Preventing Powdery Mildew On Cucumbers, Squash & Melons

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Powdery mildew can be a real problem in the vegetable garden, especially for cucurbits such as cucumbers, squash, melons and pumpkins. Powdery mildew is a fungus that forms as a white or gray powder on the leaves of plants causing the leaves to become deformed and die. It is far more probable in areas that are damp, are somewhat shady, and have higher levels of humidity.

It is difficult to control powdery mildew once it begins spreading on the plant leaves. This makes it very important to use proactive measures in your vegetable garden to prevent powdery mildew from forming if you’ve had powdery mildew issues in the past. Here are some ways to prevent powdery mildew from overtaking your cucurbits.

Steps For Preventing Powdery Mildew On Cucurbits

powdery mildew cucumbers

Here are some general guidelines you should follow in your vegetable garden to help prevent powdery mildew.

  • Select curcubits that are powdery mildew resistant, like the ones listed below:
    • Cucumber: ‘Diva’
    • Yellow Summer Squash: ‘Success’, ‘Sunray’, ‘Sunglo’
    • Zucchini: ‘Ambassador’, ‘Wildcat’
    • Pumpkin: ’18 Karat Gold’, ‘Gladiator’
  • Plant cucurbits in full sunlight. The powdery mildew spores have a difficult time surviving in direct sunlight.
  • Provide plants with sufficient spacing. Cucurbits need proper spacing to increase air circulation and to help prevent powdery mildew spores from spreading from one plant to the next.
  • Disinfect any tools after working around cucurbits. If you use a tool around summer squash, for instance, disinfect the tool before working around cucumbers. If the tool isn’t disinfected properly the powdery mildew spores could mistakenly be passed from one plant to the other. Disinfect tools with full strength vinegar or a solution of one part bleach to nine parts water.
  • Avoid watering cucurbits in the evening. Allowing the leaves to remain damp over night can increase the likelihood of powdery mildew. Water plants in the morning so the leaves have a chance to dry out before dusk. It is better to water the soil around the plants and avoid getting the leaves wet.
  • If leaves begin showing signs of powdery mildew ( small white or gray spots on leaves) remove the infected leaves from the plant and discard in trash. It is not recommended to place infected leaves in a compost pile.

Homemade Sprays Containing Milk and Baking Soda

One of the simplest and most cost effective ways of preventing and controlling powdery mildew is using a spray of milk and baking soda, applied directly to the top and bottom sides of the plant leaves. The baking soda will increase the pH levels on the leaf surface which will make it difficult for the fungi spores to survive.

It is unclear how the milk actually affects the powdery mildew spores, but spraying milk on infected plant leaves with a solution of nine parts water to one part milk has shown to decrease powdery mildew by 90%. It has been reported that milk can boost the plant’s immune system, which also helps to fight powdery mildew and other diseases.

I have used a solution of milk, baking soda, and liquid dish detergent to effectively control powdery mildew in my own vegetable garden. Here is the spray recipe I use:

  • Using a hose end sprayer, remove the bottle from the sprayer.
  • Fill the bottle with 1/2 quart of milk (I typically use skim milk, but any milk will work)
  • Add 3 teaspoons of baking soda
  • Add one drop of liquid dish detergent
  • Mix contents well
  • Reattach bottle to sprayer. Attach sprayer to water hose and spray the top and bottom sides of infected leaves
  • Reapply solution once a week

If you typically have issues with powdery mildew on your cucurbits, I think it is important to begin treatments using the milk and baking soda sprays before the powdery mildew sets in. Using the spray before the symptoms of powdery mildew are seen is critical in preventing it from forming in your vegetable garden.

How do you prevent powdery mildew on your cucumbers, squash and melons? Please share your powdery mildew controls with us!

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Comments

  1. JohnI Schooler says:

    I volunteer at Leu Gardens here in Orlando. We have a demonstration vegetable garden. Powdery mildew is really tough to control here due to the frequent rain and high humidity. Today I noticed that the horticulturalists have taken a large piece of aluminum foil and cut a slice into it from the center to the outside edge. They then placed this under the plant with the center at the base stem of the squash plant. I’m going to try this in my own garden and I may also try the milk “potion” suggested y. Happy gardening!

    • Hi John, thanks so much for sharing the trick with the aluminum foil. That’s very interesting. How does the foil prevent powdery mildew? I guess the mildew has some type of reaction with the aluminum?

      Let me know how the milk and baking soda works for you! It does wonders for preventing and control powdery mildew here.

      Thanks for your comment and have a great day!

      • I’ve heard of this as a control for squash bugs. The light reflected from the aluminum foil disorients the bugs and makes the plants undesirable places to live. I don’t think it’s a fungus control.

  2. Will Metcalf says:

    Going to try the milky spray on my pumpkins and will report back on it’s efficacy.

  3. Brad in Michigan says:

    First time veggie gardener here….I started to notice some powdery mildew on our pickling cucumber plants and have found many internet success stories from using just the 9:1 water to milk ratio so I am going to give it a try and see how it works. We also have lots of squash and zucchini plants so I want to keep it from spreading to those as well! Thanks so much Tee for an awesome and informative site!

    • Hi Brad – Sorry to hear about the powdery mildew. The milk & baking soda spray has worked well in my garden. Just make sure you apply it in the early morning over in the afternoon or evening. Let me know how it works for you!

  4. How often should this be sprayed? Thanks.

  5. Charlie Crab says:

    Hi I have Powdery mildew on my Cucumbers, I live in the tropics of North Qld Australia, I will try the milk and report back

  6. Brad in Michigan says:

    Hi Tee! It has been a couple of weeks now and I have done a few applications using just milk and water at about a 25% milk concentration and it seems to be working. The mildew does not seem to be spreading any further and some of the leaves that only had a little mildew on them seem to have cleared up. A few of the leaves that were pretty far gone ended up shrivelling up so I just trimmed them off. I’ll keep ya posted…. thank you for all of your work on your sites to help us amateurs out! Much appreciated!

    • Hi Brad – I’m glad the spray has helped your plants! Yes, the leaves that have a high concentration of mildew should be trimmed. The spray, or anything else, will not help them once they get to a certain point.

      Good luck and have a great day!

  7. Last year it was squash bugs, this year it’s mildew. I’m gonna’ try this.

    Norma from Idaho

    • Hi Norma – This spray has helped quite a bit for powdery mildew in my garden. Make sure you only apply the spray in the early morning before the sun rises.

      Good luck and let me know how it works for you!

  8. Is the fungus dangerous to other things. Can I feed the infected vegetation to my chickens?

    • Hi Wally – Very good question. The short answer is ….. I have no clue. I don’t think the mildew would hurt the chickens, but if given a large amount, I’m not sure. A little here and there might be OK, but I’d be hesitant about giving them leaves that are covered in it.

      • Parasitic fungi are very host specific if it is a plant pathogen it will not harm your chickens. Thanks for the milk tips guys I’m going to try it out this week.

  9. I have had mildew and squash bug issues for years inspite of rotation as far away as 100 feet. This year I used this mixture but got it wrong with the portion of baking soda. I burned the leaves badly. Since then I corrected the formula and the plants have shed or I have removed all the leaves over time. The plants didn’t start producing until recently but they are doing great now. I treat them weekly, no sign of mildew. As far as squash bugs, without DAILY egg and bug searching, it seems hopeless. Still waiting for someone to post the magic bullet for these pests. I am going to try to put at least a teaspoon of b.soda in my compost tea foliar application to keep the ph to alakline.

    • Hi TJ – Squash bugs are very difficult to treat. The best thing I can offer is to diligently check the bottom of the leaves for squash bug eggs and to use a spray called Pyrethrin. Pyrethrin is derived from a plant and safe to use on veggies.

      Did the formula I gave above cause your leaves to burn, or was it some other formula? It is also a good idea to only apply it during the cooler morning hours. Never apply it in the heat of the day. Early morning on a cloudy day is ideal.

  10. Hi Tee – It’s been a little over a week since I tried the milk solution. I’m happy to report that the one squash plant that I was ready to pull has lots of green leaves and two little crooknecked squash. I’ll be armed for next year.

    New problem…the winter squash I plated has lots of flowers each day but has yet to produce any fruit. I haven’t seen any bees around since the first part of the summer. Do you suppose that’s the problem? I’ve taken it upon myself to transfer pollen via a plant brush. Any suggestions?

    • Hi Norma – I’m very glad to hear your squash are doing better! I hope you enjoy your upcoming crookneck squash.

      It definitely sounds like a pollination issue with your winter squash. If there are no pollinators visiting your blooms you may need to resort to hand pollinating them.

  11. Tee, When using hose end sprayer, are you filling the rest of the jar with water or just using that concentrate and letting the sprayer mix the water? Thanks for all your work.

    Ray

    • Hi Ray – I fill the jar with the milk (plus baking soda and a drop of dish detergent) and ley the sprayer mix in the water. There are many different hose end sprayers and the settings can be different on different models. I usually start out with the sprayer set to the middle setting. There are some that give the option to set ounces per gallon. If you have one of those then I start with the 2 ounces per gallon then adjust as needed. You can set it to the max setting (usually 8 ounces per gallon), but you need to reduce the amount of baking soda by about half. This has worked well for me in the past.

  12. Forgot to mention that I painted the solution on the leaves. I only have three squash plants and it was easy to do.

    I’ve bookmarked your site and have referred to it for several other plants and plant issues. Thanks!

    • Hi Norma – That’s a very interesting way of applying the solution. I’ve never tried that before. I’m glad it had worked well for you. Thanks for sharing your experience!

  13. Scott Estell says:

    I have used the Copper Sulfate solution in the past. It is sooo expensive but it works. Especially when it rains & you have to re-apply. Our Squash,Pumps & Cukes have it now real bad. I will give your Milk/soda solution a try. I’ll report back in a few weeks. Wish us luck

  14. Just discouvered your site while looking for powdery mildew solutions on my squash and cucumbers, first application was today. I will keep you posted.

    Thanks for the info and a great site

    British Columbia

  15. Hi – I have a terrible problem with powdery mildew on my summer squash and pumpkins. Glad I found your site! I will try the milk solution. I removed a LOT of leaves last night. There were new little leaves coming up beneath them, so hopefully those will take over soon and the plant won’t be too stressed from all the pruning. It seemed like a LOT of pruning! Mary in Los Angeles.

    • Hi Mary – Removing the infected leaves is an excellent idea. They need to be removed to decrease the rate of spreading. Let me know how the milk/baking soda spray works for you!

  16. When removing squash leaves, how much,if any, of the long stem should be removed?

    • Hi T.J. – If you are removing some leaves from the squash plant you can remove the stem all the way to the main stem it branches off of. It will not re-grow a new leaf so you can remove it.

  17. I just found powdery mildew on my crooked neck squash. I am in NW Oregon. I will try your treatment and remove the existing disease leaves. I planted my pumpkin, summer & winter squashes too close together! Should I pretreat the whole bunch of it or just the ones showing powdery mildew? Will my zucchini get this too? Thanks and I will let youknow how it works.

    • Hi Helen – Yes, you can pre-treat your other plants to prevent them from getting powdery mildew, but I would reduce the amount of baking soda by half for those plants. Zucchini can get powdery mildew too.

  18. Got powdery mildew on my pepper and tomato plant. Removed quite a few leaves, but I’m going to try the 9:1 (water/milk) milk, today.

    Heat, snails, and now powdery mildew are crushing my vegetables.

  19. I am a first time gardener in Souther Californina and I have powdery mildew on my pumpkins and yellow crockneck squash. I will be trying the milk solution and trimming the infected leaves. In the meantime, is the fruit that is ripening now still edible?

    • Hi Carrie – Good luck with treating the powdery mildew. Let me know if you have any issues and also your successes. The fruit are still very edible. The mildew affects the plant itself and not the fruit. Keep in mind there are mildews that can affect the fruit but not powdery mildew.

  20. Does the powdery mildew on my Lil’Pump-Ke-Mon winter over? Are there things I should do to prevent a reoccurrence next year?

    Thanks if anyone has the answers.

  21. Hi Tee,

    Just to let you know – we had this problem in mid August and used your solution – - of course we put it on at the end of the day (ooops!) and we did cut back the infected leaves – worked like a charm. Now I am going to reapply (in the morning tomorrow!) as I see today some spots coming back on the one squash that was infected. It never spread to anything else, but I guess that is because we removed the worst leaves and sprayed the whole plant and the other plants as well. THANKS! This WORKS!

  22. Hi Tee,
    Despite my best attempts, powdery mildew has taken over my entire pumpkin plants. However, I do have 3 fairly good sized pumpkins. One is mostly orange but the other two are quite green. Should I pick them now even though it is a month before Halloween? The pumpkin vines look quite shriveled and I don’t think they are getting much nutrients. I have read on some other sites about treating them with a 10% bleach solution and putting them in the sun so they will hopefully turn orange and not rot. What do you suggest? We live in Denver, CO so the climate is fairly dry. I was also wondering if I should treat the soil over the winter to avoid getting PM and if so with what?
    Thanks so much for taking the time to make this great website,
    Dana

  23. Hi Tee, My garden was taken over by the powdery mildew last yea. I wish I had know about milk remedy. Now I am ready to start the garden for this year but I am afraid that the soil is contaminated with the left over infected cucumber plants from last year. Is there any way for me to treat the soil before bringing the new plants in?

    • I was hoping for an answer to your question about the soil because I’ve been worrying about that, too! I just moved to the running up Rain City in the country, and didn’t know what was happening (this mildew) until it was way too late. I am digging up many flowers and throwing them away, but am very paranoid now about my tools and soil. I’m also wondering if I can rescue some root systems of plants that were so moldy. I tried digging up a few, washed them in the home-made fungicide (using a different recipe-just found this site), base (threw entire stem system away) and roots, rinsed with water, and then re-potted in loose soil. I did not put them back in the ground yet, since I don’t know what to do about all that dirt. Well, I suspect I should just throw it away anyway, because my guess is that it’s too clayish for this climate, and I need to replace it all with some sand/soil combo for great drainage (?). But the contamination thing has me paranoid, too. Thoughts?

  24. I am going to try the milk and baking soda solution…..I lost my first crop of yellow squash and zuccini and cucumbers to this molding on the leaves, everything was fine then BAM the veggies started and fell off and the plant died. Re-planted soon after but in a different spot, thanks for the tip i will try it and let you know how it worked. Thanks again.

  25. Anonymous says:

    Be careful about the baking soda. It helped the first couple of times, then somehow my winter squash plants started “burning” with a reddish splatter pattern even though the concentration was similar. I rinsed the plants as soon as I observed damage, but the spots turned white over the next few days as soon as bright sun came out. I am trying the milk solution instead. I have used a 1:4 milk spray twice in the last week but it rains every day, and the mildew is getting worse. I have not had issues with powdery mildew on these plants except when it rains multiple days and the temperature hovers in the 80s, it seems to have a hard time surviving multiple full sun days of 90 degrees with only water to the roots of the plant. It is getting to the point where there are so many slightly infected leaves it would hurt the plant to remove them.

  26. Hello Tee,

    I used only baking soda on my plants and they starts burn right away. I want to try your recipe, but I have a very small garden. I am wondering if I can use spray bottle instead of using sprayer.

  27. I tried this remedy on my pickling cukes and it worked like a charm! Thank you, Thank you! I thought I was going to lose the whole crop.

    I do not have a hose end sprayer as mentioned above so I used this recipe: In a 32 oz container, mix 2/3 cup milk (I used 1%), 1 tsp of baking soda and 1 drop dish detergent. I topped the container off with water and applied to the leaves using a spray bottle. I removed the most badly affected leaves and sprayed all the rest with the solution and it cleaned it right up. I reapplied after a rainstorm a few days later.

  28. Thank you all so much for your comments. Just finished pruning newly infected leaves and I plan on applying the baking soda/milk/dishsoap potion tomorrow am. I used milk only last year with so-so results. I’m guessing the baking soda is the magic ingredient. I also read that crushed garlic in the solution helps. Any thoughts?

    Any idea if it’s ok to mix the potion in with my fish emulsion foliar spray? I have one that is plain fish oil and one that has sesame oil in it, which I was guessing might help everything to coat the leaves longer.

    We’re expecting on heck of a storm today, so hopefully I’ll have plants left to tend!

  29. CS Zheng says:

    Hi Tee,

    According to your recipe, how much water needed if I use a Chapin RB2000 pressure sprayer to spray?

    Regards.

  30. Two questions:
    1. is the fruit from the squash that is infected with powdery mildew still edible?
    2. is this a problem that lives in the soil, or can I try again in the same spot next year?

  31. I want to try the milk and baking soda treatment as a last resort for zuchini and summer squash plants that are heavily infected with powdery mildew. Can this be done during extreme high temperatures? Our daytime highs are and will be around 100 for the near future.

    Thanks, ann

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