Identifying and Treating White Spots On Pumpkin Leaves

white spots on pumpkin leaves

White spots on pumpkin leaves can be very disheartening. These ashy, pale patches are most likely a fungus called powdery mildew that attacks many different plants, including pumpkins. Leaving it untreated could result in slowing down your pumpkin patch’s development or wiping out your crop completely. Today we’ll share the best ways to treat and prevent white spots on pumpkin leaves. We’ll look at using baking soda, milk, potassium bicarbonate and neem oil to remove mildew, and providing the right levels of air flow, water and fertilizer to prevent it returning. Helping you to grow healthier, more fruitful pumpkin plants!


white spots on pumpkin leaves

What Causes White Spots On Pumpkin Leaves?

Whether you’re growing pumpkins for the first time, or you’ve done it a dozen times before, few of us are immune from white spots gradually encroaching on the leaves towards the end of the season. Your plants are likely infected with a common fungal disease called powdery mildew. This is an extremely widespread problem in a whole range of plants. Luckily, it’s almost always a treatable problem.

Are White Spots on Pumpkin Leaves Powdery Mildew?

Powdery mildew is a fungus that can affect a wide variety of plants. It typically appears as white or light grey spots on leaves but can also grow on stems, flowers, and fruit. Left untreated, it will spread so that it eventually covers most of the leaves, and new growth is particularly vulnerable to powdery mildew.

Not only are the white spots on your pumpkin leaves unsightly, powdery mildew can seriously damage your pumpkin plants by depriving them of water and nutrients, causing them to grow slower and bloom less. This fungus usually occurs in late spring or early summer in climates with warm days and cool evenings, low sunlight, and high humidity.

Will Powdery Mildew Kill My Pumpkin Plants?

Although powdery mildew probably won’t kill established pumpkin plants, it can do a great deal of damage to young plants and developing fruit.

How To Treat White Spots on Pumpkin Leaves

If your pumpkin leaves have white patches, you’ll need to take measures immediately. If left untreated, it will spread, resulting in a severe infection, which can mean a lower yield and less flavorful fruit.

Getting Rid of the Fungus

Before you treat the plant, remove the leaves, vines, stems, or fruit with mildew spots and discard them. Sterilize pruning shears before and after use to prevent further mildew spread, and wash your hands with soap and water after touching the infected pumpkin plant. There are several home remedies to treat an existing powdery mildew infection.

  • baking soda
  • milk
  • potassium bicarbonate
  • neem oil

Baking soda

Combine one tablespoon of baking soda and ½ teaspoon of non-detergent liquid soap with one gallon of water and spray the affected leaves and other affected areas of the pumpkin plant. Spray liberally because this solution will only kill the fungus it comes in contact with.

However, baking soda can burn your plants if it accumulates, causing nutrient deficiencies in the soil and leading to slower growth.


Mix 40% milk and 60% water in a spray bottle and spray liberally on the affected parts of the plant every ten to 14 days.

Potassium Bicarbonate

Combine one tablespoon of potassium bicarbonate and ½ a teaspoon of non-detergent liquid soap with one gallon of water and spray all affected areas generously. This solution may work better on pumpkin plants that have existing infections.

Neem Oil

Neem oil is an essential oil that can be diluted with water for powdery mildew. However, it can burn the plant in hot weather, so only apply to the leaves at dusk when the plant is in the shade.

Always test it on one leaf before applying the solution to the whole plant and adjust the concentration as needed.

How To Prevent White Spots On Pumpkin Leaves

There are several ways you can reduce your pumpkin plant’s risk of getting powdery mildew.

Planting to Avoid Powdery Mildew

When planting your pumpkin patch, choose a spot where they’ll get full sun. Plant them far enough apart to allow for good air circulation. They should be at least six to ten feet apart so the vines can spread out and the plants aren’t growing on top of each other. Another alternative is to grow your pumpkin vines over a trellis. This can work well with smaller varieties

Not only does this reduce the chances of your pumpkins getting or spreading powdery mildew, but it also gives them ample room to grow bigger fruit. If you don’t have much space, consider using a trellis and training them to grow vertically.

  • allow air circulation
  • avoid over watering
  • don’t over fertilize
  • check your plants regularly

Allow Air Circulation

Pumpkins have very dense leaves, which can trap air and moisture. Good air circulation prevents condensation on the leaves and reduces the growth of powdery mildew, other fungal infections, and rot. As your pumpkin plants grow, prune off dense foliage to keep the air circulating.

Avoid Overwatering

Poor draining soil and trapped moisture is another way to encourage fungal growth. Only water as much as needed. Standing water will increase the humidity levels in the soil and attract other pests as well.

Water the soil at the base of the plant to avoid moisture on the foliage, and never overwater to ensure good water drainage.

Don’t Over Fertilize

It’s also crucial to not overfertilize your pumpkin plants. Use a soil tester before planting to get an idea of the soil’s nutrient balance before adding fertilizer. If you use a fertilizer, choose one that releases slowly over time and avoid those with high nitrogen content.

Check Your Pumpkin Plants Regularly

Inspecting your plant’s leaves weekly or whenever you water will help prevent powdery mildew from infecting your plants and spreading. Don’t forget to check both sides of the leaves.

How Does Powdery Mildew Spread?

Powdery mildew spores are usually carried by the wind into your garden when it’s warm and dry. However, if you had an outbreak in the past, fungus can survive in nearby vegetative material or leaf piles, so it’s important to get rid of old infected plants and debris. Once a spore lands on a plant, it will quickly develop a new infection.

Avoiding and Curing White Spots on Pumpkin Leaves

For those planning a pumpkin patch, make sure to give your plants plenty of space and sunshine. If you have an existing crop, the best way to avoid powdery mildew is to check your plants often and if you see white spots, start treatment early.

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