How to Stop Fungus on Seed Potatoes


Even a seed potato purchased from a reputable nursery or garden store may be infected with fungus spores. When the seed potato is planted, the warm soil and moisture can cause these spores to develop into any one of several potato diseases, including black rot. Stop fungus on seed potatoes by sterilizing your seed potatoes before you plant them. Proper sterilization doesn't just help your current potatoes, but also future potato generations since fungus on the potato can linger in the soil long after the infected potato is uprooted.

Borax (Sodium Borate)

Step 1

Pour 1/3 cup borax into a gallon-sized plastic bucket. Borax is available from most general grocery stores.

Step 2

Add 1/2 gallon of fresh water into the bucket.

Step 3

Use a spoon to mix the bucket's contents thoroughly until the borax is dissolved.

Step 4

Put your seed potatoes into the solution and let them soak for 10 to 15 minutes. After this time is up, remove the potatoes and plant them immediately. Borax effectively sterilizes seed potatoes and kills fungi, according to Clemson University.

Tips and Warnings

  • Avoid planting your potatoes near any of your garden's tomato plants. The same diseases affect both species, according to North Dakota State University.

Things You'll Need

  • Borax powder
  • Plastic gallon-sized bucket or container
  • 1/2 gallon water
  • Spoon
  • Seed potatoes


  • "How to Grow Potatoes: A Practical Gardening Guide for Great Results"; Richard Bird; 2009
  • Clemson Cooperative Extension: Irish & Sweet Potato Diseases
  • North Dakota State University: Management of Potato Diseases

Who Can Help

  • Ohio State University: Growing Potatoes
Keywords: seed potato fungus, kill potato fungus, sterilize seed potatoes

About this Author

Josh Duvauchelle is an editor and journalist with more than 10 years' experience. His work has appeared in various magazines, including "Honolulu Magazine," which has more paid subscribers than any other magazine in Hawaii. He graduated with honors from Trinity Western University, holding a Bachelor of Arts in professional communications, and earned a certificate in applied leadership and public affairs from the Laurentian Leadership Centre.