How to Make Rhubarb Spray Pesticide

Learning how to make rhubarb spray is a great way to add another DIY pesticide or insecticide to your gardening arsenal. Not only does it give you a way to make the most of your plants if you grow rhubarb, making rhubarb spray is an easy way to keep an organic, affordable pesticide on hand for dealing with the inevitable aphid infestations and mildew issues that gardening brings.

DIY insecticide rhubarb spray

How to Make Rhubarb Spray

What You’ll Need

  • 1/2 to 1/3 cup rhubarb leaves (preferably organic)
  • 3 quarts water
  • Large pot
  • Blender (optional)
  • Cheesecloth or sieve
  • Pump spray bottle
  • Dish soap (optional)

What You’ll Do

  1. Cut or tear the rhubarb leaves into small pieces. If you’re using rhubarb leaves that have been sprayed with pesticides and you want to reuse them for composting, thoroughly wash the leaves before using them.
  2. Place the leaves in a large pot with the water, then bring the water to a rolling boil.
  3. Turn off the heat, then steep the leaves for at least 2 hours. The longer you steep the leaves, the better, so you can even let them steep overnight if you like.
  4. Optional: Put leaves in blender and pulse until thoroughly blended.
  5. Strain mixture through cheesecloth or sieve.
  6. Optional: Gently mix with 6 tsps liquid dish soap.
  7. Pour into a spray bottle.
  8. At first sign of mildew disease or aphid infestation, spray affected plants thoroughly (both the tops and bottoms of leaves).
    WARNING: If you can avoid spraying the portions of plants that you intend to eat, do so. If you cannot, be sure to thoroughly wash any plants you spray before ingesting. You may want to avoid using on plants that have “nooks and crannies” that could make them difficult to clean (such as broccoli and cauliflower).


Rhubarb spray can be frozen for future use, kept in the fridge, or made to order whenever a new batch is needed. If storing in the refrigerator, remember to give it a good sniff before use to make sure the mixture is still usable.

Because rhubarb spray can be quite toxic due to the high concentration of oxalic acid, be sure to label the bottle or find some other way to ensure it won’t accidentally be used or ingested.

Using Rhubarb Spray

Rhubarb spray is good for dealing with mildew issues (such as powdery mildew) and aphid infestations. When using your spray, remember to:

  • Spray affected plants every other day until the aphid infestation or mildew problem appears to be under control.
  • Spray at night or as night approaches, since the spray can affect daytime pollinators like bees and butterflies.
  • Thoroughly wash any foods sprayed, since the spray isn’t just toxic for pest insects, it’s toxic for humans too.

Looking for other ways to deal with common garden problems and pests? Check out this article on homemade bug sprays or this one on homemade insecticidal soaps. Or, consider growing more plants that repel insects.

Images thanks to Barb Crawford!

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