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Fusarium oxysporum f. sp. vasinfectum Fusarium oxysporum f. sp. vasinfectum (G.F. Atk.) W.C. Snyder & H.N. Hansen · formerly or also: Fov
Fusarium wilt of cotton is caused by a soil fungus that invades the roots and blocks the water-conducting vessels. Seedlings may die, and older plants yellow, wilt, lose leaves and become stunted, with brown streaks inside the stem. In many regions the disease is worst together with root-knot nematodes, but newer strains such as race 4 in the United States and the Australian strain cause severe disease on their own. The fungus survives in soil for many years and can be carried on seed.
Fusarium wilt of cotton is caused by Fusarium oxysporum f. sp. vasinfectum Fusarium oxysporum f. sp. vasinfectum (G.F. Atk.) W.C. Snyder & H.N. Hansen, a fungus (ascomycete, soil-borne) (order Hypocreales, family Nectriaceae).
Older or alternative scientific names: Fov.
Found in cotton-growing regions worldwide, including Asia, Africa, the Americas and Australia. Race 4 was reported in California in the early 2000s and in Texas and New Mexico from 2017, and a distinct strain was found in Australia in 1993.
| Region | Status |
|---|---|
| Asia | Widespread; major in China, India and Central Asia |
| Africa and the Middle East | Present; historically important in Egypt and Sudan |
| Americas | Widespread; race 4 spreading in the south-western US |
| Oceania | Australian strain present since 1993 |
A soil fungus that forms long-lived thick-walled spores (chlamydospores) in dead tissue. Races and genetic groups differ in aggressiveness and in whether they need root-knot nematodes to cause disease. Identification of the race requires laboratory tests. Because many races cause disease only with root-knot nematodes, a nematode test is part of the diagnosis.
| Crop stage | What you see |
|---|---|
| Seedlings | Yellowing and wilting of seed leaves and death of seedlings, often in patches (especially with race 4). |
| Older plants | Leaf margins yellow, then brown; wilting, leaf drop and stunting, often worse on one side of the plant. |
| Inside the stem | Continuous dark brown streaks in the water-conducting tissue of the lower stem and roots. |
Chlamydospores in soil germinate near cotton roots and infect them, often through wounds made by root-knot nematodes. The fungus grows into the xylem and spreads upward. When infected plants die, new chlamydospores form in the tissue and return to the soil. The fungus is spread by infested soil on equipment, irrigation water, plant debris and seed.
| Stage | Duration | Notes |
|---|---|---|
| Chlamydospores in soil | Survive many years | Main inoculum. |
| Root infection | From seedling stage | Aided by root-knot nematodes for many races. |
| Vascular colonisation | Weeks | Wilting and stem browning. |
| New spores in dead tissue | End of season | Builds up soil inoculum. |
Disease is favoured by warm soils (about 25-30 °C); cool early-season conditions can favour seedling infection by race 4.
One main cycle per crop; inoculum builds up with continuous cotton.
Sandy soils with root-knot nematodes, continuous cotton, susceptible varieties (especially Pima cotton for race 4), potassium deficiency, and movement of infested soil, water and seed.
There is no economic threshold; management is preventive, based on variety choice, clean seed and sanitation, and nematode management where nematodes are involved.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Plant deaths and wilting cause patchy to severe yield losses; race 4 can kill large numbers of seedlings in susceptible varieties, and infested fields may become unsuitable for those varieties.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
No fungicide treatment controls the wilt in the field; seed treatments protect seedlings only partly, and nematicides are used where root-knot nematodes increase disease. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
Cotton (upland and Pima/Egyptian cotton) is the main host; some strains also infect a few other plants in tests.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.