Persistence of Aschersonia aleyrodis, a fungal pathogen of whitefly, was studied on cucumber, gerbera and poinsettia. Germination
capacity and infectivity of conidia, which stayed on the plants for up to 1 month, were assessed. Average germination of conidia on
the leaves was low (< 14%), whereas most of the conidia transferred from the leaf to water agar were viable, even after having
been on the leaf surface for 1 month. Germination capacity was highest on cucumber, followed by poinsettia and lowest on gerbera.
On cucumber leaves, conidia stayed viable and were able to infect 90% of whitefly nymphs 31 d after spore application. On gerbera,
germination capacity decreased considerably from 80% (day 0) to 40% (day 31). This was reflected in nymphal mortality, which
declined from 75% to 40%. Despite the high germination capacity (60%) of conidia on poinsettia after an exposure of one month,
nymphal mortality decreased from 70% at the day of spore application to 10% after 3 d at leaf surface, and remained low
throughout the monitoring period. Relations between germination capacity, infectivity and the host plant environment such as
phyllosphere microorganisms, secondary plant metabolites and microclimate are discussed.