How exactly does it work?
Uuum, because it does?
Not good enough, huh? Well, from what I could find it's due to a naturally occuring enzyme called Lactoperoxidase that's found in saliva, tears and milk. The Lactoperoxidase acts on a number of organisms including fungi. I don't believe it to be selective or at least couldn't find any information relative to that train of thought.
As for how it works; the best I could find was a study done on bacteria; "The action of lactoperoxidase against bacteria is reported to be caused by sulfydryl (-SH) oxidation ( Aune and Thomas, 1978); Ekstrand, et.al., 1985) The oxidation of -SH groups in the bacterial cytoplasmic membrane results in loss of the ability to transport glucose and also in leaking of potassium ions, amino acids and peptides."
It's all Greek to me, but the search prompted by your question did raise my awareness of the fact that it's non-selective of what it kills. I'm sure there are some organisms that are resistant to its effects but I'd have to guess that further studies have yet to be done.
Milk serves as food for lactobacilli which probably serve as competition for pathogenic fungi. I think this may mimic the probiotic effect of lactobacilli in the human body in keeping in check digestive tract pathogens and vaginal candida.
That said, I have tried milk on dollar spot and powdery mildew on my lawn--didn't seem to have any beneficial results. Maybe it would best be suited as a prophylactic against disease instead of a cure?
No effect on Dollar spot on my lawn either.
Reading up on Dollar Spot I found out commercial fungicides don't work well either, but extra Nitro was suggested. I put another layer of Soybean meal down, and covered the troubled spots with composted cow manure. That took care of it.
It is good to read the negative results on milk. Can you folks please describe how you mixed it and how often you sprayed? I consider milk to be experimental but initial experiments were "successful." There's no good database on milk, so let's get one started.
I can say that I have watered African violets with milk water and never once encountered any of the fungal disease or leaf drop that the AV enthusiasts told me I would. I used the same Wal-Mart soil all the way through to the eventual demise of the plants (these plants are my hotel hobby for when I'm away on business for 6 months. When I'm home I take horrible care of them. Most are dead now). I had a great experience recovering an AV my wife was growing. She's not organic and had been using Peter's 20-20-20 on it. One week it was waterlogged and looked poorly. Two weeks later she finally allowed me to take over. I put milk on it and the milk coagulated!!! I put milk on it until it stopped coagulating and poured through milky. Two weeks later the soil had a thick covering of fuzzy fungus. I milked it again and two weeks later you would never know it had had problems. The soil smelled like a forest floor and everything seemed to be fine. The AV professionals would have tossed the plant at the first sign of problems.
My thoughts on why milk works is that they provide a source of protein for the beneficial microbes that live on the plant surface. Once the beneficials are well fed, they interact with the plant to develop a stronger self protection system. It has been pretty well proved around the world that certain gasses (notably salicylic acid (oil of wintergreen) and gibberilic acid) stimulate certain genes in plants to enhance their protection system. I think milk does it differently but does the same thing.
For me: I put 1 gallon of homogenized milk diluted to close to 5 gallons in my backpack sprayer. I sprayed dollar spot areas and powdery mildew areas affecting the lawn in the fall. I also sprayed some powdery mildew on my phlox plants that always seem to get it. I did that once a week for a total of 3 doses. Dollar spot areas got worse and some areas coallesced into small dead spots (reseeded in the spring). There was no change in powdery mildew--but the plants never seem to die because of it; it's more of a nuisance.
In past years, I had also tried Scott's Lawn fungicide and did not get any beneficial results either.
Last year, I tried 3 applications of cracked corn during the spring and summer (because it was so very wet) and for the first time ever, I never saw ANY dollar spot at all last fall.
I can't remember the exact ratio that I applied milk, although I remember looking it up in this forum. Perhaps if I had used the milk regularly before the Dollar Spot outbreak, results may have been different.
Many people in my neighborhood were affected by Dollar Spot last year because of the weather conditions (continuous high humidity with warm nights, dew in the morning, and days not too hot - less that 85). Some neighbors tried commercial fungicides, some nothing, and myself organic.
I'm not sure I agree with the lactobacilli theory. It sounds good but I can't find any supporting research anywhere. There is proof regarding its role as improving the immune system in infants, but lactobacilli is an anaerobic bacteria. Wouldn't conditions need to be appropriate to support anaerobic bacteria? Are conditions appropriate on the surface of leaves? It just doesn't add up in my mind.
On the other hand, there are multiple articles regarding the role lactoperoxidase and other peroxidase based enzymes play as an anti-bacterial and fungal inoculant. There are even patents on a synthetic form used for an all purpose sanitizer to replace other harmful chemical sanitizers. Wouldn't it make more sense that this enzyme; which is naturally occuring in milk (any lactobacilli present would be killed during pasteurization, enzymes would remain) and is not only proven but also being marketed as a general anti-everything; would be the main ingredient in the ability of milk to control any disease (and/or beneficial) organisms found on leaf surfaces and in the soil?
On another note, it's also being researched and marketed for the very purpose that we're using it for; in agriculture. The product being marketed for agriculture use is the pure enzyme and I'm not sure to what extent the enzyme is concentrated in milk.
I need more time to pull the links together and want to do more research but I think (and I'm not saying it's a fact) that the use of milk as a fungicide may be an all purpose fungicide and not neccessarily healthy for our beneficial organisms. While it's the only organic means available that's shown any effect against red-thread I'm wondering if it should be used sparingly but in high concentration.
There are plenty of agricultural products designed to enhance or inoculate beneficial microbes (including lactobacilli) onto soil, turf, crops. Lactobacilli are found in the soil. No doubt milk (commonly available) is pasteurized which is why I speculate that the milk serves mainly as food for the beneficial microbes. I guess if you wanted a microbial tea, you could mix in some yogurt and let the milk sit for a bit before application.
If milk has intrinsic properties that help to suppress disease, even better. This is certainly an area I hope we find more info about over time.
Here is a link that might be useful: Example of microbe concentrate
I'm not so sure about the microbe concentrate either. I can yield the same if not better microbes from a batch of ACT. Not to say that the microbes in that product aren't good for the soil, but it smells like anaerobic to me.
I'm not trying to debate you subywu so don't take me wrong! : ) I'm just saying that what that product suggest and based on what I've learned it's kind of going against what I've come to believe as good practice for healthy soil. It even suggest expanding or growing additional microbes by using water and molasses with no mention of aeration or any other means of oxygenation. Maybe these microbes perform good things even though they are apparently anaerobic but everything I've researched and learned says that anaerobic is not a good thing. If there were good to be gained why is it suggested to turn a compost pile to allow oxygen? Why aerate compost tea to create an aerobic atmosphere? Why aerate the soil with an enzyme like Nitron or by mechanical means?
Just more stuff that doesn't seem to add up. Someone help me out with this 'cause I'm getting confused. It looks like an easier, softer way to introduce good microbes but is it really beneficial to what we're trying to accomplish?
I'm wide open to theories. Mine is only one.
I think it's someone on another list who uses the following in his signature...
In theory, theory and practice are the same, in practice; however, they're different.
Wow, subywu. You've just opened up a whole new can o' worms with me. I've been pickin' around and there are quite a few theories (all of them proven) that suggest both of us are right. Apparently this is a topic that is still very much wide open. I'm gonna' go dig some more.
There was a report on using milk as a fungicide broadcast by NPR some were around 1999-2000. The report stated sucessful use of milk in controling powdery mildew. The milk was mixed 1 to ten with water. One key point was it had to be RAW MILK. Which can be a problem acquiring as it is illegal to sell raw milk in many states.
The original report of using milk as a fungicide that I saw came from some USDA researchers in Brazil where they found a 50/50 mix of raw milk and water did a very good job of controlling Tobacco Mosaic, probably in the 1980's. Since I have found that a 50/50 mix of fat free milk and water does a very good job of controlling Powdery Mildew, Black Spot, and a few other similar plant diseases that sometimes appear.