Colonisation of phase II compost by biotypes of Trichoderma harzianum and their effect on mushroom yield and quality

Colonisation assessments confirmed that Trichoderma harzianum biotypes Th1, Th2a, Th2b and Th3 inoculated into two distinct compost types at spawning became established by first flush assessment; the extension rate of two Th2 isolates was over 1000 times that of Th1 and Th3. Results subsequently confirmed that while Th1 and Th3 did not significantly affect yield, Th2 could reduce mushroom quality and productivity by as much as 80%. Analysis of compost type also indicated that the speed and magnitude of T. harzianum colonisation was influenced by key compost characteristics, most notably, moisture, ash content and degree of fermentation. This study has shown that compost parameters which have a positive influence on Agaricus growth and productivity also resulted in increased compost colonisation by T. harzianum. Commercially acceptable yields obtained from uninoculated compost confirmed that production of a high quality, productive substrate does not confer inherent immunity to colonisation by T. harzianum. Received: 25 September 1998 / Received revision: 30 November 1998 / Accepted: 5 December 1998