Stem Rust:
essential data |
Disease Name, Other
Names, Crops Affected Causative
Agent, Synonyms,
Description
of the Agent Symptoms Prevention
and Treatment
Other Comments |
| Disease name |
Striped Rust |
| Other Names |
Black rust |
Causative Agent
|
Puccinia striiformis |
| Synonyms |
Puccinia glumarum |
| Crops Affected |
Wheat is the most important. Barley and some other grasses
and cereals are also affected. |
| Description of the Agent |
P. striiformis is a rust fungus, a member of the Uredinales
and ultimately members of the basidiomycetes (the club fungi, including
the mushrooms). They are called rust fungi because disease plants
show rust-colored orange patches on the infected plant parts. In addition
to structural features that are typical of basidiomycetes, they have
a complex life cycle with up to five forms of spore being formed.
It is one of these forms, the uredospore, that is rust colored.
|
| Symptoms |
The disease is first seen as small yellow pustules resembling stitching
on the leaves running parallel to the long axis of the leaf that coalesce
to form stripes. These break open some days later to reveal a mass
of rust-colored spores. The stripes can turn black as the disease
progresses and a new type of spore, the teliospore, develops. The
infection stresses the plant causing it to dry out as it matures.
Crop losses can reach 40%. |
| Prevention and Treatment |
Cultural practices, such as crop rotation are of no
great help as the mycelium can overwinter in moderate climates. Planting
of resistant varities of wheat is the best practice.
Effective fungicides include:
- Baytan 30F;
- Propaconizole
- Tridemefon.
These are applied once or twice early in the season, at about the
time the flag leaf emerges, and must not be applied within 8 weeks
of harvest. |
| Other Comments |
The disease is dependent upon relatively cool temperatures
(daytime highs of <15°C or 59°F) with spore viability dropping
off rapidly above that. Intermittent rain and heavy dews increase
tye efficiency of spore germination and there are simple models that
can predict the risk of an outbreak from climate data The mycelium
can survive a mild winter (lows of ›;-5°C, 23°F).
Strains of the fungus are specific for certain strains of wheat
and careless use of wheat strains resistant to a specific form of
the fungus can lead to the rapid development of new forms of the
fungus attacking the resistant wheat and this can give rise to epidemic
outbreaks. The resistance is not always present in young plants
and it may be necessary to use fungicides on them. |