Hello everyone!
I know this will be incredibly long-winded, but I think this is a vital subject for all orchid growers and worth the diatribe.
I really cannot stress the need for excellent hygiene when dealing with your orchids. Due to a variety of causative factors (need of humid, fungus-inducing environment, plants with exposed root and growth tissues which are somewhat easy to abrade or brake, more chemical resistant diseases, etc.), if you want to keep a 'clean collection' you have to follow some basic hygiene rules.
As I am old enough to remember when there was only one species of orchid alive on the face of the earth, (a little purple one, as I recollect
), there was no testing available when I first became interested in orchids - that was decades off. I am a long time smoker and orchid collector, a bad combination. I have lost two complete collections in my early days - well over 600 plants - all to Tobacco Mosaic Virus and subsequent opportunistic diseases.
Pathogens
Various fungal & bacterial infections kill many orchids; this is due to a variety of factors, but most fungus can be controlled by increased air circulation, better watering practices and various natural approaches. Bacterial infections can be tougher to get rid of but there are some effective curatives out there. Cinnamon is effective in preventing some infections. The board will help with identification and treatment if you believe you have a fungal or bacterial infection. But both of these can be spread with infected tools or potting medium, dirty hands and unclean pots. Good hygiene will decrease any cross contamination and will aid in a healthier collection.
As far as viral pathogens go, these are rarely, if ever cured and among these, the aforementioned
Tobacco Mosaic Virus (TMV) is one of the most persistent problems that plague the private collector and orchid industry. This disease is HIGHLY INFECTIOUS, extremely tolerant of disinfectants, incurable and can spread in a variety of ways. Because of these factors, I will focus on TMV; if you can protect against TMV, you can probably protect against most any pathogen. Also, TMV infects and is deadly to a variety of plants, such as begonias, tomatoes, and many other ornamental and garden plants. I will leave it to you to look up the signs of TMV infection, but not all infected plants show signs. Viral infections are not always identifiable by sight, and when they are the plant is usually too far gone to save. My focus is to prevent rather than try to cure or destroy.
How to avoid transmission of any infectious pathogen
Any abrasion in the surface of the plant provides an opening for pathogens to enter a plant. This includes scratches, abrasions, severe light or chemical burns/damage, insect bites/damage, basically any cracks or breaks in leaf, stem or root. When you re-pot a plant, you may want to make sure you have watered it well before removing it from the pot. This allows the roots to become more flexible and less likely to break. When I do have a crack or a break in the surface, I dust it with with cinnamon. It definitely stops the crack from darkening and spreading; it also seems to stop fungus well. It does nothing for TMV or most likely other viruses like Cymbidium Ring Virus, but does seem to stop bacterial / fungal infections.
Just like fungal and bacterial infections viruses can be transmitted to plants, tools, work surfaces, pots, etc by any contact with an infected hand, another plant, a dirty tool, bad potting medium, unclean water, etc. You can pick this virus up by simple skin contact. It exists on surfaces for quite sometime. Ever touch a doorknob after a smoker, anyone?
Now granted, the tobacco product that is handled has to be infected with TMV, but go online and look at the estimated infection rate among tobacco growers.
Some plant dealers have the disease without their knowledge and pass it along, but any commercial dealer should be aware of the signs and ready to react properly if any pathogen is found in their collection.
Keep bugs and pests in check - these are suspected carriers of various viruses and diseases. Plus they just suck the life (literally) out of a collection.
Disinfecting
I have looked into how to get rid of the TMV virus and the only way I have found to protect my collection is personal diligence with good hygiene.
This means washing my hand thoroughly with soap, not smoking around my plants, using hand sanitizer, wearing nitrile gloves if needed, sterilizing all tools, medium, pots, - PROPERLY CLEANING ANYTHING THAT COMES IN CONTACT WITH YOUR PLANTS.
Anything you can heat up you can sterilize. I microwave my damp ceramic pots (non-glazed) and damp potting medium. Steaming surfaces will work also, but you have to really heat up the surface as it takes high temps to kill TMV.
Various chemicals are available to protect plants and disinfect surfaces - you have to wrestle with how far into chemical use you will go and that is up to you. Bleach will kill basically all pathogens, but you have to use it properly and carefully. (
When I work, I place black and white newsprint down which is usually extremely sterile thus no need to sterilize the work surface - no chemicals )
Ultraviolet light disinfection is often used to sanitize water but TMV is the hardest virus to kill. With ultraviolet light, the second most difficult virus to kill, infectious hepatitis, takes 8,800 UV units to be killed. TMV requires 440,000 of the same units to kill 99% of the virus. It is Tuff - Stuff!
I know that others are talking about how you can fertilize and use trace elements to strengthen an infected plant, but
the plant is still infected and a threat to every other plant it can transmit to. There has never been a documented case of a plant ridding itself of this virus, nor being cured in any way and I cannot support just making an infected plant better looking.
Seedlings from an infected plant will not be infected, and the basic recommendation for retaining a desired plant is to breed it to itself. If you are able to make it healthy enough and feel you can isolate it from your other plants, nurse it until it is strong enough to bloom, be self-pollinated, form a seed pod to ripen, then you can retain the lineage or species. But I would still destroy the mother plant.
DO NOT MULCH INFECTED PLANTS - you will just infect your mulch.
Testing
If you question an orchid's status, there are various test which test for kits that screen for the most prevalent viruses. They are easy to get and use.
If you have a collection that is worth your concern, then I cannot recommend testing suspect plants enough.
A recent report stated that a high level of phalaenopsis orchids imported from Asia are testing positive for TMV. Not sure how they would get past the required import sanitation requirements, but there are several reports that are floating around online.
Which brings us to the final point -
purchase only healthy looking plants from reliable sellers. I know that I am not the only seasoned collector who has been so taken with a bloom we have bought a sickly to plant. DO NOT DO THIS. In time you will learn to appreciate the health of the plant rather than the blooms it may currently be showing; this is how you build award winning collections. Many of us are good Samaritans to the marked-down plant bin. But there is a difference between a neglected plant that can be revived and a sickly plant; learning the difference will save you money in the long run.
If you do buy sight unseen (off the net for instance) then do not accept plants that have distorted growth, odd foliage coloring, color breaks in blooms, or anything that makes you wonder about the health of the plant. If you have a question, post a pic on the board and see what the experts think. If you are concerned about a plant, isolate it and ask for some assistance.
Why is this so important? Only a healthy collection provides you with the best plants and blooms; this is a deadly disease and should be eradicated. If you can protect your orchids from TMV you can probably count on not having a lot of other pathogens in you collection.
Thanks for letting me rant. I hope you all have wonderful collections that are blessed with health. Currently my collection of 125 plants are all clean and free of disease (to my knowledge). Just be diligent and make sure you are working with clean plants, clean tools and clean hands! Take it from a dinosaur - good hygiene pays off!
Steve
Need for hygiene with orchids
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