Can Milk Control Brown Rot?


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.

3/14/2019 11:59:47 AM

did you take off all the mummies from the year before? did you spray the ground around the tree canopy to eradicate the mummies on the ground?

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?

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