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

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46 Control of physiological leaf spot Keeping crops free from stress is the key to minimising the impact of physiological leaf spots. Some things can be done to minimise stress including variety choice, nutrition and also choice of fungicides Stresses from extreme weather events including frost, waterlogging, drought or prolonged sunshine are more challenging to manage. Variety Since some varieties are more susceptible to producing physiological leaf spots than others, varietal choice is one method to minimise their impact. In recent years, plant breeders have made advances in breeding varieties which are less susceptible to producing leaf spots. Nutrition PHYSIOLOGICAL LEAF SPOTS Crops should be adequately provided with nutrition from macro nutrients including nitrogen, potassium and phosphorus and micronutrients in particular manganese which can cause stress when plants are deficient. Nitrogen is most likely to be limiting in varieties grown for malting markets which require grain with a low nitrogen level (1.4%). Growers should therefore be aware that crops grown for these markets are at a greater risk from physiological leaf spots. Manganese deficiency is a common nutritional disorder in barley grown on soils with a pH greater than 6.0. Deficiency symptoms include the development of brown linear flecks on leaves which can be indistinguishable from some physiological leaf spots. Since manganese is an important component of many plant enzymes, deficient plants are likely to be more susceptible to the development of physiological leaf spots as the plants ability to produce superoxide dismutase enzymes will be reduced. Protection against manganese deficiency is through the use of seed and foliar manganese treatments. Soil applications are unlikely to be effective since soil levels are likely to be high, but the availability of soil manganese is limited at high soil pH.
Manganese deficiency symptoms on barley PHYSIOLOGICAL LEAF SPOTS 47 Magnesium deficiency is more likely to occur in acid soils since soil magnesium is less available to the crop at low soil pH. Leaves of plants affected by magnesium deficiency are likely to show necrotic leaf spots on the leaf margins. The underlying soil pH can be corrected using magnesian limestone. Where a foliar treatment is required, magnesium sulphate can be applied.
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 32 and 33: 30 Ramularia Ramularia concentratio
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 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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