unmixed, coating the inside walls of the sprayer and after adding the soap it really didn't seem to mix in as well in my opinion. I also periodically shake the pump sprayer to help keep things mixed while spraying.
"Study books and observe nature; if they do not agree, throw away the books." ~ William A. Albrecht
A lot of the things that you named are better suited to prevention in my experience. You might want to explore biological controls. I have heard good things about a company called Microbe Lift or Microbe Life being used to help citrus in Florida. Another technique I've used on annuals with surface molds like powdery mildew is using potassium bicarbonate (typically sold as a natural pH adjuster) to create a spray with a pH close to 10.