Septoria Nodorum Blotch of Wheat
Leptosphaeria nodorum, Septoria nodorum
Description:Tan to brown (sometimes yellow) oval or irregularly shaped blotches with yellow rims initially on leaves in late winter to spring becoming grey as they increase in size and the leaf dies. Tiny grey/brown fruiting bodies can sometimes be seen in the centre of the blotches. In young crops many leaf tips may be yellow. It spreads to stems and glumes as the disease progresses and becomes very noticeable. The whole ear may have initially brown then grey blotches all over it by the end of the season leading to shrivelling of grain. Fruiting bodies are often seen on glumes and stem nodes.
Species Affected:Wheat, Barley, Barley Grass, Brome Grass, Cereal Rye.
Lupins, Oats, Peas and broad-leaved plants are resistant.
Biology:More common in warm, moist conditions.
Survives on infected plant debris.
Disease development favoured by warm wet weather.
Life Cycle:After rains in autumn large numbers of spores are produced and spread in the wind to infect young crops. Early sown are most likely to be heavily infected. These infected plants soon produce spores that are spread by raindrop splash within the crop as are residual spores any underlying stubble.
Origin and History:Distribution:
Causes loss or shrivelling of grain.
30% yield loss can occur in humid seasons.
Management and Control:Sow resistant varieties. See Disease Susceptibility of Wheat Varieties
Avoid sowing before May 15 in high rainfall areas and before May 7 in medium rainfall areas.
Avoid areas where Wheat stubble is present.
Burn, bury or graze Wheat stubble to reduce it as much as possible. This will reduce the severity of the disease in the current and future seasons.
Use longer rotations. Rotate with Barley, Lupins, Oats, Peas or pasture.
Avoid continuously cropping to Wheat especially if stubble is retained.
Spray with fungicides such as flutriafol(Impact®), propiconazole(Tilt®) or tebuconazole(Folicur®) at the flag leaf stage if more than 100 mm rain is expected in the next 8 weeks.
In high risk situations such as a susceptible variety on an infected wheat stubble full control with 400 mL/ha flutriafol in furrow followed by 250 mL/ha propiconazole250 at Zadok's 31 and 55 is usually profitable.
In lower risk situations a propiconazole250 at 250 mL/ha at 70 % flag leaf emergence is used if flag-2 leaf has more than 10% infection. Lower rates applied every 2-3 weeks are usually more effective than single larger doses.
Related and Similar Species:Septoria Nodorum Blotch of Wheat (Phaeosphaeria nodorum)
Yellow Spot of Wheat (Pyrenophora tritici-repentis)
Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.