<P> White rust pathogens create chlorotic (yellowed) lesions and sometimes galls on the upper leaf surface and there are corresponding white blister - like dispersal pustules of sporangia on the underside of the leaf . Species of the Albuginaceae deform the branches and flower parts of many host species . Host species include most if not all plants in the Brassicaceae family, common agricultural weeds, and those specified below . </P> <P> White rust is an obligate parasite . This means it needs a living host to grow and reproduce . The Albuginaceae reproduce by producing both sexual spores (called oospores) and asexual spores (called sporangia) in a many - stage (polycyclic) disease cycle . </P> <P> The thick - walled oospores are the main overwintering structures, but the mycelium can also survive in conditions where all the plant material is not destroyed during the winter . In the spring the oospores germinate and produce sporangia (s . sporangium) on short stalks called sporangiophores that become so tightly packed within the leaf that they rupture the epidermis and are consequently spread by the wind . The liberated sporangia in turn can either germinate directly with a germ tube or begin to produce biflagellate motile zoospores . These zoospores then swim in a film of water to a suitable site and each one produces a germ tube - like that of the sporangium - that penetrates the stoma . When the oomycete has successfully invaded the host plant, it grows and continues to reproduce . </P> <P> Favorable conditions for the dispersal and consequent infection of white rust from diseased to healthy plants are most common in the autumn and spring seasons . This pathogen prefers cool, moist conditions for the spread and formation of new infections . Conversely, it rarely infects in warm, dry conditions . Albugo is very temperature sensitive, with the optimal temperature range for infection between 55 and 77 ° F (13 and 25 ° C). The likelihood of germination and infection is considerably lower if temperatures deviate too far outside this optimum range . </P>

Albugo reproduces asexually by means of structure which are called