Fusarium wilts and blights:essential data |
Disease Name,
Other Names, Crops
Affected Causative Agent, Synonyms,
Description of the Agent Symptoms,
Prevention and Treatment
Other
Comments |
| Disease name |
Fusarium
wilt |
| Other Names |
Fusarium vascular wilt |
Causative Agent
|
Fusarium oxysporum |
| Synonyms |
Variants of F. oxysporum
that are specific for different plant hosts are known and differentiated
as f. (formae) or f.sp. (forma speciae); e.g. F. oxysporum
f. sp. lycopersici attacks the tomato (Lycopersidon esculentum) |
| Crops Affected |
A wide range of vegetables,
plantation crops, ornamentals and turf grasses are attacked. |
| Description of the Agent |
Fusarium oxysporum
is an imperfect fungus (one with no known sexual stage) belonging to the
ascomycetes or sac fungi. It spreads by means of asexual spores (microconidia,
macroconidia, or chlamydospores.) Chlamydospores can survive in the soil
and mycelium can survive and overwinter in the waste from infected plants.
The fungus is extremely widespread (also described as a cosmopolitan distribution)
and once it becomes established in an area, it is essentially impossible
to eliminate it. |
| Symptoms |
The first sign of Fusartium
vascular wilt is often a yellowing or clearing of the outer edges of younger
leaves followed by drooping. The infection is already well established
as the fungus usually invades the plant through the roots where it travels
through the xylem of the plant that moves water and nutrients from the
root to the crown of the plant. As the mycelium ramifies through the plant,
the xylem becomes obstructed and the plant wilts and dies. Older plants
may survive but are often stunted in growth. Typically, infected plants
show a ring of dead brown vascular tissue near the bottom of the stem.. |
| Prevention and Treatment |
It is very difficult
to remove F. oxysporum when it becomes established as it can grow
saprophytically (on dead organic matter such as crop waste) in the absence
of a susceptible crop. The only effective response is soil sterilization,
which is far too expensive for most farmers. Some control can be achieved
with fungicides but the use of resistant cultivars of plants is the preferred
approach., |
| Other Comments |
Fusarium wilt of tomato
is probably the most economically significant disease caused by F.
oxysporum, but it shows a large number of formae speciale that
are specific pathogens of other plants including:
- Asparagus;
- Banana;
- Carnation;
- Cotton
- Cucurbits (squash, melons, cucumbers);
- Ginger;
- Snowpeas;
- Soybean.
F. oxysporum has been considered a biological herbicide by the
US and Russia. The US has supported research into the development of
a coca-specific variant to use against cocaine plantations in Colombia
and the fUSSR attempted to develop one that would attack the opium poppy,
apparently to prevent Afghan mujahideen using opium sales to pay for
weapons to oppose the Soviet invasion of the country.
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