White powdery mildew on squash leaves, are you having that problem this summer?
I’ve received a bunch of questions recently from people wanting to know how to get rid of white powdery mildew on squash leaves. So I thought I would go ahead and share this cool trick reader Veronica sent in a while back.
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After I told you all about the powdery mildew on my pumpkin patch, reader, Veronica, wrote in about her success in getting rid of powdery mildew. {I would totally try this if my pumpkin patch wasn’t so big, it would take hours to apply!}
I thought it was an AWESOME tip that I would share in case some of you are dealing with powdery mildew.
Veronica wrote:
“My zucchini plants got powdery mildew this year and I got rid of the mildew! As directed by my mother, I combined a tsp of baking soda with a quart of water in a spray bottle. I then shook it up real good so all the soda dissolved.Then I sprayed each infected leaf each morning until the spots when away. My plants are now back to producing (albeit slowly) zucchini. I live in Mukilteo, WA, so it should work for you too. You’ll want to spray your pumpkin plants each morning. Good luck with that!”
That’s awesome that you were able to save your plant, Veronica. And thanks for sending in the tip!
As a side note, powdery mildew can overwinter too. So make sure to clean up all the leaves and plant debris out of your beds in the fall.
Also, in the interest of prevention for next year, avoid overhead watering {i.e. sprinkling the leaves}. Also try making plant spacing less dense to increase air circulation.
Does anyone else have this problem? How did you get rid of the white powdery mildew on your squash leaves?
~Mavis
P.S. If you’re looking for some tried and true tips for growing winter squash with stellar results, pop on over to my article about How to Grow Winter Squash. There’s a lot of great info over there. 🙂
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Charla Echlin says
Oh yeah, that showed up as soon as our weather changed- it rained, got humid and the sun stayed behind the clouds. Perfect recipe for powdery mildew. First I removed infected leaves, and when it continued to progress, I then used an organic fungicide- spraying top and bottom of leaves- and I think I got it in time 🙂 My squash is doing well. But I think next year I won’t plant them under my bean teepees- My beans got a little out of control and limited the air flow.
Melissa says
My cucumbers got it bad. I ended up just pulling them out. (they were about done anyway)
CJ says
I wonder if you could use a clean hose attachment (like the kind usually used for pesticides) and put this solution in there instead for large patches of squash?…
Mistie says
That’s a really good idea and it wouldn’t really take that long if you mixed it in a bigger quantity and used one of those 1 or 2 gallon garden sprayers. The sprayers are only $10 at walmart, home depot, lowe’s, etc. Whatever you want to mix up, you can and it’s quick to use.
lavendersbluedillydilly says
yeah, yellow squash, zucchini, AND my cukes got is all bad this year, I did not know that it overwintered! I will try this for sure! Thanks!
Steve says
I have a vineyard and we battle PM all season long. The only way to keep it away is spraying with micronized sulfur about every 10 days. It’s organic. If you get it, use MIlstop (Potassium Bicorbonate) to try and remove it before it gets too bad. It’s also organic.
Margo, Thrift at Home says
ah, this is what killed my pumpkins! I like this solution – I would send my kids out to do it and they would love that job. We have a shady-ish yard and humid summers, so I can see how powdery mildew would be a problem.
Kim O. says
I live in the northeast by the water. It gets very humid and damp around here. Major problem this year. Pulled some stuff out because it got so bad. I did do some baking soda spray, but it’s hard to keep up with it. Now some of my plants seem to have verticullum(sp)? I worked so hard this year, these diseases really get me upset. I had a event crop of zucchini, not so good on the cukes, and got about ten sugar pumpkins from three plants…I’ll take it.
Krista G. says
Mavis, have a watering ? for ya. We’re in the Oregon high desert, so hopefully no mold. The house we bought has 1.5 acres of grass and it’s nuts with a push mower lol. Thankfully, I have horses that mowed it for me this week because I was done!! So, I was thinking of doing raised beds that I can drape when freezing, but wondered how you watered. Our entire property has a sprinker and drip system. With it being so dry here, I anticipate watering every other day….so drip or sprinklers for raised beds?
Patty says
I live in Norcal and I have a raised bed……I use drip lines….my teenage son installed. I LOVE it.
Ray says
Hey, Klamath Falls here and always have problems with PM in the squash. We are just about as high dessert as you can get. I also used to have 9 acres of grass and irrigated out of the Williamson River, (with water rights) and often moved with a gas, no-powered push mower for the exercise. LOL. That grass sure liked river water, especially towards the fall as the algae count in the river rose.
Jen says
Somewhere along the way I swear I read that this powdery mildew can also be caused by lack of sufficient sunlight and over watering. Anyone else come across that? I’m in Bellingham, WA., and these two factors seemed spot on for the reason my zucchini came down with a case of the ‘dew a couple years back.
D Robertgs says
I have the mildew on my zucchini and we have nothing but sun.
Tom says
Me too, I’m in a semi desert, and I have PM every year. Didn’t know it over wintered, does explain the spread when I plant squash types in the same beds.
Sara L. Tilus says
I planted one zucchini 3 ft free space around it stung it up to trellis for air circulation in full still got powdery mildew.
Michelle Wrigth says
My various squash plants and pumpkins all got it 🙁 My cucumbers did not, wish is odd as they are pretty close to some of the squash. Didn’t know it could over winter, thanks for that tip, I’ll take care of it more closely now.
Leslie says
We dealt with it using neem oil. I used a pressure sprayer and mixed it as directed on the bottle then sprayed all the leaves. It only took two applications and they were all healthy again. It also got rid of all of the harlequin beetles and flea beetles on my broccoli and cauliflower this year, which were totally destroying my entire garden. It was our first year gardening on our new land and its tough clay soil, and we have a lot of work to do to get healthy soil and healthy plants.
D Roberts says
did you spray under the leaves or just from the top
Jamareo says
So you sprayed neem oil or neem oil and banking soda?
Marcy says
Not an issue here because it’s SNOWING. Seems really early this year.
Mavis Butterfield says
Holy cow, what state are you in?
Marcy says
Anchorage, AK.
Amy says
I also used Neem oil which can be purchased at most home improvement stores (Lowes, Home Depot, etc). I like it because it is 2 in 1 product…pesticide and fungicide and is organic. You can harvest the same day you spray, no scary chemicals. If you spray as soon as the powdery mildew pops up it will almost kill it over night. It also helped me fend off the stink bugs, mites, and aphids. All you have to do is get one of those gallon size sprayers. It’s also great for the fuzzy white mold that grows on indoor house plant soil. Downside for some is that it kinda smells like garlic. I like the Garden Safe brand…their Neem Oil label says…”This product controls the following: Fungus – rust, leaf spot, anthracnose, scab, black spot, downy mildew, botrytis, needle rust and flower, twig and tip blight, alternaria, powdery mildew. Insects – aphids, spider mites, scale, whiteflies, beetles, leafrollers, other insects”
Karen at A Glimpse Into My Reveries says
Be careful when using neem oil as you can also kill pollinators like honey bees, too.
Mavis says
Thanks for the reminder Karen!
D Roberts says
I information I read said as long as it has dried it is no longer a hazard to bees etc. It seemed to come from a reputable site.
Kimber says
Neem oil is not harmful to bees! Bee keepers have attempted to use it to free bees of mites! It only kills the bad bugs that eat the plants. The good bugs don’t eat the plants so they aren’t affected. 🙂
Laura says
re: “harvest the same day”… If anyone who will eat the vegetables is trying to get pregnant, it’s important to wash the vegetables after you apply neem. Even though neem oil is a natural, biodegradable substance, anecdotal evidence floating around on the web suggests that if neem is taken internally, it MIGHT temporarily reduce human fertility, and might temporarily increase chance of miscarriage. Anecdotally, the effect on fertility isn’t strong enough to be relied upon as a birth control method, and wears off rather quickly (so eating neem now won’t affect you down the road). Just wanted to throw that out there in case.
Froggirltx says
Snowing here, too…Fairbanks, AK. Some squashes naturally have the silvery-looking color to parts of their leaves. We had some zucchini type squash this year like that. But, all that is now behind us.
Gwen in L.A. says
I used to use skim milk (reconsituted dry milk) which works ok for PM. A mix of 1 tsp sodium bicarbonate per cup of water works very well. Los Angeles is a dry climate, but with late summer rare humidity, we did get a lot of mildew on the squash. Neem oil has it’s place, but it is not something I keep on hand. Baking soda is also much less expensive and easily available. Results w/in 48 hours.
Libby willis says
Someone said to mix 1 tsp of baking soda with 1 qt.of water using a spray bottle each morning but another person said to use 1 tsp of baking soda in 1 cup of water and it would be gone in 48 hours.Which is it? I would like to do this instead of Neem oil if it is effective.
Michele (Carrollton, TX) says
Woo Hoo! Now I know what that powdery looking stuff on my canteloupe is. To the store I go today…gonna try the neem. This issue just popped up about a week ago so hope I caught it in time. After field mice destroyed my canteloupe crop and pea crop I was sure they were gonners…till I get rid of the pests early September. Now I have new peas and canteloupe growing so I don’t need some fungus destroying them now!
tracie says
I use neem oil in a 2 gallon sprayer 2 x then maintance cleared it up. I do spray late evening as to avoid killing honey bees.
Nancy says
Does P.M. overwinter in the soil? What do you do then? Can you put infected plants in the compost?. How about the squash that seems fine to put in compost? I plan to plant squash in a different place next year but wonder what I can plant in the P.M. spot next year?
Deana says
A solution of watered down milk will also kill powdery mildew. Ended up with it a few years ago in starts I had purchased. They were small enough that we just dipped the leaves in the milk and it was completely gone with one treatment.
Diane says
My zucchini leaves are healthy and strong, but I do have several that are grayish. However, it is just the color of the leaves. There is no powder. They are also supposed to be a mildew resistant variety. My question is: if the leaves are gray in color and not powdery and otherwise healthy, can it be normal?
Amber says
I have something on my zucchini plant that looks similar to powdery mildew, but doesn’t seem to be on top of the leaves. It looks as if it is in the leaves. Oddly, it doesn’t seem to affect the production significantly. I have tried taking off all of the infected leaves, and spraying it with neem oil for 3-4 applications, but it does not seem to make a difference. The spaghetti squash plants 10 feet away got obvious powdery mildew, and the same treatment got rid of it right away. Any idea what I might have on the zucchini plants? I can’t find anything similar to it in google images.
Cori says
Might it be “silvering” of the leaves? My squash leaves looked sort of grey silver, with no powder for a while, I found some info a while back about silvering. My plant was smal then, I did nothing to treat it as I could not find anything online to say it was bad, and the plant is fine now.
Laura says
I used Garden Safe Fungicide 3 with Neem oil. A ready to use spray. I had the powdery mildew and yellow splotches. I sprayed right before dark and by the next afternoon the leaves had brown splotches all over. Not sure what happened. Has this ever happened to anyone using this type of spray? Frustrating.
Holly says
I know this is older but I thought I would share my method as well. I radd a study from the University of Colorado that said milk in a mixture of one part milk, ten parts water. I tried it myself with success. I mex it in a gallon sprayer and spray once a week. I drink whole milk, but I actually switched to a combination of Kieffer and water 50/50 and then one part of that to ten parts water. Kieffer has almost no lactose(sugar) but is higher in probiotics. Then, I ordered a raw pro biotic that was guaranteed to be active and alive, with many more strains than my keiffer supported an it worked even better. PM is a DNA specific mildew. Each strain only attacks one plant host. Similar plants it can eventually mutate to ingest that plant as well( like cuces and squash) once you see the mildew, it has replicated in the DNA of that plant and will continue to need treatment to keep it at bay. A great preventative measure to take if you ave ad problems in previous seasons is to alternate spraying once a week from the start of your garden. Once week a solution of dawn soap 1tsp per gallon water, and then the dairy the following week. The soap will kill bad pathogens and bugs, while allowing the good stuff to live, then the milk adds good bacteria to help the plant with its natural processes. Fruit ends up less pocked as well. Snohomish WA over here.
Roan McClure says
I am in Cave Junction OR and have PM on crookneck, zuchinni, hubbard squashes, cukes, and melons this year. Knew nothing about it last year when it was on the zuchinnis only. I removed the leaves and vines and burned them last year. Must be in the soil. Is there anything I can put in the soil when I rototill this fall that will help get rid of it? It didn’t bother the onions, garlic, asparagas, herbs, or new red and yukon gold potatoes.
Alexandra says
Hi Mavis,
I thought you might like to know that your first picture up above does not look like a picture of downy or powdery mildew. Rather, it is squash silverleaf disorder which is supposedly caused by white fly larvae feeding on the plant when it’s a seedling. I researched this like crazy when it happened to several of my squash plants and was relieved to learn that it did not cause any harm to the plant in terms of impacting production or killing the leaves. And there is no treatment that I am aware of. I had some beautiful squash plants with these silvery leaves that were totally thriving (until they were killed by vine borers..). The other pictures do look like powdery mildew that would need to be treated.
Cheers, Alexandra
Ronald Esh says
I live in Kenya. And I have lots of this mold on my squash. First time I’ve ever had this. Will watered raw milk work. No chemicals available near me.
Mark Hannon says
Neem oil didn’t solve my powdery mildew problem. Followed the mixing instructions and applied several times. Squash plants still all died after leaves turned to leather. Will try the baking soda recipe.
Jennifer says
I use a Neem Oil concentrate and mix it with water (I believe it was 2oz per gallon of water) I use that to spray for the powder mildew and it’s also gotten rid of the spider mites (weird little red bugs that create huge webs all over my tomato plants) when used every 3-5 days.
Mary says
Very relevant post today, With all the rain we’ve been getting. On another note, I’m taking a baking class at King Arthur on Sunday! My very thoughtful daughter gifted me for Mother’s Day. So excited and wouldn’t have known about them if you hadn’t posted!
Carol says
We use the baking soda in a quart of water method. We find it very effective here in the PNW. If using Neem, be sure to use it very early in the morning before the pollinators are out, so the leaves can dry and any “drift” settles.