Gardening Shorts - Powdery Mildew
- themarigoldgc
- Jul 28, 2023
- 4 min read
Updated: Aug 9, 2023
I went to see our local community garden the other day and what a lovely place it is! This is a perfect time to see it, as well, with all the beds and plots full to bursting with veggies.
One lady had rows upon rows of beets in her garden plot in the ground. Wow! She lets a few go to seed each year as she harvests her own vegetable seeds. I am in awe of both the garden and the gardener.
While there, I went for a poke through of the greenhouse and noticed powdery mildew starting to rear it's ugly head on the melon and cucumber leaves. (Not this one in the picture, this is mine from a couple of years ago. Growing in the hoophouse).
If you get powdery mildew in the greenhouse, you have to deal with it pretty quick or it rapidly spreads from plant to plant, creating quite the nightmare.
What is powdery mildew? It is a fungal disease that looks like grey fuzz or flour that has been dusted on your leaves. It usually starts in small spots, like in the picture above, but spreads quickly over the whole leaf.
How do you get powdery mildew? The spores are spread by the wind, mostly in the late summer when conditions are warm and dry, but the air is humid. Like our weather was last week with the heat but daily threats of rain. Perfect weather for mildew spores.
When do you get powdery mildew? If it happens in mid-summer, while your fruits are still just forming, you want to try to stop the spread.
If it happens in late-summer, when your butternuts, pumpkins, spaghettis, are finished growing and you're just waiting for them to colour up, then you needn't do anything at all. The mildew will not hurt your fruits as they finish ripening off.
Prevention is the best way to control this fungal issue.
1. Plant squash, melons, cucumbers in bright, sunny locations.
2. Ensure that there is plenty of good air flow around them, good air circulation.
3. Water at soil level, try to keep the leaves dry.
4. Water in the morning as sitting in cool, damp soil overnight will promote the growth of the fungal spores.
If it is in the greenhouse, you want to try to stop the spread quickly.
4 Ways to Deal With Powdery Mildew
1. Cut off the leaves as soon as you see the fungal spores happening, to prevent spread. Have a bucket of soapy water with a titch of bleach in it with you and dip the pruners into the bucket between each cut to prevent spread.
2. Milk - Mix a solution of one third milk and 2 thirds water in a spray bottle. Spray till leaf is dripping.
You can use a higher fat content if that is all you have at home but it is a bit less effective, and is quite smelly as the milk sours on top of the leaves. This milk spray works really well on the smooth foliage of roses but is less effective on the hairy leaves of squash, cukes, and melons. This spray will only kill fungal spores, does not harm insects or foliage.
Works better as a preventative spray than a cure, but it works. This is the remedy that I use most.
3. Baking Soda - Mix 1 teaspoon of baking soda in 1 litre (quart) of water and spray till dripping. The baking soda will kill only the fungal spores, does not harm the rest of the leaves. Is also better at prevention rather than a cure. I'm afraid that once you have it, you have it (insert sad face here).
You can also add a bit of soap to the spray to help it stick but be aware that this will also harm any beneficial insects, so only use while they are not active, and do not spray the blossoms. If in the greenhouse, close the door while you spray and until it is dry.
4. Wood Ashes - This is a new-to-me idea but was shared by a very experienced, long time gardener with loads of knowledge, so I am sharing it with you all here as another option.
Mix 6 teaspoons of wood ashes and a drop of dish soap in a litre of warm water and spray the mildewed area liberally.
This will also harm beneficial insects so use when they are not active. If in the greenhouse, close the door while you spray and until it is dry, do not get on the blossoms.
In this picture above, you can see how Charles Dowding just removes the old leaves from the cucumbers as they yellow and age, leaving just the fresh, new leaves at the top for photosynthesis. New flowers are still forming at the top and along the stems. He does not spray with anything. Do not be afraid to prune! Check out this article here for more pics and information.
Tips - do not fertilise and prune off extra foliage to improve air flow around the plant.
Still having problems each year? Look for mildew resistant varieties of vegetables! They are out there.
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