Control of Trichoderma Green Moulds
One of the most serious production problems that affects mushroom cultivation is that caused by competitor and pathogenic green moulds (Trichoderma species). Of these, the aptly named Trichoderma aggressivum has caused the most serious button mushroom yield and quality losses. So far, a European form, T. aggressivum f. europeum, has been responsible for large crop losses in the UK, whereas a different form, T. aggressivum f. aggressivum, has caused devastating crop losses in North America, and this also remains a continuous threat to the UK. Green moulds are also a serious problem in the cultivation of other types of edible fungi, including oyster mushrooms (Pleurotus species) and shiitake (Lentinula edodes). If substrates used for growing mushrooms become contaminated with green mould spores or mycelium, the mushroom mycelium is rapidly out-competed for nutrients and infected fruitbodies become spotted and unmarketable. Characteristic of Trichoderma species are small resilient green spores with sticky surfaces which enable them to be easily spread around the farm on air currents, flies, pickers and equipment. The withdrawal of formaldeyde as a gaseous disinfectant and of caustic chemicals for dipping wooden growing trays has been a particular problem for farms without the facility to steam clean rooms at the end of each growing cycle. Research at EMR is identifying the environmental conditions needed to eradicate green mould inoculum during the preparation of the compost so that it is safe to grow mushrooms. The research is also comparing the efficacy of permitted disinfectants in killing inoculum of a range of Trichoderma species, so that the best products are used for sanitising mushroom farms.