Yellow Spot of Wheat

Yellow Leaf Spot of Wheat

Pyrenophora tritici-repentis

Description:

Tan, irregularly shaped or elongated blotches usually with yellow margins on both sides of leaves in late winter to spring. The leaf tips often wither where the lesions join. Heavy infection may cause total withering of leaves. In southern areas it is most often seen on young crops while in northern areas and WA it is often seen at all stages of the crop.
Associated stubble usually has small black fruiting bodies with short, hair like projections.

Species Affected:

Wheat including Durum Wheat, Triticale and some grasses.
Barley and Cereal Rye are partially susceptible.
Lupins, Oats, Peas and broad-leaved species are resistant.

Biology:

Survives over summer on stubble.
Leaves must remain wet or six hours for infection to occur. Infection occurs over a wide range of temperatures.
2 types of spores produced. Those from the over summering fruiting bodies spread short distances and those from infected green leaves are wind dispersed.
Barley, Cereal Rye and Oats may be infected if rain occurs near harvest and then these stubbles may infect a following Wheat crop.

Life Cycle:

Over summering fruiting bodies produce spores after rain that spread short distances to infect Wheat seedlings under wet conditions. Infected leaves produce wind-dispersed spores that rapidly spread the disease within the crop and to other crops.

Origin and History:

Distribution:

Significance:

Management and Control:

Sow resistant varieties. See Disease Susceptibility of Wheat Varieties.
Avoid planting 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.
Use longer rotations. Rotate with Lupins, Oats, Peas or pasture. Barley can carry some disease.
Spray with fungicides such as propiconazole(Tilt®) or tebuconazole(Impact®) at the flag leaf stage if more than 100 mm rain expected within the next 8 weeks.
Seed dressings and in furrow treatments are generally not effective on stubble borne net blotches.
Generally chemical control is not profitable unless susceptible varieties are grown and/or crops are on infected stubbles.

Related and Similar Species:

Barley Stripe of Barley (Pyrenophora graminea)
Net Blotch - Net Form of Barley (Pyrenophora teres f. teres)
Net Blotch - Spot Form of Barley (Pyrenophora teres f. maculata)
Halo Spot of Barley (Pseudoseptoria stomaticola)
Septoria Nodorum Blotch (Phaeosphaeria nodorum)
Septoria Tritici Blotch (Mycosphaerella graminicola)

References:

Acknowledgments:

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