I regularly use neem oil in my garden to help suppress the presence of white flies, aphids and certain soft-body caterpillars. I'm curious if neem oil can be effective in addressing powdery mildew on cucumbers or pumpkins. I'm in NY zone 7a and grow in raised beds using organic methods (best I can).

  • I just ordered some neem oil for slug prevention, hadn't heard that it could be used for powdery mildew. I've only used the dishsoap/baking soda/water mixture for cucumbers and does the trick every time. I know that doesn't answer your question, but I am interested to hear if you try it how it works! Commented Jun 25, 2020 at 19:08

3 Answers 3


It can be used for treatment of powdery mildew, but there are other, useful non chemical treatments too, such as milk. 1 or 2 parts dairy milk to 9 or 8 parts water, mixed in a sprayer, or alternatively, baking soda and oil mix. Further information on these types of control here https://www.growingformarket.com/articles/powdery-mildew-solutions#:~:text=Neem%20oil%20is%20labeled%20for,to%2014%20days%20is%20recommended., but note these are treatments for powdery mildew, not downy mildew.

  • That's very interesting.... why do you consider neem oil a chemical treatment? I've always thought of it as a natural/organic solution to many issues within the garden. I use natural cold-pressed and make sure it has the highest azadirachta content.
    – JRap88
    Commented Jun 23, 2020 at 20:15
  • I don't consider it a chemical (as in pesticide) treatment; if you read what I said again, I simply say there are other non chemical treatments too.... meaning as well as neem.
    – Bamboo
    Commented Jun 23, 2020 at 21:49
  • @JRap88: Note: various organic treatments are chemical. Organic (in this sense) just mean without product from chemical synthesis. Maceration, evaporation, filtration, "under the sun", etc. are valid organic and, at same time, chemical methods. -- best method is to reduce use of all such stuffs. If the plants are healthy: cut away the leaves with mildew. Check why do you have so much flies and aphids, etc. Improve your irrigation (not on the leaves) and soil, etc. Commented Jun 24, 2020 at 13:27
  • @Giacomo Catenazzi Thanks for that comment. Would you happen to know what attracts or causes a plant to be come attractive to white flies aphids etc and what I can do to determine this.
    – JRap88
    Commented Jun 25, 2020 at 15:10

The best way to get rid of powdery mildew is to spray the leaves with Lysol. I have used Lysol for fungal problems on many plants plus I have used it to get rid of the botrytis mold that can often grow on the surface of the soil of houseplants. Lysol is generally safe on most plants.

Another way to suppress populations of insects, like aphids, is to mix a few drops of dish washing liquid with water (I use distilled water) in a spray bottle and spray the plants thoroughly. I usually spray infected or susceptible plants about once a week.

  • Lysol is tough to get at the moment. Also I assume this isn't organic? I'm not sure.
    – JRap88
    Commented Jul 3, 2020 at 4:07
  • That is a very good question that I didn't know the answer to. I did some research (which was calling my sister, who is an avid organic gardener, so I don't have any source to site). Lysol is not considered organic. Some organic methods include ; vinegar, baking soda, peroxide and Neem oil. I have just always used Lysol because it is quick, easy, non toxic and very effective.
    – Avlar
    Commented Jul 3, 2020 at 16:53
  • Yeah it's a odd one because you can clean a food prep surface with Lysol and eat off of it. So it has to be somewhat safe. Idk. To me organic is a concept that isn't 100% perfect.
    – JRap88
    Commented Jul 3, 2020 at 22:03
  • Well, you can clean a food prep surface like a table that typically has a sealant on it and isn't porous, so you're not actually ingesting that much. We're talking about the leaves of cucumbers and pumpkins here, which are incredibly porous, and are partly responsible for the overall health of the plant. Even though you don't consume them, it's quite likely that any chemical that enters the foliage will also affect the flowers and therefore the fruit. Commented Oct 9, 2020 at 6:07

Neem oil is excellent for powdery mildew. It's indicated for that usage on the bottle and is mentioned in articles on powdery mildew prevention. I used it for the first time this year and for the first time, my squash and cucumber foliage was powdery mildew-free. It's also excellent for organic gardening, unlike some of the other suggestions here. (Please don't spray your vegetable foliage with Lysol. Please.) And it's affordable. It was a few sprays per leaf with a 24oz bottle that retails for $10USD on Amazon.

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