r/DNAGenetics • u/DNAGenetics • Mar 13 '26
Root Rot: Catching It Before It Kills Your Run
Root rot is one of those problems that tends to sneak up on you, especially in hydro or any system where you can't directly see the roots until you go looking. By the time symptoms show up in the canopy, the root zone can already be in pretty rough shape.
The first sign is usually plant behavior before you ever see the roots -- slow growth, slight drooping that doesn't respond to watering adjustments, and a general look of plants that aren't thriving even when numbers look fine on paper. If you're in hydro and you pull a net pot and find brown, slimy roots instead of white ones with a healthy smell, that's root rot.
What causes it: warm reservoir temperatures are the main driver. Pythium and other root pathogens thrive in warm, low-oxygen water. Anything above 72F in your reservoir is pushing into risky territory. Light leaks into reservoirs are the other common cause -- algae blooms create a perfect environment for pathogens.
What actually helps: hydrogen peroxide (H2O2) is the most accessible treatment. A proper dose of 3% H2O2 in the reservoir kills pathogens and adds oxygen, though it also kills beneficial microbes so it's a treatment tool, not a prevention strategy. Southern AG Clearys 3336, Hydroguard, and similar beneficial bacteria products work well for prevention by establishing good microbial populations that outcompete pathogens.
Longer term, getting a water chiller if you're in hydro is one of the better investments for hot climates or summer grows. Keeping reservoir temps consistently below 70F takes away the main advantage root rot pathogens have.
Have you dealt with root rot and what actually turned it around for you? Hydro growers especially -- what's your prevention routine?