By Con Hermans, AdVisie ‘the mushroom growing consultants’, Heythuysen,
hermans@mushroomconsulting.nl
The silent killer returns PESTS AND DISEASES
In his role as a consultant, Con Hermans already noticed 20 years ago that the dangers of Virus X (MVX) were structurally underestimated. Now the mysterious virus is making another dangerous appearance, he calls for better monitoring, more research, and faster intervention to prevent worse. It’s time for a consolidated, sector-wide approach!
May 2003
Some 20 years ago, composting yards in the Netherlands and Belgium experienced a ‘light’ version of MVX. As they saw it as an ‘elusive and inexplicable’ problem, I was approached to investigate the issue from a practical perspective and come up with recommendations. I visited all the composting yards and analysed the problems as well as possible. In May 2003, I drafted the following hypothesis and recommendations: ‘It appears that MVX particles always occur in very low concentrations. Symptoms typical of MVX are not yet visi- ble. Re-infection can cause an increase in concentration. If other stress factors occur at the compost facility or on the mushroom farm, the typical MVX symptoms will become visible in that batch of compost. If the virus con- centration increases further, these stress factors are no longer needed as a trigger and symptoms will manifest at large groups of growers. If the concentration increases even higher, even more severe symptoms will occur, such as bare
patches.Do not underestimate MVX; coordinate Dutch and UK research; commercial varieties must be completely virus-free; investigate the risks of adding
spawnable compost to the compost to be pasteurised; strict hygiene throughout the tunnel process, transport and filling; no recycling of raw
materials; isolate farms with MVX; produce a vigorous compost; stimulate evaporation during growing; prevent stress factors’.
July 2018
Five years ago, I attempted to draw attention to MVX again. Some research had already been conducted into the associated ‘milder’ version, the Brown Cap Mushroom Virus that causes browning symptoms, but there was still practi- cally no knowledge of the bare patches. I stated my case in Mushroom Business:
‘Even for a consultant, things are not always immediately clear. The disease is always recognised as such too late and it can ultimately lead to a 60% drop in production. The virus can also initially put a consultant right off track, so you start looking for the root cause somewhere else. In my opinion, this virus is far more dangerous than Tricho- derma. You can see and identify Trichoderma and deal with it an early stage. By the time you actually see this virus, it’ s always far too late. The focus should be on taking preventive action’.
Again, there was a lukewarm response.. January 2023
Bare patch in 1st flush. 8 MUSHROOM BUSINESS
And now we arrive in 2023. The plant virology department at Wageningen University & Research is no longer able to accept new samples as they lack the capacity to test any more mushrooms for the presence of the virus. There have been cases in the Netherlands where virtually no mushrooms have appeared on the beds in the first flush, and the second flush was cooked out as a precautionary measure. The disastrous effect on production is perfectly obvious. The financial consequences are now extremely severe. And the situation I have been predicting for years is fast becoming reality. In January alone, mushroom growers from four different
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