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Loose Smut
Ustilago nuda
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General Description
Loose smut is a seed borne disease which affects winter and spring barley.
A crop will appear normal up to head emergence. Once the heads have emerged, the heads will be covered in black spores. Affected plants tend to be shorter at this stage, and when the spores have dispersed, it will be apparent that no grains will be produced from the head.
Biology
Loose smut is caused by the fungus Ustilago nuda. It is a seed borne fungus which is deep seated within the grain. This is the reason why systemic seed treatments are required to control it.
Crops can become infected at flowering from spores which are wind dispersed from plants showing the typical loose smut symptoms. Grains will develop normally, butthe fungus will grow inside the grain.
After sowing, plants will germinate and develop normally. The fungus will however be grwoing withinthe plant. Symptoms will only become obvious at heading time, when the grain sites will be taken over by the black spores.
Advice
For effective control, test the seed and reject seed with high levels of contamination.
Systemic seed treatments can effectively control seed stocks with moderate levels of contamination.
The maximum permitted infection in certified seed is 0.5%. It is therefore advisable not to sow farm-saved seed where levels exceed 0.5% without an effective seed treatment.
Diary
July
Time to think about seed treatments
Seed treatments play an important role in ensuring a good start for a crop. More...
August
Check seed for germination and seedborne diseases
Test seed for seedborne diseases and germination. More...