Light brown colouring of the base of tillers and a pink discolouration around the crown and under the leaf sheaths. Odd tillers or whole plants may become bleached over winter and develop white heads with no grain at maturity or may have normal grain.
Seedlings occasionally show yellowing and death.
A pink discolouration caused by the salmon coloured spores may develop under the leaf sheath. General decay of the base of the plant and other symptoms may be seen at any stage but is usually more obvious after flowering.
Part or all of the head is white or yellow and often without grain or with shrivelled and pinkish grain. In humid conditions the white heads may turn grey of black.
Paddock symptoms include scattered white heads to large patches of white heads that are often more prevalent on wheel tracks that are most noticeable as the crop ripens or at harvest. It is often associated with depressions or wetter areas of the paddock. Nodes of infected plants are often pinkish. The straw may be full of a white to pink fungus when split.
The spores are multi celled and banana shaped when viewed under a microscope.
Species Affected:
Cereals, grasses.
Durum Wheat is more sensitive than other cereals
Barley Grass and Phalaris are very susceptible.
Oats are partially tolerant.
Most broad-leaved species are resistant.
Biology:
Requires warm moist conditions.
Tends to build up after a series of dry springs.
Survives on cereal and grass residues for 2 years.
Life Cycle:
Spores from infested stubble germinate in autumn and infect Wheat seedlings. The fungus proliferates in stems over winter reducing the supply of water and nutrients to the head. Spores are produced in spring and over summer in the stubble. Spores may remain viable in stubble for about 18 months.
Origin and History:
Distribution:
Occurs on most soil types but is often more severe on poorly drained areas and on heavy black or grey soils.
More common in the northern wheatbelts of WA and NSW.
Significance:
May cause significant yield losses in Wheat, Barley, Triticale and most grasses especially in stubble retention systems.
The disease is usually worst in seasons with a wet start and dry finish.
Management and Control:
Burn or bury infected cereal stubble.
Adjust crop rotation to reduce cereals and grasses.
Control grasses in pastures, broad-leaved break crops and fallows.
Plant resistant varieties. Oats are somewhat tolerant and provide a partial disease break.
Don't sow cereals after cereal crops or grassy pastures.
12-18 months fallow usually provides reasonable control.
Barley Grass and Phalaris are severely affected and should be controlled in break crops.
Reduce stubble or encourage breakdown by grazing, burning, trampling, burying baling or raking.
Cultivation at seeding provides partial control by enhancing stubble breakdown.
Planting tolerant cereal cultivars reduces yield losses but rarely reduces the carry over of disease into the following season.
Apply adequate fertiliser and especially Zinc.
Control weeds, adjust agronomy and balance Nitrogen fertiliser to reduce the risk of water stress in spring.
Most broadleaved plants are resistant and are useful for reducing the disease.
Brassica break crops are more effective than legume break crops. A break crop of Canola or Mustard led to a 50% reduction in severity of disease in a following susceptible Wheat whereas Chickpeas resulted in a 30% reduction (Simpfendorfer, 2004)
Avoid Durum wheats in high risk situations.
Planting cereals between the rows from last season usually decreases the disease by 50% and results in a 5% yield increase and is a useful technique for low disease situations. In high disease situations the loss in yield due to the disease is not compensated for by the benefits of inter row planting (Simpfendorfer, 2007)
Biological Control:
A naturally occurring fungus (Trichoderma spp.) appears to limit Crown Rot effects and is encouraged by Brassica (Canola) crops.
Related and Similar Species:
Copper deficiency has similar symptoms.
Take-all (Gaeumannomyces graminis)
Head Scab of Wheat (Fusarium graminearum Group II)
Yellows of Brassicas (Fusarium oxysporum f.sp. conglutinans)
References:
1208
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 for more information.