S2 E26 (segment) Dealing with powdery mildew The Wisconsin Vegetable Gardener radio show

Replay of segment 2 of The Wisconsin Vegetable Gardener Radio Show from 8-25-18 on 860AM WNOV and W293cx 106.5 FM Milwaukee WI,
listen here during show hours Saturdays 9-10 am CST https://tinyurl.com/zvh5kaz
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Topics: Joey and Holly talk about what is and how to deal with powdery mildew.
Providing adequate air circulation will help avoid powdery mildew in your garden
Powdery mildew is one of the most widespread and easily identifiable plant fungal diseases. From vegetable gardens to rose gardens, ornamental trees and shrubs, almost no type of plant is immune.
If you find that some of your plants or trees have powdery mildew, don’t worry. This fungus is host specific, meaning just because you find it on one plant species, does not make it a threat to other type plants in your landscape. Although there are many different species of powdery mildew, the symptoms all look about the same from one to another.
You’ve likely seen it many times. White or gray powdery spots appear, often times covering most if not the entire leaf surface. It’s also found on plant stems, flowers and even fruit. Fortunately, the symptoms of powdery mildew are usually worse than the actual damage. Rarely is it fatal to the plant.
Advanced stages can cause plant foliage to yellow, curl or turn brown and eventually cause the plant to defoliate prematurely. On flowering plants and trees, the fungus can lead to early bud drop or reduce the flower quality.
Conditions that favor mildew formation include dry foliage, high humidity, low light and moderate temperatures. Proactive steps to avoid or minimize this risk include:
Look for disease resistant varieties. Contact your local county extension service for named varieties and cultivars
· Provide adequate air circulation by not crowding plants.
· Site plants where they will get sufficient light of six hours or more each day. Minimize shade and trim trees and shrubs that block the light.
· Avoid over fertilization. New growth is more susceptible. Instead, apply a slow-release fertilizer that provides more controlled growth.
Most conventional products are made for prevention and control, not elimination of an existing infection. That’s why it’s important to start a control program before powdery mildew occurs or at least at the earliest sign of detection.
There are many retail, off-the-shelf fungicide products that are effective at treating mildew. One of the most common active ingredients used for control is “chlorothalonil”. Although effective, it coats the leaf surface with a white milky film that is quite noticeable.
Lesser know options include:

Baking Soda (sodium bicarbonate) -This is possibly the best known of the home-made, organic solutions for powdery mildew. Although studies indicate that baking soda alone is not all that effective, when combined with horticultural grade or dormant oil and liquid soap, efficacy is very good if applied in the early stages or before an outbreak occurs.

Use this recipe to make your own solution—mix one tablespoon of baking soda with a teaspoon of dormant oil and one teaspoon of insecticidal or liquid soap (not detergent) to a gallon of water. Spray on plants every one to two weeks.

Potassium bicarbonate– Similar to baking soda, this has the unique advantage of actually eliminating powdery mildew once it’s there. Potassium bicarbonate is a contact fungicide which kills the powdery mildew spores quickly. In addition, it’s approved for use in organic growing.

Mouthwash – If it can kill the germs in your mouth, certainly the fungal spores of powdery mildew are no match. And that’s the premise. Generic, ethanol based mouthwash can be very effective at control. Tests using one part mouthwash to three parts water worked for well for Jeff Gillman, Ph.D and Associate Professor at the University of Minnesota, Department of Horticulture. Just be careful when mixing and applying mou(continued)