The ability of Peridermium pini and Cronartium flaccidum
aeciospores and mycelium to infect known (Vincetoxicum spp., Pedicularis
spp.,
Paeonia spp.) and potential (Melampyrum spp., Pyrola
sp., Dactylorhiza sp., Solidago sp., Salix sp.,
Geranium sp. and Maianthemum sp.)
alternate hosts was tested. None of the mycelial cultures and only 10%
of the aeciospore samples produced uredinia or telia on the
tested species suggesting that most aeciospores in Finland belong to the
autoecious P. pini. Aeciospores from three locations in
northern Finland, however, produced uredinia or telia on Vincetoxicum
mongolicum, V. nigrum, V. fuscatum, Paeonia
anomala, three
P. officinalis cultivars, Melampyrum sylvaticum and Pedicularis
palustris either in vitro or in vivo, indicating
that these aeciospores belong
to the heteroecious C. flaccidum, which occurs sporadically in
Finland. Interestingly, the host-specificity of C. flaccidum encountered
in Finland was very low (e.g. one sample produced uredinia or telia on
eight species). This, added to the wide distribution
of Melampyrum spp. over northern Fennoscandia, suggests that the
main alternate hosts for C. flaccidum in Finland may
be in Melampyrum rather than Pedicularis.