a guide to the recognition and understanding of ramularia and other ...

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30 Ramularia Ramularia concentration concentration from from spore spore trap trap (pgrams) (pgrams) 30000 30000 25000 25000 20000 20000 15000 15000 10000 10000 LIFECYCLE 5000 Seed infection 5000key source of infection 0 0 1st May 1st May 05 epidemics Ramularia leaf spot and epidemics spore and spore movement Ramularia epidemics and spore movement Seed main Early spore dispersal Late spore source of linked to leaf wetness dispersal a source 25 infection Winter leads – Spring to secondary Spore dispersal of seed– infection barley barley infection minor impact on disease disease epidemic but source of seed infection? 20 15th May 15th May 05 Ramularia spores Date Date Winter Winter barley barley Spring barley Spring barley 29th May 29th May 05 12th June 12th 05 June Ramularia leaf spot epidemics and spore movement Ramularia lifecycle GS0 Ramularia seed-borne Seed treatments? GS75-83 Ramularia symptoms on heads and awns Asteromella spores on straw Ramularia leaf spot 26th June 26th05 June 10th July 10th 05July 24th July 05 24th July 7th Aug 05 7th Aug Ramularia lifecycle G10-13 Ramularia detectable by diagnostics but no visual symptoms Airborne spores disperse when leaves are wet GS65 Physiological and weather stresses lead to rubellin production by fungus. Symptoms appear when rubellin is activated by light 21st Aug 05 21st Aug 15 10 5 0 GS25-30 Ramularia spots on dying leaves % Leaf area infected GS25-30 Fungicides can reduce later disease epidemic. GS45-49 Is best timing to protect crops with fungicide Fungus detected inside leaves 2-4 weeks before symptoms appear. 25 20 15 10 5 0 % Leaf area infected
CONTROL MEASURES 31 Control measures for ramularia leaf spot Varietal resistance Varieties differ in their susceptibility to ramularia leaf spot symptoms. In the UK spring barley varieties which show low levels of ramularia leaf spot include Decanter, Belgravia and NFC-Tipple High levels of Ramularia collo-cygni fungus can be found in the seed and developing leaves of the variety Decanter. The mechanism for resistance may therefore be a matter of the host plant being able to tolerate or break down the rubellin toxins produced by the fungus. Spring barley varieties which are most susceptible include Cocktail, Optic and Forensic. Yield losses associated with the disease can be as high as 1.0 tonne per hectare. In resistant varieties, yield losses are 0.1-0.2 tonnes per hectare. Average yield losses in Scotland for spring barley are 0.4 tonnes per hectare which equates to a loss of £10 million per year. Winter barley varieties also show different levels of resistance or tolerance to ramularia leaf spot. The malting barley variety Pearl exhibits low levels of symptoms whilst Flagon and Cassata are more susceptible. The feed barley variety Retriever can also be classified as susceptible. Seed health and seed treatments It is advisable to sow seed with low levels of contamination of Ramularia collo-cygni, particularly in regions where the disease is not a major threat, since seed transmission is a real risk for spreading this disease. However finding seed which is completely free from the pathogen is rare, even in the east of England where the disease is not perceived to be a major disease threat. Choosing seed stocks with less than 1pg of DNA per 100ng of total DNA in regions where the disease has yet to become established is recommended in the absence of effective seed treatments. Although seed is an important source of infection, currently available seed treatments have little impact on the fungus.
Page 1: A GUIDE TO THE RECOGNITION AND UNDE
Page 4 and 5: 2 Contents RAMULARIA Distribution C
Page 6 and 7: 4 RAMULARIA LEAF SPOT DISTRIBUTION
Page 8 and 9: 6 RAMULARIA LEAF SPOT DISTRIBUTION
Page 10 and 11: 8 Early stages SYMPTOMS What are th
Page 12 and 13: 10 SYMPTOMS Pepper spot symptom of
Page 14 and 15: 12 Later stage SYMPTOMS The rectang
Page 16 and 17: 14 SYMPTOMS Extensive ramularia lea
Page 18 and 19: 16 SYMPTOMS Ramularia leaf spot sym
Page 20 and 21: 18 SYMPTOMS Ramularia leaf spot sym
Page 22 and 23: 20 SYMPTOM APPEARANCE When do sympt
Page 24 and 25: 22 LIFECYCLE Disease lifecycle The
Page 26 and 27: 24 LIFECYCLE Spore dispersal Leaf w
Page 28 and 29: 26 LIFECYCLE Infection of barley by
Page 30 and 31: 28 LIFECYCLE Ramularia collo cygni
Page 34 and 35: 32 CONTROL MEASURES Foliar fungicid
Page 36 and 37: 34 Fungicide choice CONTROL MEASURE
Page 38 and 39: 36 Physiological leaf spots Physiol
Page 40 and 41: 38 PHYSIOLOGICAL LEAF SPOTS Advance
Page 42 and 43: 40 PHYSIOLOGICAL LEAF SPOTS Physiol
Page 48 and 49: 46 Control of physiological leaf sp
Page 50 and 51: 48 PHYSIOLOGICAL LEAF SPOTS Magnesi
Page 52 and 53: 50 FUNGAL DISEASES CAUSING SYMPTOMS
Page 54 and 55: 52 FUNGAL DISEASES CAUSING SYMPTOMS
Page 56 and 57: 54 Septoria nodorum FUNGAL DISEASES
Page 58 and 59: 56 REFERENCES AND FURTHER READING R
Page 60 and 61: 58 ACKNOWLEDGEMENTS Acknowledgement
Page 62: The Chemical Company

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