Fusarium wilt is a vascular disease caused by Fusarium oxysporum, a soil-borne fungus that enters through roots and grows into the xylem, the water-conducting tissue. As it blocks the vessels, the plant cannot move water. Other Fusarium species, such as F. solani, cause crown and root rot, and several species also infect buds.
In practice
Symptoms often start on one side of a plant or one branch: leaves yellow and wilt, then the whole plant collapses even in moist media. Cutting the lower stem lengthwise shows brown or reddish streaks in the wood. The fungus survives in soil for years as resting spores and spreads on media, tools, water and clones. There is no cure for an infected plant; remove it with its medium, sanitise containers and tools, and do not reuse that soil. In hydroponics it often appears alongside Pythium. Clean propagation material and fresh media are the prevention.
Don't confuse with
- Pythium: a water mould causing slimy root rot rather than vascular streaks.
- Underwatering: plants recover after watering; fusarium wilt does not.
- Septoria leaf spot: spots on leaves, no wilt.
The plant's water-conducting tissue, which carries water and dissolved mineral ions upward from roots to leaves, driven mainly by transpiration.Decay of roots by pathogens such as Pythium, Fusarium, Rhizoctonia or Phytophthora, usually triggered by low oxygen, heat and waterlogging around the roots.A genus of oomycete water moulds, such as Pythium myriotylum and P. aphanidermatum, that cause brown, slimy root rot, especially in warm hydroponic systems.Pest and disease prevention by changing how the crop is grown, such as humidity, airflow, spacing, watering and cultivar choice, so pests and pathogens struggle to establish.Underwatering is letting the medium dry too far between waterings, so the plant loses turgor and wilts, with limp, papery leaves and crisping edges if repeated.A fungal leaf disease caused by Septoria cannabis that produces tan to grey spots with dark margins and yellow halos, starting on lower leaves.The collapse of seedlings or cuttings when soil-borne pathogens such as Pythium, Rhizoctonia solani and Fusarium rot the stem at the soil line.Cleaning and disinfecting rooms, tools, containers, irrigation and people's clothing so that pests and pathogens are not carried from plant to plant or crop to crop.Holding incoming plants, clones or seeds apart from the main grow, under observation and sometimes treatment, until they are shown to be free of pests and disease.
