14) Trichoderma in a sealed block of phase II compost.
15) The contents of this severely infected tunnel should not be supplied.
a place to survive. The blocks from this spawning tunnel were supplied in blocks but imagine what would happen if spawning was done in a phase III tunnel. In this scenario, the patches contaminated by Trichoderma would be mixed repeatedly through the compost - at spawning, when the tunnel was emptied, when the trailer was loaded - and finally when the beds were filled at the mushroom farm. And you guessed it; just a few patches can cause a severely infected tunnel (photo 15)!
Ammonia I believe that the ammonia concentration is far more important than the temperature during pasteurisation. That is also a lesson learned by growers in the past. Compost had to smell pungently of ammonia when it was filled in the pasteurisation hall as a protection against Trichoderma. I gained this experience another way. I was asked to analyse the Trichoderma problems affecting a large company that filled hundreds of tunnels a year. Their hygiene standards seemed to be fine. I reviewed the ammonia data measured in the pasteurisation peak in all the tunnels of the past year. This quickly revealed what the issue was. Tunnels with ammonia levels higher than 400 ppm during pasteurisation hardly ever had problems with Trichoderma, tunnels with lower than 100 ppm practically all had problems with Tricho- derma and tunnels with approximately 250 ppm sometimes experienced problems. This led me to conclude that ammonia is more important than the temperature. In my view, pasteurisation is only effective with 8 hours of pasteurisation at an inlet air temperature of 56°C with an ammonia concentration of 400 ppm. The ammonia concentration should be at
least 250 ppm. For every 100 ppm lower than the target value of 400 ppm, extend pasteurisation for an additional hour. It is precisely the ammonia concentration that makes the difference during pasteurisation, but also during cook-out. This is most likely why cook-out for 20 hours at 60-65°C in a growing room does not destroy Trichoderma - there is no ammonia present. It also explains why dry patches in the compost are so dangerous: ammonia dissolves easily in water, but dry patches lack the moisture to bind ammonia so it is blown though the compost. Cook-out in empty tunnels at 70°C is also more effective with ammonia and for this reason some tunnel companies evaporate urea in the tunnel during cook-out.
Approach in the future I do not actually believe that Trichoderma is currently the most dangerous threat in mushroom growing. Trichoderma remains a disease with an enormous impact and sometimes catastrophic consequences that is increasingly difficult to control, partly because the use of fungicides is banned. However: Trichoderma is easy to identify, can be quickly detected, is an enemy we know how to manage and the results are noticeable. I think Virus X is a far bigger threat: much less is known about this disease, it is always detected too late and before you realise, it has infected the entire company and caused considerable economic damage. The sector should carefully consider permitting the temporary use of fungicide - on prescription - if a composting yard is facing a persistent outbreak of Trichoderma. Spawn producers could also play a role by investigating whether it is possible to coat spawn to protect it against Trichoderma infection.
MUSHROOM BUSINESS 25
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