White Spots on Pumpkin Leaves | Causes, Treatment and Prevention

Perhaps you’re trying to grow a giant pumpkin for the state fair. Or maybe you just want a jack o’lantern for Halloween. Regardless, the white spots appearing on your pumpkin leaves can’t be good for the overall health of your pumpkin.

So why are these white spots appearing on your pumpkin leaves? The white spots on your pumpkin leaves are most likely caused by powdery mildew. Powdery Mildew is a fungal disease that affects pumpkins as well as many other plants. If left untreated, it will slow down the growth of your pumpkin and could even kill the entire plant outright.

 Overall, this is a pretty bad fungal disease for your pumpkin plant and many other plants in your garden. However, there are ways to not only treat powdery mildew but also prevent it from infecting your plants in the first place.

Causes of Powdery Mildew

You cannot treat or prevent a disease unless you know what causes it first. So, what causes the white spots on pumpkin leaves? Powdery mildew is a name that is used to define a group of diseases that are caused by related fungi. It is caused by a very common leaf infecting disease.

Even though each of the fungi has a different host, the powdery grayish-white appearance is the same on leaves, flowers, and stems of different plants. The fungi specific to pumpkin leaves are known as Erysiphe Cichoracearum. It also affects vegetables such as lemons and lettuce and  also flowers such as dahlias and sunflowers.

The white powdery appearance is a result of a significant number of microscopic spores that are born in chains. These spores do not need water for them to germinate. Hence, they thrive in warm weather when the foliage is dry. New spores are also produced every three to fourteen days and are spread to other plants via the wind.

White Spots on Pumpkin leaves

The optimum environmental conditions for the development of powdery mildew include cool and humid nights accompanied by dry days. Such an influx in temperature causes the disease to spread very quickly. 

Other conditions that are favorable for the development of powdery mildew include humid conditions that have a temperature that ranges between 68 and 81 degrees Fahrenheit.


Overcrowding your plant space will also provide the powdery mildew spores excellent conditions for growth. Having good ventilation throughout your garden or greenhouse can reduce the spread of the powdery mildew fungus. However, if your garden is not ventilated properly, this will encourage the spread of the powdery mildew spores.

Another cause of powdery mildew is insufficient light. If your pumpkin leaves are exposed to excess shade, they will lack the amount of light that is necessary for the production and growth of buds. That is why powdery mildew favors the season between late summer through mid autumn since the cooler temperatures are more suitable for its growth.

If left untreated, the disease will cause the pumpkin leaves to turn yellow after which they will die and fall off. Additionally, the white spots on pumpkin leaves can progress further and lead to the exposure of the pumpkin fruits themselves to sunburn; yes pumpkins can get sunburn too. If this happens, your pumpkins will not grow as big and will look very unappealing.

How to Treat Powdery Mildew

There are many different methods that you can use to treat powdery mildew. The best methods are organic methods since they work better than chemicals. Also, always remember to coat the leaves liberally on both sides with your treatment solution. Reapply the treatment every week unless the products advise otherwise.

Pruning Your Pumpkin Vine

One of the methods that you can use to treat the powdery mildew is by removing the leaves that are already infected. When pruning, ensure that you place the diseased foliage in plastic bags. This will prevent the spread of spores to healthy plants.

Once you have removed the mulch, plant debris around the affected pumpkin plants. Ensure that you have checked the leaves from the surrounding plants. This will prevent your pumpkins from being affected again. Remember to sterilize the equipment that you use when pruning before and after use.

Neem Oil Method

Neem oil is made from the fruit and the seeds of the neem tree. It has the power to kill the powdery mildew within a day. The oil works by disrupting the metabolism of the plant as well as stopping the production of the spore. Neem Oil can even be found on Amazon.com by clicking here.

Since Neem oil is also a great insecticide, it will prevent the transmission of the spores by the bugs to your pumpkin leaves. Add 2.5 tablespoons of neem oil to a gallon of water and spray your plants every seven to fourteen days. Avoid spraying the flowers and buds. 

Milk Spray Method

Some studies have proven milk to be a more effective treatment for the white spots on pumpkin leaves than some fungicides. Fresh milk diluted to a 10 percent solution with water will remove the powdery mildew from pumpkin leaves. This solution works just as well as Sulfur and synthetic fungicide in most cases.

Scientists are yet to discover why milk works in treating powdery mildew. It is believed that the milk interacts with the sun and produces free radicals that are toxic to the fungus. Nevertheless, use one part milk and 8 parts water solution to eliminate the powdery mildew on your pumpkin leaves.

Baking Soda Method

There are already many uses for baking soda in your home. Now you have one more reason to stock it in your house. Baking soda is a very efficient remedy for powdery mildew. Just like milk, its effectiveness is not understood. However, it is believed that baking soda helps the pumpkin leaves produce a compound that defends against the powdery mildew.

For more effectiveness, use baking soda with horticultural oil. To make the treatment solution, add a tablespoon of baking soda to a gallon of water. Then add 2.5 tablespoons of horticultural oil. Test for phytotoxicity before spraying the solution on all your plants.

If you live in drought areas and only use drip irrigation, be cautious of using baking soda since it can build up in the soil. Concentrated amounts of bicarbonate in the soil can result in reduced levels of calcium and magnesium. It can also reduce the absorption of iron which can cause iron chlorosis.

Copper and Sulfur Fungicides

You can clear the white spots on pumpkin leaves with these two fungicides. Sulfur is very effective at treating and controlling powdery mildew. Its typically sold as a liquid or as dust. You can also add the product to sulfur vaporizers. You can purchase some sulfur fungicide on Amazon by clicking here.

Copper is also highly effective in treating powdery mildew. For both fungicides, ensure that you follow the instructions given precisely. Wear gloves, cover your face and eyes with a mask, and avoid inhaling the fumes. Copper Fungicide can be purchased on Amazon by clicking here.

Final Instructions

Remember, it is best to alternate between the methods that have been listed above. Studies show that one method used repetitively, organic or not, might allow the fungi organisms to be resistant. Therefore, spray the remedy every week but alternate between the choices listed. You should also wash your hands with soap and water after handling the infected plants.

Preventing Powdery Mildew

The most cost-effective way to deal with this fungus is preventing it from occurring in the first place. Powdery mildew thrives in conditions where the temperatures range between 50 and 65 degrees Fahrenheit as well as humidity ranging between 80 and 90 percent.

dery Mildew on Plant Leaf

Therefore, the ideal method of preventing powdery mildew is by avoiding environments where the temperatures are low and humidity is high. When it comes to planting, you can prevent the white spots on pumpkin leaves by spacing them properly as to not overcrowd them.

By ensuring you have good circulation around your plants, especially in a greenhouse, the humidity levels will stay low. Besides, crowding provides shade for plants which encourages the growth of fungi. In case of overcrowding, prune some of the leaves.

Also, since powdery mildew will not grow in high temperatures, give your plants access to direct sunlight. The sun’s direct rays will kill the spores before they spread. Moreover, try buying hybrid plants that are resistant to powdery mildew in order to prevent its growth.

Water the base of the plant and not the leaves. Water will not encourage the growth of powdery mildew but it will spread the spores. In case of infection, trim the infected areas and dispose of them accordingly, preferably by fire.


You no longer have to wonder what the white spots on pumpkin leaves are. As mentioned above, they are a result of fungi growing on plants. The fungi thrive in hot temperatures and humid regions. The fungi are also detrimental to the health of your pumpkin; therefore, the best course of action is to prevent its occurrence.

Otherwise, if powdery mildew appears on your plants, you can treat it and prevent it from spreading. Using milk, baking soda, and other fungicides that will help you manage the powdery mildew on your pumpkin leaves. Nevertheless, just be sure to examine your plants regularly.

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