This brief review reports the results of phytopathological investigations carried out on onion seed crops in the northern Umbrian Tiber Valley (central Italy). Downy mildew infections (Peronospora destructor) and also Botrytis cinerea attacks are the major fungal diseases for the crops. All varieties, even though with different intensity and incidence, are susceptible to both pathogens. Finally, employed control strategies are critically discussed, pointing out on agronomic methods which may also contribute in reducing favourable conditions for both diseases.