What's the best fungicide for root rot?
Written by
Tina Carter
Reviewed by
Prof. Charles Hartman, Ph.D.Choosing the optimal fungicide to use for root rot is complicated by the infection's severity and the type of plant you are dealing with. I was able to salvage a client's collection of orchids with hydrogen peroxide and a landscaper's boxwood shrub suffered Buxus Blight Fighter. The important thing to remember with any treatment is to match the treatment option to the pathogen, what may work for Pythium will not be effective against Armillaria.
Hydrogen Peroxide
- Dilution: 1:4 ratio (3% solution to water)
- Use: Mild infections, pre-repotting root soaks
- Limitation: Doesn't treat advanced Phytophthora
Buxus Blight Fungus Fighter
- Targets: Phytophthora, Calonectria species
- Use: Shrubs/trees, apply every 14 days
- Limitation: Overuse harms beneficial soil microbes
Neem Oil
- Application: Soil drench (2 tbsp per gallon)
- Use: Prevents fungus gnats and secondary molds
- Limitation: Weak against established infections
Copper-Based Fungicides
- Strength: Eradicates severe Rhizoctonia outbreaks
- Use: Outdoor plants only, apply at dawn/dusk
- Warning: Toxic to aquatic life
I use copper fungicides only in desperate cases. I was once called to help a client with a rose bush suffering from Rhizoctonia, and despite applying the copper fungicide three times, the fish in her pond died due to copper runoff. Now, I only use it during the dry season, and I replace soil to limit the toxicity and overall impact on the environment.
Neem oil has become my first line of defense for potted plants inside my home. I gave my fiddle leaf fig weekly soil drenches with neem oil to keep fungus gnats away all growing season for six months. Using thorn for even more thorough management, you give it to the natural behavior of a sticky trap. Neem oil maintains prevention, hydrogen peroxide maintains remedy.
Read the full article: How to Treat Root Rot: 7 Essential Steps to Save Your Plants
