Root Rot Control — How to Identify, Treat & Prevent Root Rot in Soybean, Chickpea & Tomato
Root rot is caused by soil-borne fungi and oomycetes that attack the root system in waterlogged or poorly-drained soils, causing wilting, yellowing, and plant death. Seed treatment, drainage improvement, and Trichoderma biocontrol at sowing are the most effective prevention strategies.
How to identify root rot
Watch for these signs in your field.
Wilting despite adequate soil moisture
Plants show daytime wilting even when soil moisture is sufficient — the classic sign that root function is compromised and the plant cannot take up water through rotted root tissue.
Yellowing lower leaves
Lower leaves turn yellow progressively from the bottom of the plant upward as the root system loses its ability to supply nutrients, while upper leaves may remain green until late stages.
Brown-black discolouration of roots
Pulling the plant reveals brown to black, soft, water-soaked roots that smell rotten. Healthy roots should be white and firm. Severely affected plants pull out of the soil easily with almost no root resistance.
How to control root rot
Follow this step-by-step protocol for best results.
Improve drainage and reduce waterlogging
Root rot pathogens (Pythium, Fusarium, Phytophthora) thrive in waterlogged soils with poor aeration. Make raised beds or improve field drainage before sowing. Avoid over-irrigation, especially in heavy clay soils. Allow the top 2–3 cm of soil to dry between irrigations.
Apply a soil drench fungicide at early symptom
Apply Carbendazim 50% WP (1 g/L) as a soil drench around the root zone at first signs of wilting. For Pythium-based root rot, use Metalaxyl seed treatment before sowing. Trichoderma viride soil application (5 g/L water) at sowing provides biological suppression of root pathogens.
Use seed treatment and crop rotation
Treat seeds with Thiram 75% WP (3 g/kg) or Metalaxyl 35% WS (6 g/kg) before sowing in fields with a history of root rot. Rotate crops with non-host species (cereals after legumes) for a minimum of 2 seasons. Incorporate organic matter to improve soil biological activity and natural suppression.
Which crops are at risk?
Tap a crop for the full pest management guide.
Root Rot — Common Questions
What is the difference between Pythium and Fusarium root rot?
Pythium root rot causes soft, water-soaked, dark brown rot of roots and often affects seedlings in waterlogged conditions — it is an oomycete (water mould), not a true fungus, so it responds to Metalaxyl but not Carbendazim. Fusarium root rot causes dry, reddish-brown internal discolouration of roots and crown and is more common in older plants under stress. Carbendazim is effective against Fusarium. A lab diagnosis or send a sample to your state agriculture university for confirmation.
How do I apply a soil drench correctly for root rot?
Mix the fungicide (e.g., Carbendazim 50% WP at 1 g/L) in water and apply 200–500 ml per plant directly around the base of the stem into the root zone. Apply in the late afternoon when soil temperature is lower. Avoid applying to already waterlogged soil. Repeat after 10–15 days if wilting persists.
How can I prevent root rot at the time of sowing?
Use Trichoderma viride (5 g/kg seed) plus Thiram 75% WP (3 g/kg) as a combined seed treatment. Apply Trichoderma viride (2.5 kg/ha mixed with 50 kg FYM) to the soil at sowing. Make raised beds in heavy soils. Avoid sowing into fields with a known root rot history without at least a 2-year rotation with a non-susceptible crop.
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