Can You Wash Off Powdery Mildew After Harvest?

Powdery mildew is one of the most common blights that crops, houseplants, and garden flowers can develop, and it can be pretty unsightly and concerning if you spot it. However, white powdery mildew is not the end of your garden, and if you catch it early, you can treat it quickly and leave your harvest in good shape for consumption. 

You can wash off powdery mildew after harvest with baking soda, vinegar, or hydrogen peroxide. Powdery mildew is not harmful when ingested unless you have an allergy, but removing the spores from your harvest and crops is still beneficial.

Let’s discuss the details and discuss removing powdery mildew from your crops and harvest. I’ll tell you about the health risks of consuming powdery mildew, how to eliminate it from your harvest, and touch on some of the characteristics of this garden fungus. 

Can You Eat Powdery Mildew?

You can eat powdery mildew, but you shouldn’t. Powdery mildew is not toxic to humans but may affect people with mildew allergies. Those with allergies to this mildew may experience digestive or respiratory issues after consuming it, so it is best to avoid consuming powdery mildew.

Powdery mildew is not toxic when ingested unless you are already sensitive to it. You probably won’t even notice if you accidentally consume a bit of powdery mildew as long as you are not allergic to it. 

On the other hand, you will likely notice classic allergy symptoms such as sneezing, a runny nose, itchy eyes, or coughing if you are allergic to this mildew. 

It’s best to be safe rather than sorry when dealing with powdery mildew – some people may have undiagnosed allergies, so avoid taking a bite out of your crops if they’re affected by this issue. Instead, wash off the fungus as soon as you spot it. 

Does Powdery Mildew Harm Plants? 

Powdery mildew is harmful to plants – it is a surface infection that prohibits plants from respiring. Plants with powdery mildew will also bear a smaller harvest, and the crop will not taste very good.  

White powdery mildew blocks a plant’s “pores,” where water and oxygen exit the plant through the leaves. When the infestation is bad enough, your plant will have difficulty “breathing,” and you’ll notice stunted growth and a significantly smaller harvest. 

If you don’t wash away the mildew, your plant may die. 

This process can also affect the development and taste of your harvested plants. Plants such as tomatoes and squash will taste more bitter and grainy than uninfected plants of the same variety. 

So, powdery mildew harms your plants and makes your harvest go sour. That’s why it is critical to eliminate it as soon as you notice it on your harvested or unharvested crops.

How Does Powdery Mildew Infect a Garden? 

Powdery mildew infects a garden when its spores find their way onto your crops. Like most fungi, powdery mildew releases spores that the wind carries. These spores may be difficult to eradicate since they may lay dormant for a season, then come back when the weather warms up. 

Powdery mildew spreads its spores via the air. This mildew can only survive and mature when it is on a live plant, so it will congregate on the stems and leaves of crops. 

However, powdery mildew only thrives on some plant varieties. Most of these plants have high water contents, giving the fungus a damp environment to propagate in. Some of the most common garden plants that powdery mildew grows on include: 

  • Tomatoes, eggplant, and peppers (all within the nightshade family)
  • Beans and peas
  • Cucumbers and squash
  • Leafy vegetables such as lettuce and chard
  • Carrots and potatoes

These plants are desirable to powdery mildew, and their leaf shapes and textures allow the spores to cling tightly to the plant. However, this mildew thrives when the environmental humidity is high, so it most often crops up during fall and spring showers. 

Powdery mildew cannot thrive in high heat conditions, so it will often go dormant during the peak of summertime, only to return in the fall. 

Methods for Washing Off Powdery Mildew After Harvest

Now that you know how powdery mildew has ended up on your crop and its risks, let’s talk about how you can wash it away. 

When most people see powdery mildew, their first instinct is to wash it off with a hose. While the hose may displace some of the mildew’s spores, it will only push them into the soil and infect it, ensuring that the mildew returns every season. 

The only way to eradicate powdery mildew is to use a fungicide. 

However, don’t fret – you don’t have to use harsh, toxic chemicals to eliminate your mildew issue. You likely already have some household-safe fungicides lying around. Let’s look at what they are and how you can use them to wash off your harvest (and your plants). 

Use a Hydrogen Peroxide Dip

Hydrogen peroxide is one of the best treatments for any fungal infection in plants. Peroxide damages the powdery mildew’s cells, preventing it from maturing and spreading. However, if you use too much peroxide, you may also damage your plants’ cells.

To use hydrogen peroxide dip without risking damaging your crops or plants, you need to dilute it. If you are using 3% hydrogen peroxide, add one tablespoon of peroxide (15 ml) per cup (240 ml) of water. 

Here’s how to dip your harvest: 

  1. Place your solution in a container large enough to hold your entire harvest. 
  2. Then, place your crops in the solution and wait a minute or two to allow the peroxide to neutralize the mildew thoroughly. 
  3. After a brief wait, swirl your harvest in the solution to “shake off” the mildew.
  4. Pull your goods out of the container and dry them on a clean towel. 

You can use this same process with live plants to eliminate powdery mold, but it can be tricky to uproot the plant and dip it. Another method for rooted plants is generously spraying this same solution onto the mildewy areas. 

Spray the Harvest or Plants With a Baking Soda and Soap Solution

Baking soda and soap change the pH wherever you put them, which is enough to eliminate powdery mildew. The soap is also slimy enough to coat spores, preventing air from getting to them. These features make a baking soda and sop solution one of the best methods for preventing the spread of powdery mildew. 

Mix one tablespoon (28 grams) baking soda and ½ teaspoon (7.5 grams) castile soap into one gallon of water to make this mildew-fighting concoction. Then, dip your harvest in the solution or spray it on. If you plan on consuming your crop, you may want to rinse off the soap and baking soda before you serve it. 

That said, this solution is food-safe, so don’t worry if you leave some traces of the soap. 

Treat the Crop With Milk

Milk is one of the most food-safe fungicides available, so it’s perfect for washing off your edible harvest. The enzymes in milk (those used to make cheese and yogurt) are active enough to eat and kill fungi such as powdery mildew. 

To use it, dip or spray some cow’s milk onto your plants or harvest and watch the mildew fade away. Milk is also suitable for spraying soil around your garden to eliminate dormant mildew spores. However, be prepared for a sour smell on sunny days!

Burn the Powdery Mildew With Vinegar

Vinegar is one of those cure-alls that can prevent pests and clean out fungi such as powdery mildew. It works because it is so acidic that it damages the fragile cells of the fungi, killing and neutralizing them on contact. 

When using vinegar on plants, I recommend using apple cider vinegar. Apple cider vinegar is gentler on a harvest than white vinegar and doesn’t taste as bitter.

Here’s how to use it: 

  1. Mix 2 tablespoons (30 ml) of vinegar with one gallon of water (3.8 liters) in a large container. 
  2. Dip your harvest in the solution and allow it to soak for a minute or two, which will ensure that the mildew is all dead. 
  3. Then, swirl your crop around in the solution to displace any spores or dead mildew. 
  4. Remove your harvest and lay it on a towel to dry. 

Like the peroxide solution, you can use this method as a dip or spray for live plants. 

Final Thoughts

White powdery mildew may not be toxic to humans, but it can affect the taste and quality of your crops. You can wash it off your harvest using peroxide, vinegar, soap, baking soda, milk, or vinegar. You can also use milk, vinegar, or hydrogen peroxide to completely eliminate powdery mildew from your plants so that you don’t have to worry about it getting to your precious crop again. 

If you want to learn more about harvesting and storing your fruits and vegetables, you can read my other article here: How to Harvest and Store Your Fruits and Vegetables

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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