Non-toxic Fungicide

Hi,

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?

Any ideas/thoughts would be greatly appreciated

Best Regards,
Steve

Hi Steve, welcome to Permies!

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.

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.

Sulfur is the best natural prevention for powdery mildew and the fungus cannot build any resistance to it, unlike other fungicides.

And of course neem oil, but it takes a lot of care to be used correctly.

Sooty mold is usually an indicator that you have sap-feeding insects of some sort on your plants. The honeydew exuded by aphids, scale, leafhoppers and other similar critters is sugary and the perfect growing medium for this type of fungus. So getting rid of the sap feeders is the best way to limit the mold, and this is why neem and soap are so effective. Soap and water also help wash off the mold and this is good for the plants, because if it's thick it blocks the light and reduces the ability of the leaves to do their job. I often just spray off as much as I can with the hose, especially with citrus trees, and that's usually all they need once or twice a year.

Steve, that recipe that you post will work.

I have a simple recipe that uses easy ingredients:

A really good treatment for powdery mildew is: 1 gal water, 1 T dish soap, 1 T baking soda.

I put it in a spray bottle to make applying it easy.

Some recipes call for adding oil. I have never found a need for the oil.

https://permies.com/t/143591/health-nearby-plants-cover-crops#1124238

Will these different recipes work against peach leaf curl?

Jon, you can use a bicarbonate antifungal on peach trees but the timing is critical. The leaf curl fungus overwinters in bark crevices and waits for wet conditions in early spring to activate. When the spores "wake up," they extend a long vesicle along the wet surface of a branch until it contacts a bud that is just starting to open. The leaf tissue in the swelling bud is vulnerable because it hasn't formed much of a cutlcle yet and this is how the fungus gets into the cellular structure of the developing leaf. Once you see the discoloration and deformed leaves the damage has been done and there's little point in trying to treat it because it's inside the plant.

So you need to do your antifungal spraying on the entire tree right before bud break, and reapply after rains or heavy dew. I prefer potassium bicarb for this purpose because I don't like loading my soil up with sodium.

Thank you Phil. I have been spraying my peach trees with a copper anti-fungal. Bicarbonate sounds cheaper. I was interested when I saw that neem oil also had anti-fungal properties.

We have had and still have a very wet spring that hardly let me spray in between. In western Oregon we have a steady misty rain that averages less than 1/3 inch a day on measurable rainfall days. I respray after every 1/2 to 1 inch of rain.

I try not to use copper-based solutions in general except as a last resort, mostly because they persist in the soil around the trees and harm all the beneficial fungi. Give the bicarbonate a try and see how you get on. We have very similar conditions in this area to western Oregon, especially in terms of spring weather often being really wet.

Non poisonous solutions to molds and rots include:

Increased airflow, for example through pruning or thinning

Increased sunlight, for example through wider spacing and less competition from shading trees

Growing varieties that are less susceptible

Growing species that are not susceptible

Planting into better draining soil, for example adding sand

Don't spray things on the trees that interfere with the plants protective endophytes

Joseph Lofthouse wrote:

Don't spray things on the trees that interfere with the plants protective endophytes

What are these types of things?

I might also ask the OP what fertilization or other inputs are being used?  

Many pests and disease outbreaks correlate with nitrogen or phosphorus fertilizer excesses that feed problematic organisms via plants, and suppress pest and disease control organisms. Aphids and many other organisms that can be problematic thrive on the nitrogen based proteins and phosphates (like ATP) that plants produce in excess when overfed. On the other side of the coin, micronutrients and calcium and magnesium are oft in deficit or imbalance due to soil biodiversity that would help chelate minerals in the soil being depressed by excessive fertilizer or biocides. Most problems relating to all of the above can be solved with biological processes, and these can be facilitated with earthworks like those outlined in keyline design, Sepp Holzer’s work, and others’. Of course its not this simple, but just meaning to point out another way to look for solutions.

Please don't take what I say too seriously here as I don't want to be the cause of any disasters but I spray my seedlings with a small, very small bit of cinnamon which helps prevent damping off, which is a fungus. I really don't know if this can be used in a similar nature here.

Otherwise, neem, baking soda, and castille soap are really all I use.

Phil Stevens wrote:Jon, you can use a bicarbonate antifungal on peach trees but ...

So, what recipe do I use, with what bicarbonate antifungal?

A couple of teaspoons of either sodium or potassium bicarbonate per litre of water (warm water helps it dissolve) and add a few drops of dish soap to act as a surfactant.