Biosecurity and plant hygiene

[Phil Rabl]

BACKGROUND
In December 2021, the Ballarat Botanical Gardens introduced new and more stringent biosecurity rules for groups such as the Ballarat Bonsai Society which bring plant material into the Gardens’ precinct. This caused me to think systematically about best practice for bonsai artists from the perspective of biosecurity, or plant hygiene. What should we do? What should we not do?

This led me to develop the following information in consultation with members of the three bonsai clubs I belong to: Ballarat, Canberra and the Victorian Native Bonsai Club. All three of these clubs have, or about to, publish the information in their newsletters.
Now I know (including from some comments posted on AusBonsai) that some bonsai artists think this is “a load of crap”. But it is pretty serious.

So I, and the three clubs I am a member of, encourage the Executives of other bonsai clubs to consider adopting the following advice (modified as you see fit to meet local needs) for the benefit of your members and the health of your members’ trees.

BIOSECURITY: A NATIONAL PRIORITY
Plant Health Australia is the national coordinator of government-industry partnerships for plant biosecurity in Australia. Over 40 industry organisations affiliated with Plant Health Australia have developed biosecurity plans. While a key focus of these plans is minimising the biosecurity risks posed by insects, pathogens and diseases (collectively called pests) that are new to Australia, they contain a lot of useful information relevant to the management of pests and diseases in our domestic bonsai collections. Because pot culture is so central to nursery industry operations, the Industry Biosecurity Plan for the Nursery Industry is the most relevant to the bonsai community.

PLANT HYGIENE: A BONSAI PRIORITY
Plant hygiene is a major priority for bonsai clubs and individual bonsai artists, and it presents some complex challenges. It is essential to have measures designed to prevent the transmission of pests and diseases as bonsai artists move plants from their own collection to meetings, shows, workshops, markets and sensitive sites such as botanic gardens.
To meet these challenges, it is important for clubs and individual growers to have appropriate practices for, at least, each of the following four situations:

• 1. Trees in a grower’s own collection, at their home location.
  2. Trees brought to a bonsai club meeting.
  3. Bonsai club public exhibitions.
  4. Bonsai displays in sensitive places, such as botanical gardens.

Plant hygiene advice for each of these situations is provided below. Note: This paper uses the term ‘pests’ in the same sense as Plant Health Australia: insects, pathogens and diseases that may pose plant hygiene risks for our bonsai are covered by the collective term ‘pest’.

A PLANT HYGIENE WINDOW INTO BONSAI PRACTICES

1. Trees in a grower’s own collection, at their home location
Every bonsai artist has a direct vested interest in keeping pests under control in their own collections. This is easier said than done. The pests to which our trees are susceptible will vary from location to location and the differing conditions under which we each operate in our own spaces, often mixed in with other garden settings, also changes some risk factors.

The following summarises a range of relatively routine bonsai activities or events that occur in our back yards, along with suggested plant hygiene steps to protect our bonsai collection in their home locations.

Event/activity and Suggested plant hygiene practices
You acquire new plant.
• As far as possible, store the new plant away from your other trees until you are sure it is pest-free.
• The length of time these plants should spend in a quarantine zone depends partly on their source. You are more likely to be familiar with possible pests on a locally sourced tree, but less likely to know what to look out for on one sourced from beyond your local region.
• Note that Australian plants that are native to regions distant from your location will often suffer badly from locally occurring pests.
• Monitor the tree closely for pests until you are comfortable your new acquisition is pest-free.

You dig tree from your garden or open space (yamadori)
• Remove as much soil as is possible/safe to do before potting up.
• As far as possible, store the new plant away from your other trees until you are sure it is pest-free.
• Monitor the tree closely for pests.
• Remove more soil each re-potting until the tree is growing in 100% bonsai potting mix. Note that most collected material will retain some of the original soil even after a long period of time and frequent repotting. Note too that the longer you have a healthy yamadori, the less likely it is that any remaining soil contains pathogens of concern.
• Note that some botanical gardens, ban yamadori because they do not permit any soil in potting mixes.

Re-potting
• Always clean and disinfect your bonsai pot, even if the tree is going back into the same pot.
o ABC gardening suggests using one-part household disinfectant to 20 parts water.
o Some suggest using one-part domestic bleach to 10-15 parts water.
o Others recommend standing your pots in full sun for as long as possible before being reused.
• It is best not to recycle potting mix. If you do recycle any components that do not deteriorate (such as zeolite) be aware that you are increasing the risk of passing soil pathogens among your trees. It is strongly recommended that any recycled components are left in full sun for as long as possible before being reused.
• Dispose of deteriorated plastic pots.

Routine trimming, pruning or carving
• Always clean and disinfect your tools before starting on a different tree.
• Consider using two sets of tools. ABC gardening suggests sitting the spare set in a container of a solution of one-part household disinfectant to 20 parts water.
• Bag and dispose of any trimmings from trees with pests.

Watering
• From time to time, it can be necessary to water trees by dunking them in a container. It is bad practice, however, to dunk multiple trees in a common tub. Doing so greatly increases the risk of passing soil pathogens among your trees.
• Watering in the morning helps reduce the risk of mildews, rust and scab, which can spread more readily on wet leaves during the evening.

2. Trees brought to a bonsai club meeting

At club meetings, plant hygiene has both an individual and a club component.

While recognising that it is impossible for bonsai clubs to guarantee a pest-free setting at club meetings, it is quite legitimate for club rules to place expectations on members to ensure the plants they bring to meetings are pest free.

Regardless of whether or not the club has adopted such rules, individual members bringing trees to a meeting have a duty of care to other members to ensure that, as far as possible, there are no pests on their plants that would put others’ plants at risk.

Component and Suggested plant hygiene practices

Club
• Club rules should make it clear that it has the authority to require a tree with pests to be removed from the meeting.
• Clubs should develop pest management information for members so they can educate themselves on good pest management practices.
• Clubs should advise members to adopt sound plant hygiene practices along the lines of those set out in part 1., above ‘Trees within a grower’s own collection, at their home location’.

Individual
• Members should inspect their trees prior to bringing them to a club meeting to ensure they do not harbour visible pests.
• Members should adopt sound plant hygiene practices along the lines of those set out in part 1., above ‘Trees within a grower’s own collection, at their home location’.

3. Bonsai club public exhibitions

Because trees displayed at bonsai club exhibitions are members’ higher quality trees, the consequences of spreading pests from tree to tree of are likely to be more serious than at less formal gatherings such as club meetings or workshops. The plant hygiene principles are, however, the same.

Component and Suggested plant hygiene practices

Club
• Club rules should make it clear that it has the authority to require a tree with pests to be barred or removed from the exhibition.
• Exhibition organisers should advise members of any plant hygiene requirements they must meet to participate in the exhibition. E.g., that the tree has no visible pests and a reminder that members are expected to follow sound plant hygiene practices along the lines of those set out in part 1., above ‘Trees within a grower’s own collection, at their home location’.

Individual
• Members should inspect their trees prior to bringing them to an exhibition to ensure they do not harbour visible pests.
• Members should adopt sound plant hygiene practices along the lines of those set out in part 1., above ‘Trees within a grower’s own collection, at their home location’.

4. Bonsai displays in sensitive places, such as botanical gardens

Facilities that host bonsai exhibitions may have rules that participating clubs and/or individuals must abide by. If a botanical gardens is the hosting facility, the plant hygiene requirements may well be more stringent than for non-botanical facilities.

From the perspective of bonsai clubs and individual bonsai artists, however, the plant hygiene principles are the same.

Component and Suggested plant hygiene practices

Facility
• It is the host facility’s prerogative to set plant hygiene requirements that users must adhered to. This could include inspections and/or other evidence that plants being brought in are pest free; a ban on soil in the potting media (this could entail a ban on yamadori); bagging and removing any trimmings; and entering and exiting the facility by the shortest possible route.
• Note: Biosecurity plays a very important role in the acceptance of both loan and donation trees and plants at the National Bonsai and Penjing Collection of Australia (NBPCA).
o When a tree is approved for either loan or donation, the lender or donor is instructed to apply topical general pesticide and fungicide treatments to both the foliage and the root system.
o Prior to transport, each tree is inspected for any evidence of pest or disease. Once the tree or plant has arrived at the NBPCA, it is quarantined for a period of 2 weeks to ensure no emergence of pest or disease.

Club
• Clubs need to have a clear understanding of the plant hygiene requirements of the host facility and agree to adhere to them in detail or meet them through other agreed standards. The facility’s rules would need to be ascertained in advance so that any necessary negotiations can be concluded in time to inform members of the requirements.
• Club rules should make it clear that it has the authority to require a tree that does not meet the facility’s requirements to be barred or removed from the exhibition.
• Exhibition organisers should advise members of any plant hygiene requirements they must meet to participate in the exhibition.
• As part of any negotiations with the host facility, clubs might find it beneficial to be able to demonstrate that its members follow the sound plant hygiene practices set out in part 1., above ‘Trees within a grower’s own collection, at their home location’.

Individual
• Members should inspect their trees prior to bringing them to an exhibition to ensure they do not harbour visible pests.
• Members should adopt sound plant hygiene practices along the lines of those set out in part 1., above ‘Trees within a grower’s own collection, at their home location’.

PEST MANAGEMENT GUIDANCE

Leaves shows signs of pest infestation. What should I do?

This can be complicated. The following table identifies some symptoms you might see and some possible causes and remedial actions.

Observation and Possible cause/action
If the leaves on one of your trees change colour unexpectedly
• Consider the possibility of sun damage.
• Check for over/under watering.
• Check for sap-sucking insects.
• Consider what diseases is the species susceptible to.

If the leaves on one of your trees become disfigured
• Check for over/under watering.
• Check for leaf-eating grubs/caterpillars or insects.
• Consider what diseases is the species susceptible to.

If the leaves on one of your trees droop
• Check for over/under watering.
• Consider whether root damage a possibility. Check for curl grubs, nematodes, gall, root aphid.
• Consider what diseases is the species susceptible to.

If you notice an insect infestation on one or more of your trees
• Note that some infestations need to be treated, others do not.
• Check for scale, mites, aphids, thrips, grubs/caterpillars.
• Follow the instructions for chemical, biological and cultural controls.
• Harmless visitors (e.g., a few spiders or lady bugs) should not be killed.
• Check for fungal infections.
• Consider if sun damage a possibility.

What causes leaves to change colour or texture?

Except for normal seasonal changes in leaf colour, most notably in deciduous trees, changes in leaf colour or texture should always be investigated. It should be noted though, that there are numerous reasons for evergreen foliage to change colour or texture, and not all of them are due to the presence of pests. E.g.:
• Lack of water. Even a short spell of drying out can damage evergreen foliage, but the damage may not show up for several weeks. This can make it difficult to remember when you forgot to water.
• Not enough light. Plants need sunlight for photosynthesis, the process by which plants create energy in the form of sugar (plant food). Leaves that do not get enough light for photosynthesis will weaken and eventually die. Inner and lower leaves are most likely to be affected because they tend to get less sunlight.
• Pests. Pests such as mites can cause a lot of damage to leaves. Mites are tiny sucking insects, barely visible but they can breed prolifically and suck enough sap out of the leaves to kill some.
• Old foliage dies naturally. All leaves have a finite lifespan. Evergreen leaves typically live for 2-3 years then die while newer leaves take over. Leaf discolouration may be part of the natural lifecycle.
• Starvation. When nutrients are scarce, some leaves can die. The location of the nutrient-deprived leaves will depend what nutrients are most lacking but older, inner leaves are often the most affected.
• Physical damage. Even if physical damage is not visible, a branch will die if sap flow is restricted or stopped. Animals and accidents can damage trees. So too can less obvious events such as over-zealous bending, which may not show up until a few weeks after the wiring and bending interrupted the sap flow.
• Too much water. The visible signs of too much water can be the same as too little water. When the roots are constantly too wet, they can rot. If this happens, the tree will not get enough water even though the soil is wet.
• Oversupply of a nutrient. An oversupply of one element (nutrient) can make another element unavailable to the plant (even though it is present in the soil).

What pests should I be on the lookout for?

As mentioned above, Plant Health Australia uses the term ‘pests’ to cover insects, pathogens and diseases that pose biosecurity risks. This paper uses the term ‘pests’ in the same sense: insects, pathogens and diseases that may pose plant hygiene risks for our bonsai are covered by the collective term ‘pest’.

It can be very complicated to accurately identify pests and to know to what to do about them. And it is not possible for anyone to know everything, a reality that is made very clear from the categories of pests identified by the Industry Biosecurity Plan for the Nursery Industry:
• Bacteria.
• Bugs - stink bugs, aphids, mealybugs, scale, whiteflies and hoppers (Hemiptera).
• Flies and Midges (Diptera).
• Fungi.
• Ants and wasps (Hymenoptera).
• Butterflies and moths (Lepidoptera).
• Snails and slugs (Gastropoda).
• Mites e.g., spider and gall mites (Acari).
• Nematodes.
• Thrips (Thysanoptera).
• Viruses.

Does my tree have any pests? If so, is it a risk to other trees?

These are important questions, but they can only be answered on a case-by-case basis and require an understanding of which pests can attack which species and what pests are endemic to which location – knowledge that most bonsai artists will not have.

Pest and disease information sheets
Ideally, the above guidance would be supported by Pest and Disease Information Sheets relevant to the local area. BBS, CBS and VNBC have developed some Pest and Disease Information Sheets. If clubs have an interest in sharing their knowledge and techniques for managing pests and diseases, please say so in posts on this article.

[Rory]

Most of this is just generalizations and scientifically speaking, it’s not going to be effective when looking at the issue as a whole.

Take the coronavirus for example. We all knew the exact science of how to kill it and how to minimize the spread. But eventually in the real world, nature will dictate the outcome.

[KIRKY]

Where is the yawn emoji??? ………. Never the emoji you need!

We are already an Island with isolated states that have their own interstate Biosecurity in place.
All these plant pest, infestation you are talking about can be on things like your boots, shoes, clothing the air that you are breathing. Blowing over the fence from your neighbours like the weed killers they spray. Blowing in the wind from one state to another. Are you therefore suggesting we bring a change of clothes, shoes, boots to every venue we visit too? Should we all have a sterilisation shower before entering the Botanical garden, Bonsai clubs, shows, nurseries. Or are you expecting we live in a bubble. (Been there done that for nearly two years down here. Really didn’t like it!)
There are spores and pests you breath in everyday that you are not even aware you are breathing in. (Yes Rory covid is one of them ) Just because they aren’t harming you or your trees doesn’t mean they aren’t there.
There is such a thing as toooooooooooo much red tape and b s.
Cheers
Kirky

[treeman]

In the early days (20s 30s 40s 50,60s) plant material was freely imported into AU. I remember stories of cases of orchids from south east Asia (for example) ripped out of the Jungle and send directly to AU and (EU USA Japan etc) without cleaning, without ''inspection'' and without restriction.
The result? Lots of nice plants to grow. Where are all the devastating pests and diseases? Nowhere to be seen. All the maple, pines, junipers, cedars, Liquidambars, oaks, Camellias, azaleas, rhododendrons, all kinds of annual and perennial flowers, lawn grasses, vegetables, cereal grains where all imported into into Australia without restriction 100 years ago. Where are all the devastating pests and diseases? Nowhere to be seen. Those that are here are all easily managed and certainly do not pose a major threat.
The result is a thriving agricultural and horticultural industry of world class.
The quarantine ''industry'' in this country is in the main, a bloated, over-regulated and usually unnecessary waste of time promoted by rent-seeking people in self-proclaimed authority desperate to justify their existence. Most of them have no idea what they are looking at when it arrives, or how to treat it, and don't care the slightest about whether it lives or dies under their ''watch''. As long as they get their unjustified and exorbitant price for the ''service''. They have done a good job however, of scaring the bejeezus out of the gullible, ignorant policy makers with stories of post apocalyptic wastelands should we not follow their sage advice. How long ago was it when they would walk down the isle of a newly landed plane fumigating everyone with spray cans? Lunatics!
Australia is regarded as a bit of a joke to plant growers and sellers in most other countries around the world.

[TimS]

In the early days (20s 30s 40s 50,60s) plant material was freely imported into AU. I remember stories of cases of orchids from south east Asia (for example) ripped out of the Jungle and send directly to AU and (EU USA Japan etc) without cleaning, without ''inspection'' and without restriction.
The result? Lots of nice plants to grow. Where are all the devastating pests and diseases? Nowhere to be seen. All the maple, pines, junipers, cedars, Liquidambars, oaks, Camellias, azaleas, rhododendrons, all kinds of annual and perennial flowers, lawn grasses, vegetables, cereal grains where all imported into into Australia without restriction 100 years ago. Where are all the devastating pests and diseases? Nowhere to be seen. Those that are here are all easily managed and certainly do not pose a major threat.
The result is a thriving agricultural and horticultural industry of world class.
The quarantine ''industry'' in this country is in the main, a bloated, over-regulated and usually unnecessary waste of time promoted by rent-seeking people in self-proclaimed authority desperate to justify their existence. Most of them have no idea what they are looking at when it arrives, or how to treat it, and don't care the slightest about whether it lives or dies under their ''watch''. As long as they get their unjustified and exorbitant price for the ''service''. They have done a good job however, of scaring the bejeezus out of the gullible, ignorant policy makers with stories of post apocalyptic wastelands should we not follow their sage advice.
Australia is regarded as a bit of a joke to plant growers and sellers in most other countries around the world.

Working with biosecurity plant material coming in from around the world every day…….there is no lie in any of what you just said.

When we had visitors from the sister companies overseas before Covid, they could not believe the governmental restrictions and hoops we have to jump through here with importing plant material.

Having said that there are many pests and diseases better kept out of the country if we can avoid it

[Matt S]

From a club perspective, getting basic hygiene practices down on paper is a important. As president of the SA Bonsai Society I can tell you we've had many instances of people bringing in trees with obvious signs of pathogens which we have asked them to remove. We have a duty of care for all our members trees and because we have it stated in our constitution we can point this out to people if they arc up about it, and it does happen. For our annual show, trees for sale are inspected. We can't catch everything but trees with scale, signs of virus infection or redback spiders under the pot lids are handed back before they are sold to the public.
This all needs to be written down somewhere rather than rely on word of mouth or peoples good intentions. If we hold an event somewhere, we need to be aware of the rules of the host location. When we organise digs in parks, we follow the requests to spray our boots and tools beforehand. Will we prevent all pests from spreading? Of course not, but that doesn't mean we do nothing.

I hope that makes sense!

Matt.

[Oliver E]

Wow, I'm so disappointed in the negatively dropped on this post.
It is a basic outline of health and hygiene, with some common sense courtesy.
Its best practice and sure best practice is not always practical or possible, but it's good to aim for. I wish I had better discipline some times.
Thanks Phil, don't let the negatively Nancys get you down.

[TimS]

It comes down to situation for me.

If you are taking material into a business (production nursery if you have club days there/ NBPCA/ etc) then it is highly likely they will have some plan in place themselves to protect the company. Where I work the rule is no material from your home may be on site. Not because there is some magic pest or diseases that hasn’t been found at the nursery before but is 20km away in my back garden, but because it saves headaches of having more than is already here turning up.

In preparation for a show a logical thing to do would be to treat your trees for pests/ disease, both as a courtesy to other people but also because who wants to display a tree covered in pests!? So that takes care of the show scenario.

At club meetings it would be hard to stamp it out because the hobbyist who is new and isn’t familiar with problems may actually want to bring samples along for help in treating the issues.

Virus wise the best thing to do is to practice hygiene of your tools, but they can and are spread by pests too so that isn’t fool proof.

At the end of the day consider the immense volume of cargo that comes in from all over the world to ports around Australia and you may see why there wasn’t a resounding excitement in the thread, though I applaud your time and effort to put it all together because really I don’t want fire ants in my back garden because old mate picked it up on holiday or something.

Really though the efforts we may make in the Australian bonsai world to help, while well intentioned and may save yourself a few minor pest headaches, in the grand scheme of biosecurity is like trying to cut down a tree with a feather

[greg27]

I feel like there are a two related but distinct points here. One is about ensuring that the trees that we're responsible for are pest- and disease-free so as to not potentially spread those pests or diseases to the trees of our bonsai colleagues, or to sell infected material to the public. I think this is one that everyone can get behind and won't cause much debate.

The other is to do with state or federal quarantine restrictions which is where opinions are going to differ. Life will always find a way but personally I don't think that means we just abandon any attempt at stopping diseases. The COVID example was mentioned - sure, the disease spread across the world despite containment efforts, but you cannot seriously say that those efforts (masks, lockdowns, physical distancing, etc) didn't help to slow the spread to allow more time for vaccine development and for federal politicians to continue doing sweet f all (sorry getting off-topic), or to stop everyone getting sick in a small timespan and completely overwhelming the (horribly underfunded and unprepared... sorry off-topic again) public health facilities and systems.

On the topic of COVID, I'm sure we all saw the news reports of all the millionaires getting a pass out of the country during lockdown to go pick up a luxury yacht or whatever - let's try to not think about all the lovely exotic houseplants they're probably bringing in on those.

So maybe let's separate the discussions. Have whatever thoughts and opinions you like about quarantine, import restrictions, etc. But if you're bringing a tree to a workshop, try to make sure it isn't covered in some horrible thing that might end up killing the tree of the person working next to you.

[Phil Rabl]

I'm disappointed, but not surprised, by the negativity. So, as others have said, can we please concentrate of what good bonsai practice looks like and leave commentary on government policy to newspaper and other blogs.

[Rory]

I'm disappointed, but not surprised, by the negativity. So, as others have said, can we please concentrate of what good bonsai practice looks like and leave commentary on government policy to newspaper and other blogs.

No offence, but this is hypocritical. This post was made in response to Treeman pointing out the often ridiculous procedures of quarantine and biosecurity. But to then request to only restrict commenting on 'club practises', to be somewhat insulting.

Your actual thread is stated:

"Biosecurity and plant hygiene."

Its a public forum.

[treeman]

From a club perspective, getting basic hygiene practices down on paper is a important. As president of the SA Bonsai Society I can tell you we've had many instances of people bringing in trees with obvious signs of pathogens which we have asked them to remove. We have a duty of care for all our members trees and because we have it stated in our constitution we can point this out to people if they arc up about it, and it does happen. For our annual show, trees for sale are inspected. We can't catch everything but trees with scale, signs of virus infection or redback spiders under the pot lids are handed back before they are sold to the public.
Matt.

Matt,
As someone who has grown all kinds of plants for about 40 years now, I can tell you that viruses are rare in the extreme. I have only had one instance in all that time. They are spread through cutting tools mainly. But as said, they are so rare as to be just about a non-issue. As for other pests and diseases, If you have one tree infected by something or other (as sometimes occurs) I can honestly say that I have never once noticed the problem suddenly show up on another tree by it spreading. If one tree is infested with scale or root mealy bug for example, there is always a reason and that is not because it has ''spread'' from another one but because it has been weakened in some way. Usually it's in the wrong position or something similar like root bound or starving or dying of thirst. Root rots effect individual trees and do not ''infect'' other trees. Thrips and white fly and aphids are seasonal and come in waves. They affect all vulnerable trees at the same time. If I found a tree that I wanted to buy due it's rarity and it was infected or infested with anything other than obvious virus (which cannot be cured) I would not hesitate to buy it.
So, although I understand your position regarding club sales, the fear about these things is way over-stated.

[Stevie_B]

I have been told by my daughters how ignorant I am, but I have to say I can't see what the problem with bio-security is.

The border force quarantine regs would surely stop any invasive plants coming in, surely? I guess anyone who buys seeds on ebay is just asking for trouble, but i would doubt that many would actually become viable plants enough to cause concern.

I have a mate in bio-security and he tells me of stories of nurseries being sent seeds from overseas 'companies' for free, asking them to plant them etc. Now that is concerning and i can get behind enforcement for that.

However, I don't know of any bonsai specific problems arising in the bio-security world. If there are any concerns or evidence to support the protocols suggested on this post, then I think they should be tabled for us all to see.

[legoman_iac]

I'll jump on the fence ... firstly, would like to thank Phil for the thread. While generic, and long, felt it a worthwhile read. This is not something I've dealt with much, as I'm mainly a long time reader, not frequent club member.

Ofcourse, having a resource with how to treat the thing I have, or for trees I have, would make life easier (I use this forum as my go to before google). Will have to cross the pest bridge when, hopefully not for a while, I get to it.

I was at a meet up recently, when a new bonsai enthusiast brought in their beloved tree only to be told, "it's infested, we aren't going to touch it today. It's not healthy enough" ... my initial reaction was "ewww, get it out of here" ... then realised, it could have been me, and I really felt for the member. They obviously loved their tree but not educated on what to look for. There's so much to learn to this wonderful art form, and the horticultural side is always "as it's needed" (for me at least).

I have had a Red back on one of my bonsai once ... I removed it as my daughters often help and I didn't like the idea of the two crossing paths, nor me crossing it's path/web. It could have helped keep other pests at bay, but I made a choice.

Bonsai hygienie ... can we agree it's like personal hygiene, let's just wash hands and do the polite thing. Can't imagine anyone deliberately bringing a sick tree to a public place, unless to seek help. However I still get shocked when I see people, especially staff at restaurants, who don't wash their hands after using the restrooms.

If there's a general consensus on what the etiquette is, that's a great start! Having outlines in constitutions is always fantastic, then if you don't agree, don't attend, no?