Can Milk Control Brown Rot?

| 8/28/2008 8:13:03 AM

PlumCut It happens every summer. Just as your beautiful cherries, peaches, plums or grapes start to ripen, disaster strikes. As the disease called brown rot takes over, fruits become covered with a powdery brown coating as they quickly rot and shrink into mummies.

Some varieties are more susceptible than others, but what can you do when you have high-risk fruits that are trying to bear a good crop? Organic growers use sulfur sprays, but frequent use can cause problems in the soil. This year I tried a newer natural method, which involves spraying a dilute milk-and-water solution to suppress brown rot to acceptable levels. It could be a single-season fluke, but my experiment has been a resounding success. 

Why Milk?

In 1999, a team of Brazilian researchers found that weekly sprays of a milk solution controlled powdery mildew in zucchini squash. In more recent studies, milk or whey-based sprays were as effective as fungicides in controlling powdery mildew in two plantings of wine grapes in Australia. Plant pathologists suspect that as compounds in dairy products interact with sunlight, they cause crippling damage to powdery mildew fungi and spores. If milk works on powdery mildew, I thought it might help with brown rot, which has a similar life cycle.  

My subjects were a mature 'Stanley' prune plum and a mature planting of 'Concord' grapes – both easy targets for brown rot and other fungal diseases. In the past, the plum crop was often lost entirely to brown rot, and the grapes typically had half of their fruit ruined by brown or black rot. PlumCluster 

Using a hand-held compression spray bottle, I applied a spray using this recipe:
one-half cup organic low-fat milk
1 quart warm water
3 drops dishwashing liquid (to help the mixture stick)

Beginning in early July, I sprayed the plants five times at two-week intervals. I sprayed in the mornings, covering the fruits and foliage until the spray mixture dripped to the ground. I stopped spraying when the fruits began to ripen, because I didn't want milk residue on the fruits.

Anna Hackman
12/31/2011 5:56:19 AM

I use a similar milk spray as you do for my squash plants. I started from the very beginning and found it kept the powdery mildew at bay. How often do you spray?

Garden House
9/26/2008 12:35:45 PM

Would either of these mixtures work on roses' brown spot and or mildew?

Richard Farrar_1
9/21/2008 8:38:09 PM

I am using a similar mixture of my own making based on my own research and experience. This year it has given amazing control on powdery mildew on grapes with just two sprays 3 weeks apart with the last spray 2 weeks before harvest. Heavy rains do not seem to nullify the effect. Next year I plan to use it from the start of the season as well for control of black rot on grapes, and brown rot on apricots and cherries. I may even try it for apple scab. A two gallon supply of the mixture is made as follows: 1/4 cup of whole milk powder (must be whole milk powder, not skim milk powder, which I get at a bulk food store) 1/4 cup of sodium bicarbonate (baking soda) 1 tablespoon of horticultural oil (the type sold as part of dormant spray kits but any light oil should do) 1 teaspoon of anti-bacterial soap (the oil and soap act as spreader-stickers so that the mixture adheres to the surface in addition to providing anti-fungal benefits in their own right) Directions: Add 2 gallons of water with a sharp coarse spurt of water from your hose to the whole milk powder and the baking soda so that the contents are very well mixed in solution. When the two gallons are nearly fully added, add the horticultural oil, and just before completion add the anti-bacterial soap (if added earlier you get a lot of suds).

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