CULTIVATIONTIPS ADVISIE Bacterial blotch – too dry or too wet? Door Jos Hilkens
AdVisie ‘de champignonteelt- adviseur’, Herkenbosch
hilkens@champignonadvies.nl
The causal agent of bacterial blotch, the Pseudomonas tolaasii bacteria, is always present on casing soil and often on the mushrooms too. In the right conditions, the bacteria will develop at astonishing speed and brown blotches will become visible on the mushrooms within a few hours. Most of the blotches are pale brown, shiny and feel sticky to touch. Other symptoms are small, indented spots that are often confused with green mould infection on the caps. Undisturbed growth and the associated constant evaporation are crucial to prevent problems. With the current, greatly fluctuating moisture content of the outside air, huge differences between the day and night time temperature and less active compost in the second and third flushes, alertness and a rapid response to these changes is vital. Bacterial blotch tends to occur faster on wetter compost and casing soil, with too little evaporation or misting or condensation forming on the casing soil. But in practice you sometimes see the opposite - that a too intense and long period of drying has followed a spraying session. So choose carefully, too wet or too dry, and then adjust the climate settings accordingly. A lower CO2, minimum air inlet position and lower RH often provide the solution.
The trap is the weakest link Door Con Hermans
AdVisie ‘de champignonteelt- adviseur’, Heythuysen
hermans@champignonadvies.nl Photos: AdVisie
Tunnel companies that supply incubated compost know just how vital good hygiene is. Compost is made as selective as possible, but before the compost has been fully colo- nised with mycelium competitor moulds can seize their chance and gain a head start, with disastrous consequences. Anyone who has been faced with infection at tunnel level is aware of the negative financial impact this can have and will do everything to prevent this occurring. A lot of time and money is devoted to hygiene. All the incoming air for the tunnels and inoculation area is filtered using high efficiency spore filters. Negative pres- sure is applied in the ducting between the filter and the fan. Even if there is the tiniest of leaks in this part of the climate unit, unfiltered air will be sucked in and all the invest- ments made in inlet filters and other hygiene measures will be largely cancelled out. Condensation occurs in the climate units, which has to be drained off. This is usually done via a trap. This trap must prevent any unfiltered air being sucked into the installation via the trap. The trap installation is often the weak link in the system and is frequently prone to problems. If the water column in the trap is too shallow, it will be sucked dry. If there is a rupture, water will not flow in or out of the trap. An extra risk is present in situations where a central condensation drain system is used whereby the traps in the tunnels are all connected to the drain. If the traps do not function properly an open passage is crea- ted between the tunnels. And as experience teaches, this can lead to huge problems. The lesson is to regularly inspect the climate unit and particularly the traps. Installing transparent, plexiglass traps will show you if they are working properly.
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Jos Hilkens +31(0)653 31 6204
6 MUSHROOM BUSINESS
Con Hermans +31(0)653 29 9396
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