A perilous tan.

It isn't often in my line of work that I come across something completely different. I visit many farms and have seen about as much as there is to see, but rarely do I find something really unusual. Of course there are the useful little changes and ideas that individuals identify as their own with respect to a cultural technique. Sometimes I come across mechanical modifications or operational procedures that achieve a common objective in a different and more effective manner. However, when I was working in the United Kingdom (UK) and Ireland years ago I came across a situation that was totally unique.

It was a condition on a particular farm where a certain percentage of mushrooms grew with a slight tan or very light brown cast to the mushrooms of an off-white strain. Later I came to know this same problem appeared on a few other very small sites in the same general area. The affected mushrooms were of a reasonable quality and would grow among other perfectly normal white mushrooms except for the unfortunate fact that they were tan. Although the patch (Virus X) condition was running rampant though the UK at the same time, I did not associate the condition with Virus X at that moment, although I really did not have a definitive answer on what the causative agent actually was. The condition got progressively worse on the farm and much later it was associated within the Virus X group of diseases since some double stranded RNA was found in the affected mushrooms. To this day there is still disagreement whether the tan mushroom symptom is really considered a definite expression of Virus X.

Well that was about eight years ago and outside of the small cluster of farms in the UK that had this condition, no other farms reported having it. That is until just recently. I visited a farm in Australia that was battling some mysterious discoloration condition on their mushrooms. Entering the farm on the first day of the visit I had an immediate flashback--the tan mushroom syndrome I had seen in England. Not wanting to commit immediately, I continued upon a course of due diligence for the better part of the day.

Here's what I saw. Tan mushrooms growing right next to normal brilliant white ones. The tan mushrooms had a somewhat corky texture and stem trim met with more resistance that normal ones. Tan mushrooms that were slightly more mature gave the impression that they were dying on the shelf since gill coloration was dark and showed a slightly mummified skin texture. The condition was getting progressively worse, effecting a higher percentage of mushrooms. Initially the condition was seen in later breaks but had progressed to the first break and some rooms were better than or worse than others. Finally, significant yield decreases were just starting to be realized. After several hours of investigation I found nothing else in the cultural system that might create the tan discoloration so I presented the grower with my assessment. My conclusion was that the problem was virus due to my previous experience and the appearance that the mushrooms were actually dying on the shelves due to some systemic trauma. From there we started the task of isolation, identification and remediation.

In isolation we initiated a series of trials and experiments where we tried to disprove every other possibility that had been tabled to that point. We trialed possible causative factors such as airflow, supplementation, chemical application, compost, selective blotch sensitivity and watering practices to create or eliminate the condition by changing some cultural practice.

Simultaneously we sent off samples to Helen Grogan and Pete Romaine for La France and Virus X analysis as well as other possibilities. Prior to this the owner had sent off samples to the Australian lab and Penn State only for La France virus and they proved to be negative. It is important to note that during the Virus X outbreak in the UK, La France virus analysis did not recognize Virus X infection because of its extreme virulence (low number of virus particles required to show significant symptoms).

Finally we set about making procedural, clean up, sanitation/hygiene, harvesting and filtration changes to contain the virus where it was and eliminate the possibility of transfer to new or "clean" crops. Extreme virus control (and therefore any infectious disease possibility) measures were instituted to reverse the trend that had already marginalized the farm's reputation as a quality supplier as well as a 20 percent reduction in total production.

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Since my visit, I have been in contact with the owner to assess progress against the problem and although things are getting better, they are still not great. Additionally, some prominent individuals in the world of mushroom culture have suggested other theories. These have been pursued to eliminate all possibilities since the objective is not being right; it is to eliminate the problem from the farm. Unfortunately no other proposal has eliminated the condition. To further the frustration, our original isolation and identification initiatives have not been totally conclusive. The isolation trials were successful because they proved that we could not increase or decrease expression by only adopting other cultural techniques. The results from identification samples are mixed. Before the possibility of dealing with a virus was known, La France analyses came back negative, while after the suspicions were raised some samples came back positive for La France. Although historically the tan symptom had some association with Virus X, the samples for Virus X testing came back negative.

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The only reasonably correlation that seems to work is that by adopting extreme hygiene and virus control measures, disease incidence has decreased but has not been eliminated. The company continues to plug away at elimination of the symptom via the original and updated virus control measures. I look forward to my next visit to evaluate progress and offer further suggestions.

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I guess the moral of the story is always keep an open mind. No matter now mundane and routine things get on a mushroom farm there is always the possibility that something new and unique and different may raise its head--and more times than not it is an ugly head.

Ray Samp 

Agari-Culture

Consulting Services

113 Colleen Court

San Marcos, Texas 

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"Spore Prints" is a regular column featuring conferences around the world, market situations in various countries, alternative raw materials, introduction of mushroom personalities, historical perspectives of industry trends, farm management and personal opinions. Ray Samp can be reached at Agari-Culture Consulting Services located in San Marcos, TX, email: [e-mail]