Trichoderma harzianum is becoming a problem in more and more countries. Sometimes it remains limited to a single tunnel, but in other situations it can develop into a complete catastrophe where entire tunnel companies and mushroom farms are heavily infected and production falls to less than 10 kilos per square metre over a longer period. Once Trichoderma has been detected, serious measures must be taken to combat the infection. As always prevention is better than cure.
One of the most vital steps is observing strict hygiene during inoculation. An equally important aspect but one often paid too little attention is the ammonia concentration during pasteurisation. Effective pasteurisation is a combination of temperature time and ammonia concentration. If the ammonia concentration is too low, there is a much higher risk of Trichoderma infection. To help avoid this it's better to make nitrogen-rich phase 1 compost. If however compost with a low ammonia concentration is filled in the tunnels, increase the pasteurisation time by a few hours.
Con Hermans, AdVisie ‘The mushroom cultivation advisors’