CONTEXTS 



PAGE 



Nomenclature of the causal organism 3 



Distribution 5 



History 6 



Suscepts 7 



Varietal susceptibility 8 



Importance and nature of the losses 9 



Field observations on the occurrence of onion mildew 11 



Signs and symptoms 11 



Time of occurrence 12 



Location of diseased plants 13 



Temperature and moisture relations 13 



Sources of primary inoculum 14 



Systemically infected plants 15 



Infested soil 15 



Infested seed 16 



Infected seed 16 



Environmental factors 22 



Field observations 22 



Experimental work 23 



Relation of temperature to the formation of conidiophores and conidia 23 



Relation of humidity to the formation of conidiophores and conidia 23 



Spore germination '. 26 



Technic 26 



Effect of temperature on the time and the percentage of germination of the conidia. . 27 



Infection 32 



Incubation period 32 



Effect of temperature on infection 33 



Control 34 



Summary 35 



References 36 



