Penicillium hermansii – Smoky mould
Smoky mould is a destructive compost infection first recognized in the Netherlands nearly 30 years ago. Despite being identified as various Penicillium species over the years, the true identity of the causal organism has only recently been confirmed through molecular analysis as Penicillium hermansii.
Penicillium species produce long chains of very small, lightweight, dry spores which are around 0.002mm in diameter (Fig. 1) and become airborne very easily. A single Penicillium colony (Fig. 2) will produce 400,000,000 spores per day. Although P. hermansii is very slow growing, it is problematic because of the large number of spores it produces and its short generation time. Penicillium hermansii will sporulate only three or four days after infection, producing thousands of daughter colonies which in turn sporulate rapidly.
