Septoria Tritici Blotch of Wheat

Mycosphaerella graminicola

Septoria tritici

Description:

Tan to brown (occasionally silver) irregularly shaped blotches with thin yellow rims on the leaves in late winter to spring. The blotches may run along the veins sometimes and have straight sides. There are usually black specks or fruiting bodies within the blotch especially later in the season.
Lesions with black specks are characteristic of this disease.

Species Affected:

Wheat, Cereal Rye.
Barley, Lupins, Oats, Peas and broad-leaved plants are resistant.

Biology:

More common on early sown crops.
Survives from one season to the next on wheat residues or stubble.

Life Cycle:

The fungus survives summer on wheat stubble and after the first autumn rains produces large quantities of spores that are spread large distance by wind. These spores infect emerging crops and early sown crops are at greatest risk. 3-4 weeks infections fruiting bodies appear on leaves and again produce large numbers of spores that are spread from leaf to leaf within the crop by rain drop splash. Frequent, heavy rainfall at this time increases the spread and severity of the disease. Dry periods of 3-4 weeks in winter and spring can arrest the spread of disease.

Origin and History:

Distribution:

More common in high rainfall areas.

Significance:

30% yield loss in wheat can occur in seasons favourable to the disease.

Management and Control:

Sow resistant varieties. See Disease Susceptibility of Wheat Varieties. This reduces the effect on the current crop and reduces inoculum levels for future crops.
Avoid areas where Wheat stubble is present.
Burn, bury or graze stubble to reduce the amount of wheat debris that will produce spores in autumnů.
Avoid sowing susceptible varieties early (before May15) in high rainfall areas and before May 7 in medium rainfall areas.
Avoid continuous Wheat cropping especially if stubble is retained.
Use longer rotations. Rotate with Barley, Lupins, Oats, Peas or pasture.
Some seed treatment fungicides will reduce early season disease but often don't reduce final yield losses.

Related and Similar Species:

Septoria Nodorum Blotch of Wheat (Phaeosphaeria nodorum)
Ring Spot of Brassicas (Mycosphaerella brassicola)
Yellow Spot of Wheat (Pyrenophora tritici-repentis)

References:

1293

Acknowledgments:

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