Daucus maximus, Ridolfia segetum and Caucalis tenella, members of the Umbelliferae, were found to be foliage hosts of naturally occurring Alternaria dauci in Israel. A. dauci was also isolated from Daucus maximus seed.
When infected cultivated carrot petioles were stored dry for 3 months, A. dauci retained its ability to spore, which was lost, however, in alternating wet and dry conditions, an effect paralleled by the loss of mycelial viability in similar soil storage tests. A. dauci colonizing moribund foliage stayed viable longer when the foliage was on the surface than when buried in soil at depths of 10 and 20 cm.
Viable thick-walled hyphae of A. dauci were found in the inner pericarp layer of Japanese seeds from which infected seedlings developed.