Root Rot Starts with Wet Roots: Fix Irrigation Before Reaching for Fungicide

When roots remain wet and oxygen-poor, root rot can continue even after a fungicide application. Water molds such as Pythium and Phytophthora thrive in wet conditions, but salinity, ammonium toxicity and compaction can also damage roots and mimic disease.

Five actions to take now

Check the roots. Healthy young roots are usually firm and light colored. Soft, dark or sloughing roots need attention.
Measure moisture before irrigating. Do not water only by the clock. Compare pot weight, substrate moisture or sensor readings with plant demand.
Improve drainage and air space. Unblock drainage holes, avoid compacting media and do not let containers sit in standing water.
Remove heavily affected plants. Leaving dying plants in a production area can increase inoculum and allow waterborne pathogens to spread.
Sanitize between crops. Clean trays, pots, benches and tools. Keep hose ends off the floor and start with healthy transplants.

Use crop-protection products carefully

Not every root-rot product controls every pathogen. Products effective against oomycetes may not control Fusarium, Rhizoctonia or other causes. Obtain a diagnosis and follow the crop label. Rotate effective modes of action where resistance is a concern.

Bottom line: a treatment cannot compensate for a constantly saturated root zone. Restore drainage, oxygen and sanitation before expecting reliable disease control.

Sources: University of Connecticut IPM: Root Rot Diseases of Greenhouse Crops; Cornell Greenhouse Horticulture root-rot guidance.

Do you irrigate by a fixed schedule or by measured crop demand?

Featured photo: Katrien Van crombrugghe via Unsplash.