Common Root Rot of Cereals

Bipolaris sorokiniana

Description:

Browning sub crown internode and crown of plants from tillering to maturity. Roots are not discoloured. In severe cases, the crown, stem bases and tiller buds may have a brown rot. Individual or groups of plants may appear paler and stunted with fewer tillers producing smaller heads but these symptoms are rarely obvious. Symptoms are usually most obvious after flowering.
The spores are multicellular, black and oval shaped when viewed under a microscope.

Species Affected:

Barley, Cereal Rye and susceptible Wheat and Triticale varieties.
Grasses.

Biology:

Transmitted on stubble and seed.
Favoured by warm moist conditions.
Persistent in the soil.
Oats is highly resistant but not sufficient for a disease break.
Broad-leaved plants are rarely affected and used for a disease break.
Summer crops are more effective at reducing soil spore loads than winter crops.
Triticale resistance depends on the variety.

Life Cycle:

Spores survive in the soil, on crop residues and seed over summer and germinate in autumn to infect the newly planted crop. The disease spreads through the lower portions of the plant and produce spores in late spring to summer.

Origin and History:

Distribution:

Occurs in both summer and winter rainfall crops. Distribution affected by climate, soil type and agronomy.

Significance:

Affects Barley, Cereal Rye and susceptible Wheat and Triticale varieties. Yield reduced by a reduction in the number of heads and grains per head.
Significant yield reductions may occur when half of the plants have some browning of the sub-crown internode and some are completely discoloured.
Yield losses in are usually around 5-15% in moderate to severely affected crops.

Management and Control:

Sow clean seed.
Sow resistant Wheat varieties. Avoid Barley in infested areas.
Ensure adequate nutrition.
Avoid areas where cereal stubble is present and burn or bury stubble.
Adjust rotations so there is a longer period between cereal crops.
Control grasses in crops and pastures.
Shallow sowing, deep ripping and direct drilling are reported to reduce the impact of the disease but are often variable.
Treatments that encourage vigorous early root growth appear to be beneficial.

Related and Similar Species:

Very similar to Crown Rot and Take-all.
Crown Rot (Fusarium graminearum Group 1)
Take-all (Gaeumannomyces graminis) usually has browning of the roots as well as the sub-crown internode.

References:

1295

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.