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Thread: Are you really doing that?

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  1. #1
    Real Name
    Ray Barkalow
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    Default Are you really doing that?

    As a “frequent forumer”, I’ve seen a lot of cases of misapplied “cures”, and get a lot of emails too, so I though I’d share this article from my website:

    The title question - are you really doing that? - can be taken in two ways. The first, stressing the “really”, is an accusation or at least a questioning of your sanity or intelligence. While that may be appropriate in some situations (
    and I'm not leaving me out of that!), in this case, the question is intended to make one question if “what they are doing” really has the outcome they are expecting. In the world of orchid growing, evaluating our actions can lead to a great many examples where the answer is a pretty firm “no”.


    A great example is disinfecting ex-flask seedlings before potting them up. Why? In-vitro culture is inherently sterile, so application of a fungicide or disinfectant treats nothing, imparts no “immunity” going forward and may negatively affect the plants. If you want to give those seedlings every opportunity, consider the application of a good probiotic like Quantum-Total instead, which can reduce or prevent future infections by pathogens.

    Another example is misting orchid leaves to boost the humidity. Humidity, by definition, is “water vapor in the air”, not “wet leaves”. Water on leaves does not evaporate readily, orchids are poor at foliar absorption of water, and pockets of water sitting on the plant make great little incubators for bacteria and fungi.

    A third is the use of the wrong pesticide. There is no use applying an insecticide to a mite infestation, using a fungicide to treat a bacterial infection, and a disinfectant is of no value when dealing with insects or mites. Match the weapon to the prey.

    Those are examples of actions that are more a waste of time and maybe money than anything else, but there is a common one that is potentially quite harmful – incomplete pesticide treatments. It is common for folks who have identified a pest to treat their plants once and assume they’ve gotten them all, especially when using systemic or translaminar pesticides. Unfortunately, that’s not the case at all.

    First, we must recognize that pest infestations likely involve eggs, larvae and adults, and that most pesticides only kill adults of the targeted species. When we treat a plant, it is also likely that our pesticide won’t kill 100% of the adults, allowing the survivors to reproduce and carry on the infestation, adding to the other eggs and immature “critters” that were not affected. Considering the rapid reproduction and maturation rates of most pests, it is usually a good idea to perform complete treatments a total of three times at one-week intervals, greatly increasing the odds of eradicating the entire infestation.

    So, the conclusion/recommendation is that we had better take a moment to evaluate the true cause of any issue, and the impact of our proposed actions, before actually doing something, rather than just “throwing something at the problem”, or relying on “collective knowledge” (“myths” or “old wives’ tales”) at face value.

  2. #2
    Real Name
    Bruce Brown
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    Quote Originally Posted by raybark View Post
    As a “frequent forumer”, I’ve seen a lot of cases of misapplied “cures”, and get a lot of emails too, so I though I’d share this article from my website:

    The title question - are you really doing that? - can be taken in two ways. The first, stressing the “really”, is an accusation or at least a questioning of your sanity or intelligence. While that may be appropriate in some situations (
    and I'm not leaving me out of that!), in this case, the question is intended to make one question if “what they are doing” really has the outcome they are expecting. In the world of orchid growing, evaluating our actions can lead to a great many examples where the answer is a pretty firm “no”.


    A great example is disinfecting ex-flask seedlings before potting them up. Why? In-vitro culture is inherently sterile, so application of a fungicide or disinfectant treats nothing, imparts no “immunity” going forward and may negatively affect the plants. If you want to give those seedlings every opportunity, consider the application of a good probiotic like Quantum-Total instead, which can reduce or prevent future infections by pathogens.

    Another example is misting orchid leaves to boost the humidity. Humidity, by definition, is “water vapor in the air”, not “wet leaves”. Water on leaves does not evaporate readily, orchids are poor at foliar absorption of water, and pockets of water sitting on the plant make great little incubators for bacteria and fungi.

    A third is the use of the wrong pesticide. There is no use applying an insecticide to a mite infestation, using a fungicide to treat a bacterial infection, and a disinfectant is of no value when dealing with insects or mites. Match the weapon to the prey.

    Those are examples of actions that are more a waste of time and maybe money than anything else, but there is a common one that is potentially quite harmful – incomplete pesticide treatments. It is common for folks who have identified a pest to treat their plants once and assume they’ve gotten them all, especially when using systemic or translaminar pesticides. Unfortunately, that’s not the case at all.

    First, we must recognize that pest infestations likely involve eggs, larvae and adults, and that most pesticides only kill adults of the targeted species. When we treat a plant, it is also likely that our pesticide won’t kill 100% of the adults, allowing the survivors to reproduce and carry on the infestation, adding to the other eggs and immature “critters” that were not affected. Considering the rapid reproduction and maturation rates of most pests, it is usually a good idea to perform complete treatments a total of three times at one-week intervals, greatly increasing the odds of eradicating the entire infestation.

    So, the conclusion/recommendation is that we had better take a moment to evaluate the true cause of any issue, and the impact of our proposed actions, before actually doing something, rather than just “throwing something at the problem”, or relying on “collective knowledge” (“myths” or “old wives’ tales”) at face value.
    This is great, Ray. Thank you. The misting orchids issue is still a bit confusing because as a greenhouse grower when I fill the air with water vapor, it increases humidity - it also gets the leaves and roots wet but it helps cool down the air in the summer and, I thought it was raising the humidity. After further thought, I think the raised humidity was due to the gravel on the floor of the greenhouse holding water (maybe?).

    cheers,
    BD

  3. #3
    Real Name
    Ray Barkalow
    My Grow Area
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    Default

    Bruce,

    Here a little scientific/mathematical thing I did to explain my dislike of “humidity trays” and misting:

    Let’s say we have a 10′ x 10′ x 10′ “room” (size selected for calculation purposes). At 74°F (also selected for math simplicity), that volume of air can hold one-half pound of water to give 50% RH. One-half pound of water is about a cup in volume. If the room was totally sealed off, it would be easy to keep the humidity up. Unfortunately, that room isn’t totally sealed from the environment, as there are other rooms in our houses, no house is perfectly sealed, and our walls do “breathe” by design. That more-or-less infinite air mass around us and the laws of nature try to spread that cup of water uniformly over the universe, so we have to replenish the supply to keep up.

    Replenishing the volume or mass of water in the air is dependent upon evaporation rate, which in turn is dependent upon the air and water temperatures, the current humidity level and the surface area of the water source. Look at it this (very simplistic) way: individual water molecules are energetic and naturally move around and “vibrate”. As they do, they collide with other molecules, so their motion is blocked and they “hand off” some of their energy, while getting more from molecules that run into them. The density of the molecules in the air is lower than in the liquid, so at the surface, where there are fewer other molecules to run into, some of those water molecules will have enough energy to “break away” from the liquid and enter the air – as humidity. Unfortunately, that process is not exceptionally fast – place a cup of water on the counter and see how long it takes to totally evaporate. Also, as a water molecule “escapes” into the air, it takes its allotment of energy with it, reducing what’s in the water, thereby cooling it and reducing the future evaporation rate.

    If we heat the water, we give those molecules more energy, so the escape (or evaporation) rate increases. Hence the “warm air” humidifier. Our only other practical alternative to heating is increasing the surface area.

    As this was composed, there was a cup of water on the desk. Its surface area was only about seven square inches, so we wouldn’t expect much evaporation. If we pour that water in a standard nursery tray, we increase that surface area (where the molecules might jump out of the liquid) by almost 35 times to about 250 square inches. That seems like a great increase, but is it a significant one? Unfortunately, no. A tray of standing water still takes a long time to evaporate. The common practice of adding pebbles to the tray so they are kept wet by capillary action may increase the surface area by two- to three more times, but it’s still relatively meaningless. So, to get a substantial surface area, let’s atomize that cup of water.

    Our cup of water is about 237 ml, or 237 cubic centimeters in volume. If we atomize that to 1 mm diameter spherical droplets (much larger than what atomizing humidifiers do in reality), we create over 4.5 billion droplets, having a surface area of almost 22 million square inches! Yeah…that ought to evaporate more quickly than a tray.

    Hand misting may be better than putting water in a tray, but the volume has to be substantial, so would have to be done very frequently – doing so in the morning before going to work has only transient and relatively meaningless benefit. A room humidifier can put several gallons of water into the air in a day, so you can see that a few pumps from a hand-held quart mister really won’t do much. It is also important that it be done into the air, not onto the plants, as all that does is wet the leaves, making a film with less surface area, and it improves the growing conditions for bacteria, molds, and fungi.

  4. #4
    Real Name
    Bruce Brown
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    Quote Originally Posted by raybark View Post
    Bruce,

    Here a little scientific/mathematical thing I did to explain my dislike of “humidity trays” and misting:

    Let’s say we have a 10′ x 10′ x 10′ “room” (size selected for calculation purposes). At 74°F (also selected for math simplicity), that volume of air can hold one-half pound of water to give 50% RH. One-half pound of water is about a cup in volume. If the room was totally sealed off, it would be easy to keep the humidity up. Unfortunately, that room isn’t totally sealed from the environment, as there are other rooms in our houses, no house is perfectly sealed, and our walls do “breathe” by design. That more-or-less infinite air mass around us and the laws of nature try to spread that cup of water uniformly over the universe, so we have to replenish the supply to keep up.

    Replenishing the volume or mass of water in the air is dependent upon evaporation rate, which in turn is dependent upon the air and water temperatures, the current humidity level and the surface area of the water source. Look at it this (very simplistic) way: individual water molecules are energetic and naturally move around and “vibrate”. As they do, they collide with other molecules, so their motion is blocked and they “hand off” some of their energy, while getting more from molecules that run into them. The density of the molecules in the air is lower than in the liquid, so at the surface, where there are fewer other molecules to run into, some of those water molecules will have enough energy to “break away” from the liquid and enter the air – as humidity. Unfortunately, that process is not exceptionally fast – place a cup of water on the counter and see how long it takes to totally evaporate. Also, as a water molecule “escapes” into the air, it takes its allotment of energy with it, reducing what’s in the water, thereby cooling it and reducing the future evaporation rate.

    If we heat the water, we give those molecules more energy, so the escape (or evaporation) rate increases. Hence the “warm air” humidifier. Our only other practical alternative to heating is increasing the surface area.

    As this was composed, there was a cup of water on the desk. Its surface area was only about seven square inches, so we wouldn’t expect much evaporation. If we pour that water in a standard nursery tray, we increase that surface area (where the molecules might jump out of the liquid) by almost 35 times to about 250 square inches. That seems like a great increase, but is it a significant one? Unfortunately, no. A tray of standing water still takes a long time to evaporate. The common practice of adding pebbles to the tray so they are kept wet by capillary action may increase the surface area by two- to three more times, but it’s still relatively meaningless. So, to get a substantial surface area, let’s atomize that cup of water.

    Our cup of water is about 237 ml, or 237 cubic centimeters in volume. If we atomize that to 1 mm diameter spherical droplets (much larger than what atomizing humidifiers do in reality), we create over 4.5 billion droplets, having a surface area of almost 22 million square inches! Yeah…that ought to evaporate more quickly than a tray.

    Hand misting may be better than putting water in a tray, but the volume has to be substantial, so would have to be done very frequently – doing so in the morning before going to work has only transient and relatively meaningless benefit. A room humidifier can put several gallons of water into the air in a day, so you can see that a few pumps from a hand-held quart mister really won’t do much. It is also important that it be done into the air, not onto the plants, as all that does is wet the leaves, making a film with less surface area, and it improves the growing conditions for bacteria, molds, and fungi.
    Very cool, Ray. Thank you!
    Cheers,
    BD

  5. #5
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    Lutz Haunert
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    Wow Ray, thanks for this impressive article. When I read that, I think yes, of course. And actually I knew it. But could I have said it like that? No, I don't always make myself aware of it. Especially not when I'm panicking about an epidemic. Brilliantly succinct, you get to the heart of the matter. I should read it once a month. Like a mantra. I also like the humorous undertone that reminds the orchid lover of his own shortcomings. Thank you very much for this very helpful article.

    ---------- Post Merged at 03:16 PM ----------

    On this occasion, we should not overlook the fact that Bruce really does post by far the wettest orchid photos in the world.

  6. #6
    Real Name
    Ray Barkalow
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    Default

    I also like the humorous undertone that reminds the orchid lover of his shortcomings.

    When I give lectures to orchid societies, I usually start with a reminder: “Societies bring in speakers because they are considered to be experts in the field. Don’t forget that one is not an “orchid expert” until he has killed his weight in plants.” I then pat my stomach and say “…and I apparently am getting room for more “expertise” every year!”

  7. #7
    Real Name
    Bruce Brown
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    Quote Originally Posted by LuHa View Post
    .....On this occasion, we should not overlook the fact that Bruce really does post by far the wettest orchid photos in the world.
    HAHAHA... I always take photos while I am watering in the greenhouse.

    Cheers,
    BD

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