The following is a précis of the talks given. The objective was to provide a structured strategy to: assist in the formulation of a hygiene program and/or help solve a specific hygiene problem, to provide information to the owner/grower and identify the need to pass relevant information on to employees.
Disease Spores and Transfer Mechanisms:
The four most common disease problems discussed were: Verticillium, Mycogone, Dactylium and Trichoderma.
An infected mushroom could produce 30 million spores within an hour. Unfortunately these spores are not visible to the naked eye thus controlling the spread of disease is like fighting an invisible enemy.
During one talk Carl actually carried out his threat to smash into a bag of flour with a hammer to simulate the consequences of disturbing an infected mushroom. It was essential for everyone to appreciate the consequences of handling or disturbing an infected piece of disease. Whether disease spores were of the wind blown or sticky type, an understanding of the threat posed by each individual infection would enable common sense to be applied to all aspects of control.
Key Point: All employees need to understand that an infection is likely to generate millions of spores having a phenomenal potential to spread the problem elsewhere.
A spread vector was defined as any mechanism or activity that transferred disease. The most common spread is via disease spores.
External Spread Vectors Picture 6 above
Growers were asked to consider how could disease enter their unit via major and/or minor spread vectors?
Internal Spread Vectors Picture 5 above.
Growers were then asked to consider how could it spread once inside via major and/or minor spread vectors?
Checklist: People, materials, vehicles, operations, wind, dirt, flies and oneself.
Important Factors of Disease Spread and Counter Strategy
Stand back and objectively consider the possibilities. Keep it simple. Ask who or what comes onto the site occasionally or regularly. Watch the farm gate! Are they or it clean? Is there, or was there recently, a major transfer into the unit?
Once inside, disease can spread quite easily with very little effort! What and who moves around the site? Evaluate each part of the growing cycle. Evaluate each operator’s duties and the possible affect upon hygiene.
Start clean. Control and contain the (dirty) end of the growing cycle. Do not try to impose unrealistic “ideal” hygiene standards. Be practical and realistic instead, otherwise people will cut corners. Prioritise. Address the possible major transfer vectors first. Include, without going OTT, the prevention of the minor transfer methods into the standard or daily hygiene regime and discipline. Educate! If one has a problem, are there any patterns or clues?
Treat any infections promptly or else one infection becomes 10 becomes 100 becomes out of control!
Beware people, particularly harvesters. Disease grows on the mushrooms and they handle them!
Harvesters must not touch disease!
If there is no disease to touch they can’t. Treat disease before they visit the room. Once a piece of disease has been handled, the untreated hand is likely to transfer the problem most efficiently for the rest of the shift (and often for longer).
Beware growers: They apply water, a most efficient method of spread.
Do not water disease!
Whatever is gained in crop from watering will be lost in disease increase. If one must water, treat the disease effectively first.
Beware flies: They have not read nor have any consideration for the hygiene manual.
Get rid of the flies!
If you have a significant fly problem they will simply sabotage your best efforts to prevent spread.
Treat disease carefully and properly!
Beware of spot treatment: Are you treating or spreading? This must be done carefully. It is extremely difficult to treat infections without actually spreading it.
Beware at end of crop: Poor hygiene at the end of crop can be disastrous.
Empty cleanly!
Kill before emptying. It is culturally suicidal not to do so. If one diseased mushroom has the potential described earlier to spread disease – what potential a whole house of dirty beds? Often untreated whole houses are thrown carelessly onto trailers.
Also consider: Air currents – wind, isolation of operations, filtration. Note that spores tend to eventually fall onto floors! People: clothing, hands etc. Does Mary always wear that favourite cardigan? Are the operators on the “clean” jobs themselves clean? Is all equipment clean? Is there a standard cleaning procedure? Are materials such as compost and casing clean? The hygiene program should be cost effective. Prevention is better and cheaper than treatment. Have you provided adequate training? If the problem is becoming out of hand – cut your losses.
Key point: Apply common sense to all of the above taking into account the points made earlier regarding ease of spore transfer from an untreated infection.
Further Discussion on Specific Operations and Issues:
Trichoderma: Certainly tackle the problem at source but also avoid any operation that stirs/mixes/aggravates/carries over the infection.
Spot Treatment: The excellent video “Practical Hygiene, zero tolerance in disease control” by the IMGA makes the point that hard work put into a program can be wasted if the program is incomplete i.e. there are holes in the strategy. This video also includes advice on safe spot treatment to beds without actually increasing the spread of spores. This uses a damp tissue and salt. Whatever method is used, the application of salt or other liquid must be done very carefully to avoid making things worse. Staff treating disease must be fully trained. Are they interested and caring? If they are not, forget it! One should treat all houses before harvesting and watering, however, if any pieces are discovered later, they may be flagged and avoided.
Flies: They can breed fast and multiply greatly in numbers thus it is thus not surprising, if populations are allowed to get out of control, it is difficult to recover the situation. Start preventative treatment promptly each season before significant numbers are seen. Don’t wait until you see you have a problem. Flies do not read and adhere to hygiene instructions nor dip their feet. If fly numbers are significant, prospects for disease control are minimal.
End of crop sterilisation: The removal of old crops, if infected with disease, is one of the most difficult operations to complete truly hygienically. Crops must be sterilised before removal. If not, the manhandling and disturbance to any disease present will release an unimaginable number of spores that will be readily distributed all over the farm. Has anyone ever Hoovered the family house and then emptied the dust bag, swinging it around one’s head in the living room? This is a somewhat dubious analogy but the consequences would be similar.
Cathal Ellis gave a detailed account of the most effective temperature regimes for the steam sterilisation at end of crop. 68C at the top of the compost for 8 hours was most effective but could be impaired by compost inactivity preventing this temperature being achieved.
Martin Duffy detailed fly breeding cycles and the numbers involved, also on available chemicals, application and safe working.
Are you doing what you think you are doing?
Whatever treatments or operations you have – take another close look and check that what you think or hope is happening – really is - and accurately.
Do the others know what they are doing?
It is insufficient for the grower/owner alone to understand the basics of good hygiene. When did you last ensure everyone was fully trained in the principles of hygiene and understood the critical factors to their own individual jobs?
Key point: Many of the points discussed above are likely to be already familiar to experienced growers. It is stressed however that this experience is of limited value if not passed onto employees. All staff must have a good understanding particularly of the potential for disease spread and of the part that they play in maintaining an effective hygiene program. Training to this end needs only to be simple to be effective.
Closing Summary:
If nothing else, remember the demonstration with the bag of flour! - the main spread mechanisms: harvesters, watering, flies - treat the early pieces promptly – check what you think you are doing – empty cleanly – make sure the others know what they are doing.
Comment:
Note that the most common cause of problems on some farms visited during the week of the talks was seen to be early pieces of disease NOT being treated promptly.
