I have often written about Green Mould. My articles have probably been too long, I intend to be brief.
I have to conclude that growers who have an ongoing green mould problem are largely responsible for their losses
Do I hear a chorus of ‘well he would say that wouldn’t he’? At one stage I felt compost producers were primarily responsible for green mould problems, now I believe it is more likely to be primarily due to cross contamination, house to house, on farm. Some evidence is presented below, in two sections.
The general green mould situation with one particular compost maker
I looked in detail at the incidence of Trichoderma for 36 growers for virtually every ‘house’ filled in 1999-2002. They were all supplied by one compost maker (who I observe takes extreme hygiene precautions).
Overall, 20 percent of houses had at least a few affected bags. These showed the typical symptoms of green patches, either under the plastic, or on the casing, usually first visible between casing and cropping. Sometimes the green was accompanied by red-pepper mites. Sometimes there was little visible green-mould, just red pepper mites. In this case it is presumed that the mites had eaten most of the mycelium which would otherwise have produced green spores. Red pepper mites are carriers of green-mould spores.
Results showed a huge difference between growers
A few growers had ongoing problems with green mould in three quarters of the houses they filled. At the other extreme, a few growers had no green-mould. The growers who had most problems usually had lots of mites and were casual about dealing with them.
Both groups were getting the ‘same’ compost over a three-year period. Furthermore, when individual tunnels of compost were split between growers of the two types one tended to have Trichoderma problems the other didn’t.
A particularly satisfying advisory case!
A casing manufacturer and a different compost maker from that quoted above, both independently asked me to visit a grower who had had such a regular ongoing green-mould problem on blocks, that his supplier was threatening to quit supply.
I found the grower unusually energetic and receptive as regards applying the advice given below. Three months later he informs me he has only had green-mould in one of the last 7 houses and then only on 20 blocks, furthermore, yields have been quite exceptional! I congratulated him, he can now ease up a bit as he has probably broken the cycle of cross contamination. I agreed with his commitment to use a permanent ‘low temperature’ regime.
Formaldehyde ceased to be used as a disinfectant. This is because it tends to encourage Trichoderma. Prior to filling, hygiene levels were raised and mites were targeted. Any places they could lurk, such as in the tubing of racks and under the edges of the plastic house walls were sprayed with disinfectant, also all surfaces, including doors and door handles.
Dirty air ducts were replaced and these were washed at each fill
Great efforts were made to reduce dust at emptying and any possibilities of this or mites contaminating newly cleaned houses. The forklift transporting the blocks was sprayed and all surfaces likely to come in contact with newly arrived blocks were disinfected. No longer were blocks misted to keep them moist during spawn-run. Instead I suggested watering the floor to raise the humidity.
The men handling the blocks at filling wore clean disposable white ‘suits’.
Air temperatures were set at 22C maximum.
Ideally, block temperatures did not exceed 22C during a spawn run of around 19 days.
Blocks were only allowed to rise to 26C just prior to the cooling day when casing was applied.
Similarly, case run and cropping temperatures were also reduced.
