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How to Identify and Treat 5 Pumpkin Diseases

There’s no other fruit as synonymous with a season as pumpkin is to autumn. If you relish its flavor in your coffee or Thanksgiving pie, you might want to consider growing your pumpkins.

Pumpkins growing on vines. Being educated about pumpkin diseases is part of proper pumpkin care.

They’re easy to grow if you know how to prevent and treat common pumpkin diseases. This article will help you do both.

Read on to learn more so you can enjoy pumpkins from your backyard patch next year.


Pumpkin Diseases and Treatments

From the time you plant seeds, it takes 120 days until pumpkins are ready to harvest. During that time, you might encounter one or more pumpkin diseases.

Here are some you should know about. Early treatment can mean the difference between saving and losing your pumpkin patch!

Powdery Mildew

Powdering mildew on pumpkin leaves.

How to Identify Powdery Mildew

Powdery mildew is a type of fungus. It’s prevalent during humid summers and affects plants with young fruit.

White spores develop on the leaves and vines of the plant. It may seem surface deep, but this particular pumpkin disease will start a chain reaction.

Leaves turn yellow then dark brown. If left untreated they’ll wither and eventually die. This exposes young pumpkins to more sun causing their rinds to deteriorate.

Stunted growth occurs in less extreme cases. This can result in smaller pumpkins that may not fully ripen.

Treatment of Powdery Mildew

Early treatment of powdery mildew is essential as spores travel through the air and can affect other plants. Rain also plays a factor as droplets can spread the spores from one leaf to another.

If you notice yellow leaves on your plants, remove them immediately. If the mildew is widespread, it’s best to use a copper fungicide or a sulfur fungicide and apply it with a handheld garden sprayer.

Downy Mildew

Downy mildew on pumpkin leaves.

How to Identify Downy Mildew

Downy mildew is a fungus that thrives in extreme, continuous humidity. This pumpkin disease also affects the leaves of the plant. Yellow splotches emerge on both the upper and lower sides of older leaves. If left untreated they can spread to younger ones as well.

White, fuzzy spores appear on the underside of the leaves with the spores eventually turning brown. Lack of treatment can result in leaf loss. In severe cases, the stem of the plant becomes discolored.

The quality of the pumpkins from affected patches is usually poor and they’re often smaller.

Treatment of Downy Mildew

The wind can spread downy mildew spores across your pumpkin patch. Early detection and treatment are key to preventing this.

Treatment involves using fungicides containing chlorothalonil and mancozeb, such as Bonide Mancozeb.

Bacterial Leaf Spot (BLS)

Leaf spot on a plant.

How to Identify BLS

This is a bacterial seed-borne pumpkin disease. It first appears on the underside of the plant’s leaves as small dots that merge over time. The upper side of the leaf will eventually become yellow which usually signals a widespread infection.

If this is the case, you’ll also notice signs of this pumpkin disease on your fruit. It will appear as circular, sunken spots that enlarge over time.

This exposes the fruit to secondary microorganisms that cause rotting. Fruit can also appear fine but rotting can occur after harvesting.

Treatment of BLS

Before planting, treat your seeds with sodium hypochlorite, dry heat, or hot water. This will not eliminate the bacteria but significantly reduce them.

You can avoid infected seeds by buying pumpkin seeds from a reputable seed retailer like Hoss Tools, one of our favorites! 

But if you do encounter this insidious pumpkin disease, you can treat it with a copper fungicide.

Gummy Stem Blight

A pumpkin on the vine.

How to Identify Gummy Stem Blight

A gummy is the last thing you would associate with pumpkin disease. But its appearance is what gives this blight its unusual name.

It appears as small golden brown spheres on the plant’s stems that can be easily mistaken for drops of tree sap.

A closer look will reveal black specks or fungal spots. These eventually darken and are often referred to as black rot.

This blight thrives in moderately warm temperatures with humid, moist conditions.

Treatment of Gummy Stem Blight

Gummy Stem Blight spreads via infected seeds and soil. Daconil Fungicide can prevent, eliminate, and control this type of blight.

Use it on the entire plant when conditions become humid and moist or when the blight first starts to appear.

Southern Blight

Black mold on a pumpkin.

How to Identify Southern Blight

Southern blight is a fungus that thrives in soil. It develops in temperatures as high as 75°F to 95°F, usually experienced in southern climates, hence its name.

It first appears as small spheres of white mold on the plant’s stems. Over time, the stems eventually turn brown. It attacks parts of the plant closest to the soil, including the fruit.

Treatment of Southern Blight

Plowing the top layer of the soil and adding fungicides before planting your seeds will help. But the key to avoiding Southern blight is maintaining the soil’s pH levels.

You can do this by using one of the pH testers in our article on the Top Ten pH Soil Testers we recommend.


Pumpkin Disease Control

Most of the pumpkin diseases in this article thrive in humid and moist conditions. You can inadvertently invite fungal diseases into your pumpkin patch by not being mindful of the frequency and method of watering your plants.

Our Pumpkin Watering Guide can help you create the right balance for your plants to flourish.


Eliminate Pumpkin Diseases and Preserve a Fall Staple

Pumpkins have become a staple for autumn. You can enjoy a slice of pie or spice up your coffee by growing your own pumpkin patch.

Pumpkins growing on a vine.

Having the upper hand on pumpkin diseases means you could try a new variety of pumpkin fruit each season.

Learn more about pumpkins by visiting our Pumpkin Plants page for blog posts as well as helpful growing and care guides.