Orchid Pest and Pathogen FAQs

      Created by: Aaron J. Hicks, for the Orchid FAQs series

      No responsibility taken for the advice within. Always read
labels. Always follow the manufacturer's advice. When in doubt, ask.
Don't do anything your mother wouldn't do. Don't sue me, I'm broke.
And hey hey HEY HEY!    Let's be _careful_ out there.

      Orchids are quite possibly the most diverse plant family on Earth;
they grow under a variety of conditions, and are known from all
continents but Antarctica.
      For all intents and purposes, most orchid growers will be
restricted to cultivating the tropical epiphytic species, and the
terrestrial species (known more properly as littoral species, as
few orchids actually grow in dirt). As a result, these pest and
pathogen guidelines will apply primarily to these species and hybrids-
tropical species.
      Speaking very generally, these principles will apply to the
majority of tropical plants, although orchids can be more susceptible
to certain viruses and other pathogens than other epiphytes, such as
bromeliads and epiphytic ferns. The same is true of pests; there is
little difference in routing out a scale infestation found in, say, a
Boston Fern, than in your favorite Phalaenopsis.

      The first general rule is that one should not violate the labeling
on any pesticide, fungicide or any other agent that is applied to plants.
In order to be labeled for a certain application, pesticides must undergo
rigorous testing for that application. As these testing procedures are
expensive, few companies find it profitable to receive labeling for their
product on orchids. Further, many of those agents certified for use
on orchids are NOT certified for use in the home, and are thus unsuitable
for application on orchids raised either as houseplants, or in greenhouses
attached to a living area (lean-to greenhouses and the like).
      Most pesticides are chemically related to nerve agents; toxicity to
humans will not be noticed until concentrations are very, very close to
lethal levels. As a result, by the time someone displays symptoms of
toxicity, it is a very grave situation indeed.
      Many pesticides are damaging to a plant when applied at a
concentration stronger than what the label specifies; similarly, if it
is applied at a rate lower than what is suggested by the label, it
may not kill as effectively as desired (which also has the nasty side-
effect of inducing resistant strains of insects to form). Any pesticide,
regardless of strength or labeling, may potentially injure any plant
it is applied to; conditions such as temperature, light, water chemistry
and other non-specific items can cause pesticides to act adversely
or incorrectly. Even the time of day of application can cause damage;
consult other local growers as to when they apply pesticides, according
to your local conditions.
      It is worth a few moments to describe pesticide resistance.
      A number of strains of insects have developed that have a
resistance to certain pesticides, or even entire groups of pesticides.
Improper application, or repeated application, may cause pests to become
"immune" to such pesticides; insects are able to adapt and evolve quite
rapidly, given their numbers and the number of applications per year
of a given pesticide. Improper application (as has been described above)
is a major contributor to the problem; if we spray 10,000 insects with a
pesticide at 50% of what the label describes, or it is somehow diluted
by ambient water on the leaves, etc., we would expect more insects to
survive than if we applied at normal (100%) strength. Those few insects
survive, reproduce, and are exposed again; this time, more insects survive
than the last time, given an adaptation to the applied chemicals. This has
been shown to take place with chemical as well as biological controls
(BT, or Bacillus thurengiensis, as applied for caterpillars on ornamentals).
      Follow labels and all accompanying instructions to the letter. If there
are any questions about handling such materials, be certain to contact
the manufacturer and get clarification. Always use gloves, respirators and
other protective gear that is compatable with the materials being
applied. It is important to note the pathways through which a pesticide
or other agent will prove to be harmful.


      Pathways are Oral, Skin, Inhalation and Injection.

      Oral pathways involve ingestion, either direct or indirect, of a toxic
material. This is to say, the material must be swallowed. Indirect exposure
may occur through ingestion of contaminated material; for example, if
one were to eat a sandwich after contaminated hands had touched it,
indirect exposure could result.
      Skin pathways involve absorption through the skin. Many highly
toxic materials can be absorbed through the skin, often with rapidly
fatal results. As with oral pathways, exposure can be direct or indirect.
Handling a pair of contaminated gloves can result in exposure to a chemical
nasty that will be as hazardous as direct spray exposure.
      Inhalation is exposure to a compound through the lungs.
Contamination may result from exposure to gas, aerosolized liquids, or
suspended solids. Injury or death may result from the toxic chemical
properties, or asphyxiation if enough oxygen as been displaced.  Many
of the chemicals that are extremely dangerous from the inhalation route
have some unusual properties, such as desensitization or toxic levels
being close to that of detection. Desensitization involves an effect where,
after the first smell of a gas (which may be just a tiny whiff), no more is
detected. As a result, the person fails to perceive any more gas after it
is initially detected. The second involves very toxic chemicals where
the first indication that any gas is present indicates that concentrations
are already high enough to kill a human (cyanide, for example, smells
of bitter almonds. That one can smell this means that levels are already
at levels high enough to kill, given time). Further, many toxic gases
have no odor, no color, and will kill with no warning.
      Injection involves failure of the skin as a protective barrier. This
can occur through any penetrating injury. For our purposes, this is of
relatively little concern, provided that any application of product takes
place such that anybody who is potentially exposed has no open wounds,
and takes precautions not to receive any such injuries when applying
materials (no exposed cutting tools, no exposed wires in the greenhouse,
etc).

      All of this material may seem superfluous, even overly paranoid.
Speaking as a grower of 13 years, I know of several incidents of pesticide
exposure by small growers which have led to hospital stays due to
mis-application, improper procedure, or simple stupidity or ignorance of
the products being applied. I can also speak of a commercial grower who
lost an eye as the result of an injury sustained in the greenhouse
involving an exposed wire. I like my hobbies, I like my greenhousing,
I enjoy my plants- but none of it is worth a hospital stay or the
loss of an eye. As improbable as any of it may sound, people do get hurt.
Those that do often become very strong advocates of techniques and
materials that involve less risk. I will attempt to pass along as many
of these techniques as possible.


      1) Pests

      Orchid pests come in many forms. The most common are insects,
which are generally broken down into two types: suckers (like scale
and aphids), and chewers (like slugs). Most pests are more readily
prevented than cured. Prevention consists of several steps. The best
prevention involves general plant hygiene; keep the plants clean. Keep
the leaves free of dust (this is a big one in the home; dirty leaves are
breeding grounds for scale and mealybug)- give your plants a shower,
mop their leaves with a damp sponge or a paper towel. With Cattleya-
types, remove old sheath paper when it has died and dried out; scale and
mealy like to hide in the space between the dead sheath paper and
the pseudobulbs. Pick up dead flowers that have fallen off plants, leaves
that are lying on the benches, and other hiding places for slugs and
earwigs.
      The second is to look at your plants regularly. Infestations,
for some peculiar reason, tend to "hide" from the grower. Many
insects cling to the underside of leaves, or on the far side (the one
next to the window, the one you never check unless you pick the
plant up and check it out). When you water your plant, check for
detritus that washes out- particles that are of similar shape and
size may be fecal pelets from "residents" instead of simple breakdown
products, indicating (pardon the pun) a deep-rooted problem. Look
for slime trails on the leaves and benches when you get up in the
morning; slugs may not appear topside, except at night, while they
erode away the root system from below. Look for chewed green root
tips.
      One last suggestion is to inspect plants when brought in from
lengthy stays outdoors; plants tend to accumulate pillbugs, earthworms
and other pests if they have been maintained outdoors for the summer.
More often than not, the pests they pick up are not plant "nasties",
but live in the detritus that results as organic media breaks down.
Many of these will occasionally nibble on soft, live roots, or chew on
a tasty flower (as a rule, it will always be a flower you were going to
take to show). Inspect plants carefully before bringing them inside.
Look for chewers or signs of media breakdown. More importantly,
try to prevent pests from infesting your plants; keep them up off
the ground while they are outside, keep them away from your composted
materials (slug breeding grounds), and so forth.
      None of this is to say that plants should not be kept outside; to
the contrary, the author has discovered that the best treatment for
seriously entrenched infestations is to put the plants outside when
temperatures are appropriate. The wind, rain and temperature swings
will help clear infestations that pesticides, hand-picking and other
treatments will not be able to do. For instance, one large Platycerium
(Staghorn Fern) I had would get the nastiest chronic scale infestations
I have ever seen. In the summer, it would clear up completely after
only a couple of weeks outside (being a well-established plant, it would
even take temperatures lower than 40 degrees Fahrenheit from time to
time with no harm).

      A) Aphids
      Aphids are small, winged sucking insects that seem to come from
nowhere; they can be almost any color, and are about 1-3 mm long.
It has been said that aphids are born pregnant, and anybody who
 has had a bad infestation will agree. Aphids often crop up during hot,
dry weater, and can be difficult to eradicate. With many plants, aphids
often appear only on soft, immature growths, especially flowering spikes
or the flowers themselves.
      Many sprays can be used on aphids; use as labeled. Several insect
predators are available, such as ladybug larvae.
      A yellow bowl, filled with water and a bit of dishwashing detergent,
will attract aphids (they like yellow); infestations can be reduced through
use of such bowls. Laminated yellow cards can be smeared with
Vaseline or similar products, which results in adhesed aphids, which
can also reduce numbers. Wipe clean, re-apply Vaseline, and place
next to affected plants. Some people use yellow party cups which have
been treated in a similar manner.
      If the infestation is small, the most thorough manner to eradicate
an infestation is as follows:
      Sterilize a bucket that is large enough to contain the entire plant;
a 5-gallon bucket works well for most house plants. Sterilize with 10% bleach
solution for at least an hour.
      Put the plant in the bucket, and add a tiny drop of dishwashing
detergent in the bottom. Fill the bucket slowly with water; remove any
pieces of media as they start to float away (most will be retained in place
if there is a decent root system; otherwise, it may be held in place with
gauze or cheesecloth). Fill the bucket to the point where the entire plant
is submerged; the aphids will drown, or be washed away as the bucket
is allowed to overflow. Treat early in the morning, so that plants will
be thoroughly dry by evening, to prevent rotting of "soft" plants (such
as Phals). Repeat as necessary.
      This technique also works well for aquatic plants, which are often
plagued by aphids during hot, dry summers; floating plants may be
weighted down with rocks in a cloth or burlap sack for 24 hours or so.
Water lillies may be moved to deeper water, or the leaves may be bundled
together, and weighted down as a bunch. Ever since newspapers switched to
soy-based oils, it has been safe to throw newspapers over the affected
leaves. Capillary action draws water up over the newspapers, and smothers
many of the insects. This reduces numbers, but not as well as complete
submersion, and it's also messy to clean up the shredded newspapers.

      B) Scale
      There are several types of scale. The two broadest groups are brown,
hard scale and white, papery scale known as biosduvial scale. Both
types adhere to the leaf surfaces, and are easily removed with a
fingernail. They range from less than 1 mm across to 4 or 5 mm in
diameter.
      There are several chemical pesticides available; apply as labeled.
Spreader-sticker agents added to the spray mix may be of value, as
most scale have a waxy covering that tend to shed liquids that have
been applied, making them less susceptible to pesticides without a
spreader-sticker agent. One relatively new product is an inert oil,
which suffocates the scale, known as Sunspray. It is a simple
petroleum distillate, which (in theory) possesses very low toxicity;
it has proven to be quite effective on scale.
      Scale and mealybug are commonly found on the underside of leaves,
and also on the spikes and flowers. They also excrete a kind of honeydew,
that appears on leaves or benches directly underneath infested leaves,
which is often one of the first indications of a problem. It is sticky, and
makes affected leaves shiny with "gunk".
      For the home grower, scale are best removed through removal with
a Q-tip soaked in isopropyl or rubbing alcohol. Although the scale is
removed very easily, it can leave behind eggs; the alcohol helps remove
or kill any eggs that might remain. Larger infestations can be treated
using a toothbrush instead of a Q-tip. Be certain to get ALL the nooks
and crannies; scale is very persistent, especially the thin, paper-white
biosduvial scale.
      Scale, and its cousin mealybug (see C, below), do not like water.
Thus, showering the plants (cleaning them in the tub with a lot of
water after a alcohol application), washing the leaf surfaces, the
pseudobulbs, etc., can be of use in routing out bad infestations.
Any treatment regimen will have to be repeated after 7-10 days or
so, when any eggs would have hatched.
      Some growers have recently advocated the spraying of entire
plants with either diluted or undiluted alcohol solutions, or Lysol (which
has high concentrations of alcohol). I have heard several stories of
plants succumbing to odd disorders many MONTHS after such treatments,
but reports are spotty. It is strongly suggested that such wholesale
exposure to alcohol be restricted until such time that these claims are
either substantiated or refuted. Localized application on the leaves of
orchids (the technique above) has no such track record that I am aware of.

      C) Mealybug
      Mealybug resembles tufts of cotton. It is very similar to scale, in
both treatment and its properties (it is, after all, a relative). Most
pesticides
certified for use on scale can also be applied for mealybug. As with scale,
spreader-sticker agents may need to be applied.
      Mealybug have a great aversion to water. The "tub scrub" for scale
also work with mealybug. Otherwise, treatment is very similar to that of
scale. As with scale, be thorough- eggs (which are not detectable without
magnification) and smaller bugs can hide in the folds of pseudobulbs.
      Neither scale nor mealybugs appear to be very mobile, but they do
move. They will commonly infest adjacent plants.

      D) Slugs
      Slugs are snails without shells. They generally feed upon dead and
decaying matter, but sometimes decide new roots are irresistable. Sometimes
they choose to munch upon flowers.
      Slugs like moisture; keeping the space under benches and between
plants from remaining wet is important in keeping massive slug
populations from building up. Keeping rough, slug-hostile material on
greenhouse floors is important to keeping slugs irritated; this means
coarse brick, sharp lava rock, coarse gravel or sharp sand, none of which
appeals to slugs very much. Growing plants under the benches (Wandering
Jew, ferns and the like) is a virtual welcome mat to slugs, and encourages
breeding of the nasties.
      Slugs like beer, and laying out tins of it, flush with the ground, will
often result in a slug slaughter of mass proportions- they crawl in and
die. Many people report problems with this technique- they come out
at night to check their progress, and find the slugs "sipping" beer, without
falling in. This can be remedied by varying such things are the level of the
beer, the material and shape of container, and so forth.
      Many plants may harbor slug populations on a chronic basis;
banana trees are one such plant- they will hide in the stalk, and one
single plant can harbor many hundreds of slugs (which is a gross-fest
of Biblical proportions when you cut one open- personal experience).
      Populations can be controled through a number of other techniques.
For most growers, hand-picking will be the easiest. Slugs tend to come
out at night, usually when conditions are moist and humid. Check your
growing area with a small flashlight, looking for telltale slime trails, and
for the slugs themselves.
      Another trick is to put out half of a head of lettuce, upside down,
on the greenhouse floor. Wet down the lettuce and the area around it, and
then inspect it for slugs regularly. Pick and destroy, or simply dispose of
the lettuce when it is either full or too far along to be of any more use.
      Metaldehyde bait is the most commonly applied chemical for
use in killing slugs. Scatter bait liberally under benches and beween plants.

      E) Earwigs
      Earwigs are small black and red insects with "pincers" on their tail.
They are chewers, and tend to go after softer plant parts, such as flowers
and new growths. They are from 10 to 16 mm long, or so, and are very
thin- they can slip into very tight areas.
      Earwigs are best dealt with through hand-picking. When moving
plants, always check under the pots, where earwigs will sometimes hide.
Also check very tight areas (such as the new growths on Cymbidiums, for
example) on the plants. If you suspect an infestation in the media a plant
is potted in, sterilize a bucket, place the plant inside, and start pouring
water in. Earwigs will crawl up and out of the media, where they can be
removed and destroyed.

      F) Pillbugs
      Pillbugs, also known as sowbugs or armadillo bugs, are arthropods
that are dull grey in appearance, that appear to be "armored" in appearance.
They are small (up to about 12 mm in length), and roll into small balls
when irritated. They are fairly harmless, living on the detritus that results
from the breakdown of media; if you spot large numbers of pillbugs
plaguing a particular plant, one thing to consider is that the media has
broken down, and the plant may require repotting.
      Dealing with sowbugs is similar to dealing with earwigs; hand pick,
and flood them out as required. This is one pest that tends to come in with
plants that have been brought in from staying outside in the summer;
inspect and treat plants carefully when you are ready to bring them in.

      G) Whitefly
      Whitefly are just that- little white flies. They are tiny (2-3 mm in
length), and have wings. They are sucking insects, and probably act as
vectors.
      Whitefly populations may be decimated through cleaning the plants,
although this is difficult; as soon as you pick up the plant to clean it, a
profusion of insects become airborne, and will thus be missed in any further
cleaning attempts. Spraying in place is often the best option.
      Another option is to control them with the yellow card, as described
under Aphids (above).
      Although the author has never tried it, the bucket-dunking technique
probably works pretty well for serious infestations.


      II) Pathogens

      Orchid pathogens, like pests, generally result from plant stress.
Healthy plants growing under proper cultural conditions will tend to
remain pathogen-free.
      The single most important parameter (after temperature and
watering) is air circulation. Larger numbers of plants, along with packing
them more densely, require higher levels of air circulation. The reason is
simple: higher levels of air circulation will prevent water from staying
on the leaf surface; allowing water to remain on leaves will permit fungal
spores to germinate and get a foothold, infecting the plant.

      A) Viruses
      Viruses infect plants much in the same manner as they infect
animals. The primary difference is that, as plants lack an active immune
system, infection in a plant is a systemic and permanent event: once a
plant is infected with a virus, it will always be infected with a virus.
Further, propagation of an infected plant will result in infected siblings
(except meristems, if performed correctly- meristem tissue is, in theory,
uninfected as the tissue grows too fast for the virus to keep up with it.
As a result, propagules will lack any viruses that the parent plant had.
Unfortunately, as soon as they are de-flasked, they are vulnerable to
being infected with plant viruses).
      To make matters worse, it is difficult to tell if a plant is infected
with a virus; typically, viruses will manifest themselves in actively growing
tissue, generally through production of dead (necrotic) black tissue, be it
in bars, streaks, rings or any one of a number of odd or unusual shapes.
They may show up on leaves or flowers. Growths may be stunted, twisted
or show other odd growth affects.
      Even once symptoms show, it is impossible to determine just from
looking at a plant if it is virused; bacterial or fungal disorders, chemical or
sun burns, or any one of a number of other effects may mimic virus affects.
Certain problems (such as "accordion folds" from dehydration in Miltonias)
may resemble virus affects; aphids may twist and stunt young flowers
while in their bud stage, and so forth. For proper determination, plant tissue
must be sent to a lab specializing in orchid virus diagnosis, which will then
be sceened utilizing a standard laboratory test for viruses known as the
ELISA test; it is highly reliable, but rather expensive if one requires
screening of a large number of plants (about $2 or $3 a test per virus).
      Once a plant has been determined to be virused, it must be discarded.
A few commercial growers maintain collections of highly valuable virused
clones; these can be used for seed production as it is generally thought that
the pollinia can still be used for production of un-infected plants (again,
the plant parts grow too fast for the virus to keep up). This is risky for the
average home grower; should insects feed upon such virused plants, they
can transfer the virus to other plants when they move to feed on them.
Such insects are called "vectors", and most any sucking insect can be a
vector, although aphids are particularly noxious vectors, and have been
recognized as being vectors for a number of plant viruses in a number of
different plant families.
      To help prevent transmission of viruses (and other pathogens),
cleanliness is of paramount importance. Pots should be cleaned and sterilized
before repotting (10% bleach solution overnight for plastic, or baking of
clay pots; this has been refuted for Paphiopedilums; see Orchid FAQ,
current edition). Your hands should be clean before, and between, plants
when repotting; latex gloves are useful if a large number of plants must be
repotted; if you so desire, an alcohol hand scrub (or povidone iodine hand
scrub) can be substituted, but is not absolutely necessary. Remember:
infected plants can, and generally do, look "clean".
      Cutting tools must be sterile; going from plant to plant, lopping of
flowers or other live tissue, is how most plants become infected. Many
growers use sterile, single-edge razor blades for this purpose. Otherwise,
blades must be sterilized utilizing heat (no chemical disinfection has proven
to work with absolute reliability; the primary problem is large gobs of plant
tissue (several cell layers, for our purposes), which the chemicals can not
penetrate in order to deactivate the virus. Remember: viruses are very
complex, extremely delicate structures, but chemical exposure for
disinfection must be thorough and complete; no techniques for this are
readily adapted to the home greenhouse.
      For heat disinfection, many growers use a small propane torch,
mounted to the bench in a manner that will keep it upright no matter
what. As many greenhouses use plastic polyethylene sheet as a barrier
material, this is not advised, as this plastic is highly flammable. Even under
other conditions, keeping such a high temperature flame about the
greenhouse is not advisable (kids, not seeing the flame, forgetting to shut
it off, gas leaks, etc.). Thus, an autoclave is more acceptable (a pressure
cooker that can be used for canning or flasking is also suitable). When
viewed from this perspective, disposable razor blades are an appealing
option.
      The author realizes how many growers become attached to their
favorite pair of pruning shears, favorite straight razor for lopping off
flowers, and so forth. Such implements need to be sterilizable; dipping in
alcohol and "flaming" has proven to be unreliable, and still has a substantial
cross-infection rate. Such tools are best kept for use on plants other than
orchids, or all stainless steel versions be purchased, which can then be
autoclaved.
      Many orchid growers will refute the value of such information,
and insist that "their techniques" work just as well as anything requiring
laboratory sterility. It is worth pointing out that we do not know what
problems plant viruses may present; infection of repeated generations
of orchids may present problems that orchid growers of the future may
regret that previous generations have committed them to. Remember:
viral infection is incurable. Some genera of plants are not capable of being
meristemed, leading to permanent infection of the "bloodline". Many of
the rare and unusual genera of plants in cultivation have not been exposed
to the plant viruses found in cultivation today; we have no way of telling
what complications may result from such infection. Keep your plants
clean, and encourage others to take similar steps, as there is no way of
telling if a plant is infected or not. Nobody wishes to purchase an infected
plant; I seriously doubt any honest dealer wishes to knowingly sell
one, either.
      None of this is to say that viruses are necessarily debilitating; some
plants may go infected for years, and show no symptoms. On the other
hand, certain "sensitive" genera (Pleurothallids, for example) are readily
infected, and rapidly fall prey to a variety of plant viruses.
      One further note: tobacco is susceptible to a virus called tobacco
mosaic virus, or TbMV; it was the first virus recognized to infect plants.
A strain of it does infect orchids, called TbMV-O, for orchid. It is strongly
suggested that orchid growers not permit use of tobacco in any form near
their plants (it has even been reported that the virus will survive
combustion, and can be spread through smoke particles). If one wishes
to see true viral paranoia in action, I invite the reader to ask any collegiate
plant geneticist who works with tobacco what his or her constraints are
upon visitation into their research greenhouses (this holds true even of
scientists who work with the "R" strain of tobacco, which is thought to be
resistant to the virus by locally dying at the site of infection to prevent
the entire plant from becoming infected). Would that orchid growers, both
commercial and hobbist, adopt such attitudes towards viruses, they might
not be of such grave concern.
      Along these same lines, nicotine sulphate is derived from tobacco.
It probably harbors the active virus; use on orchids is discouraged.
"Home-brew" insecticides made from tobacco are also strongly discouraged.


      Generalized Pathogens

      1) Root rot
      Root rot is a very paradoxical condition. The plant typically
demonstrates symptoms of dehydration- the leaves will crinkle, the
pseudobulbs will shrivel, and roots will appear dead and decaying
when unpotted.
      So, as the plant looks dehydrated, the logical step is to increase
watering, which perpetuates the condition: increased water causes
the roots to rot, which causes the symptoms of dehydration to get
worse.
      Treatment: if a plant that appears seriously dehydrated does
not respond to increased watering immediately, suspect root loss.
Probe into the media, seeking any roots. If you are unable to find
any live, healthy roots (especially in the growing season), consider
removing the plant completely from the pot. If, in either case, the
media is thick and decaying, overwatering and resulting media
breakdown is most likely the cause of your problem.
      Note well that there is one exception to this situation: if a plant
is massively overgrown, and the media is still healthy in appearance,
it is possible that the plant is grossly underpotted: the plant removes
almost all available water within hours or days of being watered,
mimicking root loss. Increasing humidity, or top-dressing with a
water-retaining media like sphagnum moss, until such time that
the plant can be repotted at the right time of the year may be a
workable solution for this situation.
      To further the situation, decaying media allows for plant
pests to thrive- slugs, earwigs, pillbugs and the like, which may decide
that a root system already weakened by stress from poor aeration may
make an appropriate snack.
      If the media is not significantly decayed, your problem is simple
overwatering. Depending upon the severity, you may or may not have to
take severe steps to allow the plant to recover.
      Plants with pseudobulbs that have lost most of their root systems
are best dealt with by completely unpotting the plant, and removing
all the media. Remove dead roots with a sterile razor blade (in case
the roots aren't dead after all). There are several options as to what to
do next.
      Some people advocate throwing the "stripped" plant under a bench,
in a clean place. After a dry spell of two or three days (or more, if the
plant can take it), mist the plant two or three times a day; with no media,
the roots will be exposed briefly to water, which is then allowed to
evaporate or be absorbed- not long enough to rot them. When new roots
appear, repot in fresh media appropriate to the plant (note: you may
have to underpot the plant with its smaller root system).
      A modification of this technique is to dust the root system with
rooting hormone first; this has been known to work (according to
my sources, but I have never tried this personally).
      Another technique is to mount the plant (to plaque it, either on
cork or similar media). Mount the stripped plant, either with monofilament
fishing line, nylon cord, or other favored cordage. Put it in reduced light,
and mist the plant periodically until new roots appear. Gradually
increase light and water until the plant has recovered.
      A third technique involves simply suspening the plant by a wire,
and misting it on a regular basis, much like the under-the-bench technique.

      If the plant is not so far along, repotting the plant (into a smaller
pot, as appropriate) is a workable technique. Treat the plant with an
appropriate fungicide (Captan, Benlate, etc) as a drench, and continue
on under a reduced watering schedule. Keep in mind that many plants
that are normally kept on plaques in greenhouses can not be maintained
in such a manner in the house. As a result, many people will pot these
plants, with poor results. Most available pots are too deep for such use,
and the media will stay too moist for too long, leading to rot. If such plants
are potted in shallow pans, or pots that are cut down to make them
shorter, they can often be raised in the home without having to mist them
several times a day, as plaquing would otherwise require. By way of
example, many Encyclias can be cultivated in shallow pans.

      "Succulent" orchids, like mule-ear Oncidiums and Trichocentrums,
can be treated in a manner similar to orchids with pseudobulbs when
salvaging them from root loss. Many of these plants adapt well to
plaquing.

      Monopodial orchids, like Phalaenopsis, are much more difficult to
recover from root loss, as they lack the capacity to store as much water
as sympodial orchids do (with their pseudobulbs).
      Many times, such orchids will be beyond salvaging; I have had
success moving them into pure dried sphagnum moss, and watering
very carefully. The under-the-bench technique has also worked for
some, and the addition of rooting hormone may be of value.
      If root growth is "stalled", as it sometimes does with Phals, I
remove the top inch or so of media, and replace it with dried sphagnum
moss; mist this dried moss 2-3 times a week, just enough to wet down the
roots. This will encourage root growth on the surface without wetting the
plant through-and-through, which helps prevent rot.

      2) Rots, blots and infections
      As it has been said before, orchid pathogens are best dealt with
through avoidance- proper air circulation, watering regimens and
other cultural techniques when applied correctly will prevent most
problems. Being from western Pennsylvania, on the other hand, I
can understand how there are certain times of the year where the
humidity is high, the light is low, and the plants simply ROT.
      During these times of the year (March was always hard on my
collection), keep water off the leaves, increase air circulation, and
watch out for how the daylength increases without a corresponding
increase in outdoor foliage (which can abruptly burn plants).
      But, no matter what we do, the occasional plant will get a brown
spot on a leaf, or a Phal will rot from the crown, or a Paph will
decide to go black, and risk an entire compot, or a large potfull of a
treasured clone.
      I'm no plant pathologist, and for the average small grower,
differentiating between the types of rot and the organisms that cause
them are secondary to routing out the problem, and attending to the
cause as quickly as possible. For further information on diagnosis, I
refer the reader to either Mary Tyson Northen's "Home Orchid Growing"
(a fine tome for the novice as much as the established grower), which is
in its 4th edition, and the American Orchid Society's manual on plant
pests and pathogens. It is replete with excellent photography, the latest
advice and many techniques for preventing and clearing problems. It
is in the second edition.
      Many minor problems will imitate rot; light burns (which are
actually thermal burns, caused by the leaf heating up faster than it
can shed that heat) appear very similar, but are dry, and tend to be
black in appearance, but may also be brown.
      No treatment is necessary for light burns, unless they are in an
area where they might collect water (as a sunken spot), and encourage
rot; in this event, cutting a small drainage hole with a sterile razor blade
might be appropriate.

      Sunken spots that appear wet or slimy are typically pathogenic
in nature. They may smell funny, spread rapidly (sometimes very
rapidly), appear in profusion or otherwise appear abnormal.
      When possible, excising affected tissue with a wide "buffer zone"
with a sterile razor blade may be the best course of action; it is left
up to the judgement of the reader to decide what may be enough live
tissue to prevent further infection, but 1/4" to 1/2" or more is
generally plenty.
      If the tissue cannot be excised (such as the left base of a Phal,
or the junction between leaf and pseudobulb of a Cattleya), keep the plant
as dry as possible, and pack the area with powdered cinnamon.
Although I have not tried this technique, many growers swear by
it, having been adapted from cactus and succulent culture. Evidently,
it dries out the area, and may have some antimicrobial affect aside from
this dehydration activity. If the area continues to spread despite such
treatment, sacrificing the area may be necessary.
      Survival of afflicted tissues is variable; I have seen entire Phal
leaves survive for upwards of two years with 90% of the leaf base
destroyed from rot, with negligible affect on general plant health.

      It cannot be stressed enough that proper cultural conditions will
prevent most of these radical treatments (excision, etc). Water left standing
on the leaves will allow fungal spores to germinate; by the time the
spores have established themselves, a considerable volume of tissue
may be involved, and the plant may be lost.
      Such is the case with crown rot. Water is trapped in the crown of
sympodial orchids, and stands long enough for a fungus to establish
itself. By the time it is detected, the rot has already turned the crown to
black or brown mush, and the plant is probably lost. One such plant
(a favorite of the author, who has, paradoxically, never had success with
it) is Phalaenopsis gigantea; this species, which is probably extinct in
the wild, grows to immense size, but is very "soft", and susceptable to
fungal and bacterial infections.
      This is a particular problem with Phalaenopsis and Paphiopedilums,
and allied genera. For the majority of cases, the plants must be disposed
of. On the other hand, if it is a particularly valuable plant, it is not
completely unknown for some plants to sprout offshoots, which then turn
into viable specimens. It should be stressed that this is uncommon, and
all one can do is wait and see.
      There are a number of fungicidal agents that can be used on orchids.
Some (Captan and Benlate) have already been mentioned. Their effect is
primarily as a peventative; the author has personally had no success
in "curing" infections through the use of such agents. It should be
pointed out that, used as a preventative, such agents will eventually
produce a resistance response from targeted organisms; this is to say,
continued use of fungicidal agents will eventually produce fungal strains
that are resistant to these fungicides, in a manner similar to insects
that have gained resistance to insecticides. Prevention is the key, rather
than growing under stressful conditions, and slathering plants with
expensive chemicals, praying they will stay healthy.
      It is worth mentioning at this point that Physan-20 (also sold
under another brand name, RD-20, I believe) has never substantiated its
claim that it is virucidal (capable of killing viruses). It is strongly
suggested
that it not be used in a manner intended to kill viruses on any surface.

      Pathogen Mimicry

      Many conditions or situations mimic pathogens. Here are some very
generalized ones.

      1) Pseudobulb growth
      The first Oncidium I ever owned was a very young specimen, and
had had no pseudobulbs when I purchased it. Some months later, its new
growth split apart, almost as if the entire growth was wilting; it was
very distressing. Turns out a new pseudobulb was wedging its way to
the surface. Perfectly natural, of course, but unexpected!

      2) Leaf crinkle
      Sadly, not all growers can grow all plants under all conditions.
      One orchid company (which, tragically, no longer deals in orchids)
used to send free plants with every order. Being cool-growing seedlings
that they used to send out, they all fared poorly under my warm to
intermediate growing conditions. The leaves would form awful "accordion
folds", which are indicative of overly warm (and sometimes dry) growing
conditions for the cool growers (Miltonias, cool-growing Odontoglossums,
and the like).

      3) False leads
      Cattleya-types will form short stubby nubs at the base of old growths
just before they start growing actively; they are indistinguishable from
"normal" new growths at such an early stage.
      Someone out there (a plant morphologist, perhaps) knows what these
growths actually are, but the best explanation I ever received was that
they would start growing should something happen to the otherwise
healthily growing new growths. I never tested this hypothesis, but it
sounds valid. They are normal, if slightly disappointing when one
expects double the number of new growths than what they get!

      4) Coloration
      Many orchids will develop different coloration when exposed to
high light; some Phalaenopsis, for example, will turn purplish. This is
also true of species such as Brassvola nodosa. This is simply a sign of
high light, and general health; typically, it occurs in the spring, when
the trees that might otherwise provide shade are still defoliated. The
only caveat is to make certain that, since the plant is already given
such high light, conditions be monitored to prevent foliage burn from the
rapid temperature swings that occur this time of the year. If it is already
getting this much light, and it gets very hot in your growing area on
a sunny day, you are likely to burn the foliage.