How to Get Rid of Powdery Mildew on Pumpkins Fast (Ultimate Guide)

So, you need to get rid of some powdery mildew on your pumpkins.

You’re sick of seeing this white fuzz on your leaves.

You don’t know if it’s hurting yoru pumpkins.

And you hate seeing those crisp green leaves get covered with that powder.

Powdery mildew is a common plant disease that leaves behind that signature white powder on your foliage. Pumpkins are extremely susceptible to this disease because of their dense foliage.

It’s no wonder that many newbie gardeners wonder why their pumpkin or cucumber plants are suddenly covered in this ashy texture.

And they don’t do anything about it so it devours their young plants.

Then they give up gardening entirely!

But let’s not let that happen to you.

Let’s talk about how to eliminate this fungal disease from your pumpkin so you can get the harvest you deserve.

Last updated: 11/10/21.

Does powdery mildew affect pumpkins?

Yes, definitely. Powdery mildew has no remorse for squash, pumpkin, wheat, barely, legumes, grapes, onions, apples, pears, gourds, melons, and other dry goods.

PM can also affect ornamentals and decorative plants.

This plant disease actually is VERY common because there’s no single fungal spore that causes it. In fact, there are dozens upon dozens of different fungi that can push powdery mildew to your pumpkin.

The white pumpkin leaves that a lot of newbie gardeners report is the result of fungal spores blowing in from the wind. The disease can also be dormant and spring from the soil.

The term “powdery mildew” refers to a big group of different fungal diseases that all result in similar symptoms- white fuzz on your cucurbit leaves.

The gray to white powdery layer on the plant’s stems, flowers, and leaves are a well-known problem that’ll send any gardener into high alert mode.

How dangerous is powdery mildew?

Although the white fuzz is disgusting looking and leaves behind a white tint on your fingers, powdery mildew doesn’t usually kill established pumpkin plants.

However, younger seedlings or pumpkins that are still just getting their roots built can become affected.

Some common signs of powdery mildew damage to pumpkins are stunted growth, warped vegetation, small leaves, and of course, the white powdery substances on the leaves.

This white fuzz also doesn’t need moisture to grow. All they need is warm conditions, trapped airflow, and shade.

Will powdery mildew kill pumpkins?

A bunch of pumpkins outdoors with powdery mildew.
This mildew is annoying, but controllable.

If your cucurbit is established with a full system of roots, it’s unlikely that it’ll cause any damage to the extent where it’ll kill your plant.

But if you have some youngins that are still growing, you should be very aware and constantly checking on your plants.

You should start a plan to eliminate the fungus immediately. Powdery mildew can wreak havoc on younger pumpkin plants. It doesn’t mess around.

What causes powdery mildew on cucurbits?

This disease comes from fungal spores floating in the air.

During the springtime, we all know allergens, pollen, and spores are amok. When the spores land on a plant that provides favorable conditions, they start to infect the plant and the gray or white spots form on the foliage.

They usually start on the bottom of the leaves and will cover the entire thing eventually.

Poor air circulation leads to high humidity, which encourages spores to form on the plant. Higher temperatures also contribute to spore growth as well as shade from the foliage.

Even after removing all the spores, they can fall to the soil and overwinter into a state of dormancy.

When spring rolls around and temperatures rise to above 60F, they start the process of infesting the host plant all over again.

What’s it look like?

Pumpkins on a field that have been infested with cucurbits.
The white leaves are an easy giveaway.

The signs are obvious.

Powdery mildew looks just like a white or silver powder that covers the leaves of your pumpkin. There’s no mistaking it. It has a signature appearance that any casual gardener knows.

When you rub your fingers across the mildew, you’re left with a streak of powder on your fingers. It’s soft, flaky, and will blow off easily in strong winds. It’s a mixture of different spores from various fungi.

Sometimes, you may not notice your pumpkin has mildew until it begins bearing fruit. There are some other signs of mildew than just the powder.

Other symptoms of powdery mildew are:

  • Stunted growth
  • Damaged leaves
  • Off shape pumpkins
  • Small vines
  • Bud drop
  • Damaged items
  • Whites pots on the underside of leaves
  • Yellow or wilted leaves
  • Leaf drop
  • Poor flavor
  • Pumpkin rots easily
  • Sun burning/scalding
  • Unripened harvests
  • Completely white leaves

Downy mildew vs. powdery mildew

Although these two mildew diseases are similar and any newbie gardener can easily become confused, there are ways to tell the difference.

Downy mildew isn’t a fungus– it’s caused by an oomycete, which is a fancy way for a mold that spawns in water. It’s a pathogen that’s the polar opposite of powdery mildew.

Even though the names are similar, you’ll be surprised to know that if you try to spray one, the same spray won’t work on the other. They’re very different from one another and require different techniques to get rid of them.

The easiest way to tell the difference between downy and powdery mildew is to look for the color of the spots:

  • Powdery mildew causes white flaky specks on the leaves (both top and bottom)
  • Downy mildew causes yellow spots on the top of the leaves and purple spots on the bottom.

If you think your pumpkin has downy mildew, this guide won’t work effectively for you because again, it’s a different pathogen.

What plants does powdery mildew affect?

Powdery mildew affects hundreds of plants, but the most common ones are plants in the cucurbit group: pumpkins, melons, squash, gourds, and cucumbers.

The mycelia come from fungus, with Podosphaera xanthii being the most popular one.

Why does my pumpkin have powdery mildew?

A large pumpkin with powdery mildew.
You may be surprised it’s because of your yard.

This is likely because of conditions in your yard.

This particular mildew is like moist conditions with high humidity.

After all, it is a mildew fungus that needs some wetness to get the spores around.

Both dry and wet climates are perfect for mildew because all that’s needed is humidity in the air for the fungus spores to flow. When it’s hot and dry, fungus mildew can stick onto your plants from winds. When it’s cold and wet, the fungus will travel through the air currents onto your pumpkin.

Powdery mildew thrives in climates between 69-80F.

Temperatures consistently below 60F or above 100F will deactivate the fungus.

Over-fertilizing can also contribute to mildew, especially with nitrogen focused compounds.

This is why you should always UNDER fertilize than over.

Poor air circulation is another huge contributor to powdery mildew.

When your pumpkins have poor air circulation from the dense leaves and vines, this can block the airflow that will then make your pumpkin favorable to fungal diseases- not just powdery mildew.

Shady areas with low sunlight harbor bacteria and fungus because there’s no sun to kill them and evaporate the water.

Pumpkins are ideal for this scenario, so it’s no surprise that powdery mildew takes its course on pumpkins and covers their leaves.

Prune damaged leaves

Leaves that have become damaged should be pruned off your plant immediately. This will help stop the infestation.

Plus, the damaged plants are no good for the pumpkin as it’ll attract pests who’ll feed on them. So prune them off.

Check for any foliage for damaged leaves and prune them off with a pair of garden gloves.

Next check for any vines that have been damaged. Trim them off also. Be ruthless.

Although you feel bad for cutting up your pumpkin, you’re doing it a favor by getting rid of the mildew.

Cut off any leaves that have started to turn white, yellow, or brown. Cut off any leaves with the visible white spores. It doesn’t matter if it’s partially colored or not, cut the whole thing off.

Disinfect the pruner by placing it in a solution of rubbing alcohol for a few minutes after you’re done. This will help prevent the spores from getting onto your other plants.

Additionally, check for vines that are witling, damaged leaves, yellow spots on the plant, and stunted growth.

If you’re growing a patch of pumpkins and a few plants seem smaller in size, there may be a fungal problem.

This is a critical step to stop powdery mildew for good.

Spend time doing this and don’t skip it. You’ll be surprised to see if your efforts are working or not. Scale your efforts accordingly.

Tidy up the pumpkin surroundings

Clean up the area around your pumpkin- this includes the soil, mulch, and fallen leaves or debris cluttering up the place.

These may have the same fungal virus as the leaves themselves, which can reinfect your plant the fungal spores. You should consider the soil around the stem of the plant to be infected and treat it as such.

Any other mulch, weeds, or neighboring plants should all be inspected and removed if needed. Treat it like a pest infestation. You need to be careful about the microscopic spores that you can’t see. They flow in the air currents, so they can be everywhere surrounding your pumpkin.

Sterilize all gloves, pruners, shears, garden spades, etc. before and after use so you don’t move the spores around. Just use straight 70% or higher rubbing alcohol and soak it for a few minutes to clean them.

Some people will use an organic or natural insecticidal soap spray in the soil around the plant.

This may be a possible option for you if you suspect that there are spores in the soil that’s causing the powdery mildew infestation.

Since the spores stick to the surfaces where they get air exchange, moisture, and partial light, they’re easy to spray down and eradicate.

You can even use a mild solution of rubbing alcohol that’s been diluted with water. A mixture of bleach and water also works, but you need to dilute it properly.

Avoid overfertilizing

Excess fertilizer, especially ones with high nitrogen (N) compounds, will lead to powdery mildew and all sorts of other problems with your plants.

Although many beginners think that fertilizer is a good thing and overdoing it will result in larger blooms, this is a terrible fallacy.

Always use as directed, perhaps even less than the suggested dosage when you’re in doubt.

Sometimes, less is (a lot) more. Use a soil tester to see where your soil currently stands.

You may find that you don’t even need any additional fertilizer or soil amendments/enhancers.

A high-quality soil tester will provide you readings of your soil’s conditions, so you have a good idea of what your soil has and what it doesn’t.

This will let you know if you even need to add that extra dose of plant food or not and helps prevent overdosing with nutrient-rich compounds that are unnecessary.

You’ll just end up attracting pests and more viral, fungal, or bacterial problems to your cucurbits.

If you need to use a fertilizer, use a slow-release capsule to prevent over-fertilizing.

Pumpkins and other cucurbits are susceptible to this disease.

Continue removing all signs of mildew by pruning them off, plant in full sun, and don’t over-fertilize.

Don’t overwater

Similar to avoiding excess plant fertilizers, you should also avoid excess watering.

Poor draining soil blocked waterways or just trapped moisture all allow for the growth of fungus.

Only water as much as you need to or use drip irrigation. Ensure that all water drains properly and there are no dead zones where water gets stuck in place.

Stagnant water will lead to a variety of pest problems like mosquitoes and add to humidity levels at the soil level around your pumpkin.

Provide good air exchange

With the dense leaves of pumpkin, it’s no wonder that the white fuzz grows so quickly on it.

You’ll want to provide plenty of air circulation by pruning off dense foliage where you think air gets trapped.

Some hardcore growers will add outdoor air circulators to move the air around.

But for casual people, simply pruning and tying leaves to stakes to ensure there’s no trapped moisture should be enough.

You can use stakes throughout your vines and tie them up to tidy them to prevent entanglement. Keep it neat to encourage proper air circulation.

Provide adequate spacing

Simply providing enough space between your pumpkin rows will help prevent the spread of the powdery mildew.

Plant them far apart as much as you can. Not only does this reduce the possibility of the fungus, but it also gives each pumpkin ample space to grow and not compete with neighboring plants.

Space the hills at least a nice 8 feet apart from each other so they can grow and maximize yield.

Remember that their vines need a lot of space. If you don’t have the horizontal space or you have a tiny garden, consider growing vertically using a plant support trellis.

Spray neem oil

Horticultural oils can be very effective against fungus on pumpkins.
Horticultural oils can be very effective against fungus on pumpkins.

Neem oil can be an effective essential oil to kill the fungus.

You can buy a bottle of concentrated neem oil and dilute it with water to make a powerful DIY fungicide for powdery mildew. There are multiple recipes out there for proper dilution, such as this one and this one.

Adjust the concentration as needed for your situation. Note that neem oil burns plants when you use it during hot weather.

So only spray at dawn or dusk- never in the afternoon. You should also wash off any excess neem oil because your plants may overheat from the residues. Use as directed.

Neem oil makes an excellent, organic way to control powdery mildew.

Always test on a single leaf before using it on the whole plant. If you notice damage, use less oil or use more water.

Use jojoba oil

Jojoba oil is a cold-pressed natural oil that’s commonly sold as an unrefined moisturizer.

It’s been reported to help eliminate powdery mildew, but I have no confirmation of this working. If you happen to have some handy, why not give it a try?

Spray some on the powder and see if it clears up. Of course, test it on a single leaf first before you apply it to the entire plant.

Sprinkle baking soda

Baking soda has 1000 uses and killing powdery mildew is just one of them. Mix some baking soda with water and spray directly onto the white leaves.

The alkaline mixture helps eradicate the fungal spores and protects your plant against future infestation. You can also mix a few drops of horizontal oil to enhance the effect.

The ratios vary, but typically a single tablespoon of baking soda to a gallon of water should be enough. Test on a single part of your plant before using it on the whole thing.

Note that baking soda doesn’t go away easily. It can build up in the soil and leech nutrients like calcium and magnesium as well as iron.

So you should watch out for any visible white buildup in the dirt, especially if you have dry climates or drip irrigation.

Use milk

Believe it or not, milk works as an effective mildew eliminator.

You can just use any generic brand of milk and dilute it with water.

Use equal parts water and milk (1:1) and then spray it on your mildew infested pumpkin leaves. That’s all you need. The milk reacts with the fungus and kills it.

Repeat this once or twice weekly until the fungus is gone. Be sure to get the vines and both sides of the leaves.

Fresh milk can also be diluted to make extra applications as a DIY fungicide. Milk is said to react with sunlight and produce a protectant against any fungal infections on plants.

Always test on a single portion first.

Rotate your crops

Don’t underestimate the power of crop rotation. This is necessary after you’ve had a case of powdery mildew because the fungus can live in the soil, even after you think you’ve cleared it.

The fungus will just enter a dormant state until the conditions give rise to another infestation of your cucurbits. However, this is rare.

Crop rotation can help prevent future mildew outbreaks by moving your plants around and placing a variety that’s not susceptible to powdery mildew to replace your pumpkin. Move the pumpkin to another location.

Check your plants often

When you’re trying to get rid of the powdery mildew, don’t forget to inspect your pumpkin plants weekly.

Whenever you water your plants is a good time to see what’s happening with your leaves. Look for signs of mildew on a schedule and see if it’s disappearing or getting worse.

You can also check neighboring plants to see if the fungal problem has landed on those leaves also. If so, you should start a plan of action right away so that you can kill the mildew before it takes over additional plants.

Again, the easiest way to spot powdery mildew is the small white specks of mold that grow on the leaves. Check both sides of the leaves for mildew.

You can use a magnifying glass to help (or just use your phone’s camera and zoom in on the plant)

How do you prevent powdery mildew?

Stopping the infestation from happening is always ideal.

There are some simple steps you can take at home to prevent powdery mildew from ever eating up your cucurbits.

Here’s a list of some of the most effective prevention techniques:

  • Space your pumpkins apart with good distance
  • Prune your leaves regularly on a schedule
  • Reduce the number of shady areas from leaf coverage
  • Establish good airflow between all dense foliage
  • Irrigate at the base of the plant- not the leaves (don’t water leaves)
  • Ensure good water drainage from your pumpkin plot
  • Use an outdoor air calculator to remove excess humidity
  • Don’t overwater or overfertilize
  • Plant mildew-resistant pumpkin varieties
  • Consider growing pumpkins vertically up a trellis
  • Remove all weeds and competing plants
  • Plant in full sun

Use copper sprays

Copper is very effective against powdery mildew as a fungicide.

Multiple sprays use copper as an active ingredient to eliminate powdery mildew. Use as directed. Wear proper PPE. Buy organic copper sprays if possible.

Apply sulfur

You can use sulfur to prevent future outbreaks of powdery mildew. It’s been a long proven effective remedy against stopping the mildew before it breaks out.

There are a few things to keep in mind before you use it:

  • Sulfur must be used before the mildew infects your pumpkin
  • Only use it when outdoor temperatures are cool (under 85F)
  • Avoid using oils

You can find pure, organic sulfur at specialty stores and greeneries. Use as directed.

Use a horticultural oil

Horticultural oils can be very effective against fungus on pumpkins.
Horticultural oils can be very effective against fungus on pumpkins.

Horticultural oils are excellent for pest, viral, and bacterial control.

Most of them are natural and you can find them widely available at hardware stores. Do your own research and find one suitable for pumpkins.

Read some reviews and pick out a good one. Use as directed.

When combined with a treatment plan and regularly pruning your cucurbit, it can be an effective way to get rid of powdery mildew naturally without using dangerous compounds.

Grow mildew resistant cultivars of pumpkin

There are some varieties of pumpkin that are known for their resistance to powdery mildew.

Some of the most popular strains are Magician, Aladdin, Hobbit, Gladiator, ScareCrow, Pure Gold, Rival, Trophy, and Gold Dust. These strains can help you withstand powdery mildew breakouts in the future.

Although no strain’s 100% resistant to this fungus, these strains can help reduce the chance of the outbreak.

Don’t be fooled by the term “resistant.” That doesn’t mean they can’t get powdery mildew. “Resistant” simply means that these strains are less susceptible to it.

But if you provide poor airflow with high humidity and lots of shade, the spores can just blow in from your neighbors.

Choosing the right fungicide for powdery mildew

If you have a severe powdery mildew problem, you can consider using fungicides to kill and control the problem.

This particular disease has evolved to the point where it can resist most compounds used against them, so the best approach is to alternate between at least two different fungicides.

This doesn’t just mean going out and buying two different brands.

You need to look at the FRAC code on each package and use different codes. The most variety of fungicides you use, the higher chance of eliminating the fungus you’ll have.

Using a single FRAC code will just lead to resistance and a waste of money.

Don’t be cheap on this when you’re at the store. Think about this way: buying a single container will be useless, so that’s wasted money.

Buying two different containers will work, so that’s useful unless you only have a mild powdery mildew problem on your pumpkins.

Some gardeners even report using two different fungicides at the same time to treat powdery mildew.

You can consider doing that if there’s no reaction between them. Read the label and follow the directions.

Look for any of the following fungicides for best results:

  • Quinoxyfen
  • Difenoconazole
  • Metrafenone
  • Myclobutanil
  • Benzovindiflupyr (commonly bundled with difenoconazole)
  • Fluopyram
  • Tebuconazole

You should only use organic or natural DIY home remedies first.

Only resort to these compounds when you have to. They also harm the environment and may affect other plants for pollinators in your garden.

So minimizing usage should be a priority.

Further reading

Here are some references you may find useful:

Did you get rid of the powdery mildew on your pumpkin?

White pumpkins free of powdery mildew.
Now you can enjoy powdery mildew free pumpkins.

You should have all the knowledge you need to get rid of the mildew from your pumpkin.

Even though the powder is ugly, it’s rarely enough to do permanent damage to established cucurbits.

With some TLC, you should be able to control and eliminate the fungus with some basic remedies at home.

Do you have any questions? Or tips to give to other readers? Post a comment and let us know.

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