Show notes
Replay 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
Thank you for listening and downloading the show.
Topics: Joey and Holly talk about growing great garlic and dealing with powdery mildew, guest Lee Reich of http://www.leereich.com/ founder of the weed less gardening method
Soft neck, hard neck, elephant, true variety - plant October, 2 – 4 inches in depth – 8 to 10 inches
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 mouthwash as new foliage can be damaged.
Vinegar – Similar to mouthwash, the acetic acid of vinegar can control powdery mildew. A mixture of 2-3 tablespoons of common apple cider vinegar, containing 5% acetic acid mixed with a gallon of water does job. However, too much vinegar can burn plants but at the same time, higher concentrations (above 5%) are more effective.
Sulfur and Lime/Sulfur – Direct contact by sulfur prevents disease spores from developing. When mixed with hydrated lime, the solution will penetrate leaves for even greater effectiveness. A widely available version of this combination includes copper sulphate and hydrated lime, known as Bordeaux mix. However, all of these solutions can burn plant tissue and is damaging to microorganisms in the soil and harmful to beneficial insects. It is also considered moderately toxic to mammals and humans. Use sparingly and with caution if at all.
Milk – The latest player in the fight against powdery mildew is milk. It’s not clear yet why it works so well, but it is believed that naturally occurring compounds in the milk are at work to combat the disease while also boosting the plant’s immune system. One experiment showed good results by applying a weekly dose of one part milk to two parts water.
Water – Ironically, dry conditions and high humidity are the most favorable conditions for powdery mildew to form. But straight water is its enemy because it washes off the spores before they have time to embed. However, water isn’t something that I promote for control because wet foliage is friend to many other plant diseases. If you’re going to try this option, do so early in the day so foliage has time to dry out quickly.
Neem oil – This is a readily available organic option to disease and pest control. Neem oil is extracted from the neem tree, native to India. This is an effective disease control and a broad spectrum, natural insecticide that is kinder to beneficial insects and mammals. As for controlling powdery mildew, results vary but it is not the best option. Results are usually moderate at best.
Dr. Lee Reich is a former plant and soil researcher for the USDA and professor of horticulture, author, and long time avid gardener. He’s mastered the art of weedless gardening, all without chemicals.
1. You don’t till your garden, and neither do we – tilling is very common – why don’t you till?
2. What is weedless gardening?
3. What are the 4 steps to weedless gardening?
4. Why are herbicides bad?
5. How many books have you wrote and if you had to pick one – what book is your favorite and why?
6. How do people find out more about you and your books, etc?
https://thewisconsinvegetablegardener.com/radio/ check out highlights of past show podcast and video https://thewisconsinvegetablegardener.com/video-series/highlights-podcast/
Email your questions to TWVGshow@gmail.com tweet us as #twvg or @twvgshow The show runs March - Oct Saturday morning’s 9-10am cst
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