By Con Hermans, AdVisie
Compost under the weather COMPOST
Trichoderma keeps on rearing its ugly head. Even at compost yards in the Netherlands, where hygiene standards are high, green mould caused serious problems this year. Consultant Con Hermans visited several Dutch yards during the outbreak, and found there are other common factors causing the problems.
L
ast year, the majority of composting yards in the Netherlands experienced outbreaks of Trichoderma over a longer period of time. This green
mould has only been causing serious problems in the mushroom sector since 1984 when it mainly occurred in Ireland, the UK, Canada, North America, Mexico, and Columbia. Before that time, Trichoderma also occurred, but it was generally considered to be a sign of poorly fermented compost. In the Netherlands, these “foreign” Trichoderma problems were initially believed to be related to poor hygiene in the affected countries. However, the experiences of last summer beg the question of whether hygiene is the sole culprit. This article outlines some of my experiences in practice, which are by no means all scientifically substantiated. However, one thing I have learned in recent years is that it is better to rely on 90% certainty from practical experience than to keep waiting for 100% certainty from scientific research.
The biology of trichoderma. There are more than 460 different Trichoderma species, of which only a few are known in mushroom growing. These include Trichoderma harzianum,T. inhamatum,
T.virens,
T.viride, T. atrovire, and T koningii/T. pseudokoningii. Some of these species can only grow in casing soil and others only on mushroom stalks. The best known species that grew in compost was Trichoderma harzianum. However, it later turned out that were four different strains of harzianum and the classification was changed. The aggressive Trichoderma harzianum we currently see in mushroom growing is now called Trichoderma aggressivum and there are also two species of f. Aggressivium (Th4) and f. Europaeum (Th2). The presence of Aggressivium is feared in mushroom growing as it decimates crops and leads to 100% loss of production. In contrast, other agricultural sectors embrace Trichoderma harzianum as an ally that is widely used as a biological control agent to protect crops against
1) A Trichoderma colony inoculated (7 days ago) in the middle of some blades of spawna- ble compost does not develop further.
18 MUSHROOM BUSINESS
2) A small patch of Trichoderma on the beds is often underestimated. However, it can be the first sign of an imminent, more serious infection.
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