Mycologia, ASCOMYCOTINA, DOTHIDEALES, PLEOSPORACEAE .
Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images
A wide polymorphism characterises the symptoms on leaves caused by D. teres . But all the forms have some common aspects : dark brown necrotic lesions of different shapes and sizes surrounded by a chlorotic ring, generally forming a net.
This disease causes heavy loss in areas where intensive cultural practises are present.
1000 grains-loss in weight is reported.
The fungus is preserved on straw for about two years as chlamydospores and perithecia.
Conidia released from chlamydospores in autumn cause the primary attacks on leaves.
The fungus also persists in the seeds as mycelium.
Seed-borne infection is commonly transmitted from one geographical area to another.
The mycelium in the seeds directly contaminates the coleoptile.
The volunteers plants and grasses like Hordeum are sources of inoculum as well.
In winter the parasite slows down its functions.
The epidemics breaks between the swelling stage and the heading.
Perithecia form on the straw and stubble after the harvest.
Ascospores are active in the survival and dissemination of the fungus.
Conidia occur at 20 °C. in high RH conditions.
They are dispersed by the wind at a short distance.
Conidial germination requires a very high RH over a wide range of temperatures (3 - 31 °C.) with an optimum between 18 - 24 °C.
During the epidemics stage incubation lasts 4 days at 20 °C.
Contamination through ascospores occurs between 4 - 30 °C. with an optimum at 18 °C.
Use treated seeds.
Avoid direct sowing on stubble without ploughing.
Start fungicidal treatment according to local advice when symptoms occur on one of the last three barley leaves.
In severe attacks apply first treatment at the "one node" stage to delay the outbreak of the epidemics.
HYP3 on line : Species (scientific name), Diseases (common names), Glossary, Crops.