Milk may erase powdery mildew fungus

Q. Can I use milk as a fungicide on my cucumbers?

Dan from Poland

A. Powdery mildew is easy to identify with its powdery white patches on the surface of leaves and stems.

There are several closely related fungi that cause the problem with a specific powdery mildew fungus attacking a specific plant species or family.

Although many plant-attacking fungal diseases require water on plant tissues to occur, powdery mildew needs only high humidity. Frequent rain will actually inhibit its growth.

Plant health is the first line of defense against this problem. Select cucurbit plants that show some resistance or tolerance for the disease.

Seed catalogues indicate which varieties are resistant to which pathogens.

If buying plants at a nursery, the plant tag should contain this information. Examine the plants you plan to purchase to be sure they are healthy.

Plant in a proper location with attention to light, soil and moisture. A soil test will determine the need to adjust pH or add nutrients.

Space properly to allow good air circulation, and allow sunlight to reach most leaves.

For cucumbers, growing on a trellis structure will speed the drying off of leaves in the morning.

Be sure to remove weeds and use trickle irrigation which will not increase humidity.

If the problem continues to persist, reaching for a fungicide might be the obvious solution. For several reasons, this may not be the best answer.

A fungicide effective against powdery mildew must be used and application directions followed carefully.

Resistance to fungicides has been noted, and the effect on the pollinator population is cause for concern.

Then, there is using milk as a fungicide.

Several studies have been done as to the effectiveness of treating powdery mildew with milk spray, and the data collected shows it is effective.

A ratio of four parts full strength powdered milk to six parts water, mixed immediately before application, was used. Diluting the milk reduces the residue on the plants.

To reduce plant stress, treatments were applied in early morning or late evening.

The spray was 50 percent to 70 percent effective in reducing symptoms on pumpkins with a low level of infection.

Whey has also been tested and reduced disease on cucumbers and zucchini.

So it’s not 100 percent effective. Thus, working to ensure air circulation around plants and sunlight penetration into the garden is important.

For further reading or for research go to http://go.osu.edu/powderymilk.

Today’s answer is by Merabeth Steffen, OSU Extension master gardener volunteer. Submit questions to the clinic at 330-533-5538 or drop samples off to the OSU Extension Office in Canfield.