Competing fungi in white button mushroom (Agaricus bisporus, champignon) cultivation
causes significant episodic losses. One of these competing fungi is known as smoky
mould. It owes its name to the production of high numbers of spores after the disturbance
of compost, which resembles smoke. We investigated strains isolated from smoky mould
cases in the Netherlands, UK and Canada and show that these outbreaks were caused
by a new Penicillium species, named P. hermansii sp. nov. (type strain CBS 124296(T)).
Several Penicillium species are reported to cause smoky mould. However, we so far
have no indications that smoky mould is caused by other Penicillium species than P.
hermansii. This species belongs to section Exilicaulis and differs from other Penicillia
by its slow growth rate on Czapek yeast agar (CYA) and malt extract agar (MEA) and
its inability to grow on CYA supplemented with 5% salt and CYA and MEA incubated at
37 degrees C.