Horticultural crops : Grapes 
       
        
          
            
                
                  
                    
                      
                            Downy mildew: Plasmopara viticola
                            
                              
                                
                                  Symptoms 
                                    
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Irregular, yellowish, translucent sports on the upper surface of the leaves. 
                                       
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Correspondingly on the lower surface, white, powdery growth on leaves. 
                                       
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Affected leaves become, yellow, brown and gets dried. 
                                       
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Premature defoliation. 
                                       
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Dwarfing of tender shoots. 
                                       
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Brown, sunken lesions on the stem. 
                                       
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White growth of fungus on berries which subsequently becomes leathery and 
                                       
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shrivels. 
                                       
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Later infection of berries result in soft rot symptoms. 
                                       
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No cracking of the skin of the berries. 
                                       
                                     
                                    
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Spread : Through sporangia by wind, rain etc. 
                                       
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Survival : As oospores present in the infected leaves, shoots and berries. Also as 
                                       
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dormant mycelium in infected twigs. 
                                       
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Optimum temperature : 20-22°C 
                                       
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Relative humidity : 80-100 per cent 
                                       
                                     
                                    Management 
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                                  | Grapes downy mildew in bunches | 
                                 
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