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The best defense against pests and diseases
is growing healthy plants through sound culture and proper
sanitation. But even so, once in a while you may have to
deal with pests.
Pests
Fortunately not too many pests will affect
your orchids, but some of them will take determination to get
rid of. The insects that may affect your orchids are
mostly mealybugs, scale, aphids, fungus gnats, spider mites,
thrips and slugs / snails.
Check your plants after summering them
outdoors
Before bringing your plants indoors again,
check the leaves, under the leaves, around flower spikes,
behind flowers and just under the rim of the pot for any sign
of pests.
Chewed up leaves are a sure sign of damage
from slugs or snails.
If you have summered your plants outdoors,
even if you do not see any sign of insects you should consider
treating them against insects before bringing them in.
Check your plants periodically
It is a good idea to check your plants
periodically for any sign of insects. It is much easier
to eliminate insects before they severally infest your plants.
Scale
The two most common scales that may affect
your orchids are the soft scale and the armored scale.
Soft scale may hide in dried sheaths at the
base of pseudobulbs of Cattleyas or similar plants.
Remove the dried up sheaths to eliminate hiding places
for them. Remove as many of the scale as you can see, then
treat with an insecticide.
Hard scale looks like tiny turtles. They
will usually be under the leaves of Phalaenopsis or Cattleyas,
sometimes hiding in the pot. Remove as many as you can see,
then treat with an insecticide.
Mealybugs
They are white and look sort of cottony,
may be 1/4” in size. They can be on or under the leaves,
on flower stems, on buds, behind flowers, in the pot,....
Remove as many as you can see, then treat with an
insecticide.
Removing as many of the above insects as
you can.
For all of the above use a soft toothbrush
or cotton swabs to remove as many of the insects as you can.
Dip your toothbrush / your cotton swabs in alcohol before using
them to remove the insects.
Aphids
The mots persistent of them, as they
reproduce on a short, 3 day cycle. Usually found on new growth,
new leaves, on flower stems and flower buds, they suck the
juices out of the plants and can cause substantial damage and
leave marks on the leaves. Because they fly it is
difficult to remove them individually. In warm sunny
weather take the plant outside and use a garden hose to shake
them off the plant. Then treat with an insecticide.
Fungus gnats
Look like small black flies. Are mostly
hiding in the pot and fly our when you water. They are
attracted by potting material that stays damp and by decaying
plant material (dead roots, leaves,...). They feed mostly
on dead plant material but they may attack roots, especially
those of Cymbidiums. Because they hide in the pot you can not
remove any. You have to treat them by immersing the pot in an
insecticide solution.
Spider mite
Are very small and can not be seen
individually without a magnifying lens. You can detect them by
looking under the leaves for tiny silvery pits where they have
sucked the plant juices. Another way to see if they are any is
to place a white paper towel under the leaf and rub the leaf to
make them fall on the paper towel. Spider mites will thrive in
dry (too low humidity) environments. The best defense is
maintaining reasonable humidity, but if you have spider mites you’ll have to
treat them with an insecticide / miticide. For best results immerse
the pot in an insecticide / miticide solution.
Thrips
They do not occur frequently, but if they
do, you’ll notice it because of deformed or spotted
flowers. They are difficult to eradicate because they tend to
lodge in the flower buds and under sheaths where they are
protected from insecticide sprays.
Caution - Warning
If you are going to use commercially
available pesticides please always follow the
directions on the label. Some
of these insecticides are very
potent and you should make sure to apply all required
precautions against poisoning
yourself, others around you or your pets.
You can prepare a safe, effective
insecticidal soap by mixing 1 teaspoon of a mild liquid
dishwashing detergent (the 409 cleaner, regular, works very
well) to a quart of lukewarm water.
How insecticides work
Systematic insecticides are to some degree
absorbed by the plant and may offer residual protection for a
few weeks. Systematic insecticides tend to be more
dangerous than other insecticides.
Many insecticides kill only the adult
insects, not necessarily the eggs or the larvae (immature
insects).
Insects develop resistance to insecticides.
What this means is that some of them are not affected by
the insecticide and these will reproduce. Treating these
with the same insecticide will not kill them.
To avoid resistance you should consider
rotating insecticides, that is you make the first application
with one insecticide, the second application with another and
the third one either with the first insecticide or with a third
one. Rotating is not necessary with the insecticidal soap you
prepare because this insecticidal soap works by suffocating the
insects.
Treating for a limited infestation
If the infestation is not excessive, spray
thoroughly the new growths, leaves (both sides), flower stem,
back of buds and flowers with the insecticidal solution.
Treating severe infestations
If the infestation is widespread dip the
hole plant for 15 minutes of so in the insecticide solution.
For the treatment to be effective you have
to treat the plant (spraying or immersing) 3 times, at intervals of
one week (intervals of 3 - 4 days for aphids).
The reason you need to make more than one
application is because the insecticide will kill the adults and
a few days later the eggs will hatch and the cycle restarts
unless you treat again to kill the hatches. Most of the
time three applications one week apart (3 - 4 days apart for
aphids) will eliminate the insect population.
Caution !
If you are going to immerse plants in a
solution :
do it only on sunny days; if the
weather is cool, cloudy or rainy, you’ll be much better
off waiting a day or two before treating your plant(s),
do it early in the day; this
will allow any water that got in between leaves or new growth
to evaporate before nightfall,
do it with room temperature or
lukewarm water as a difference of 10 degrees or more between
the temperature of the water and the room temperature may cause
injuries to the plants.
Slugs
These are tough to treat as they emerge at
night. In the old days the products to treat them were
base on formaldehyde, a noxious product. Today you can
treat them with a very effective and safe product called
sloggo, available either in granular or liquid form.
The product is available from Monteray Lawn
& Garden Products, Fresno, CA (www. montereylawngarden.com;
Tel. 559-499-2100).
Viruses
Occasionally you may come across a plant
that has a virus. This may manifest itself by concentric
or elongated black or brown or discolored circles on the leaves
or black streaks on flowers and leaves. These will be
repeated on all leaves / flowers. New leaves / flowers
will at first appear free of it but as they age the virus will
manifest itself. Unfortunately there is nothing you can
do but discard the plant.
Bacterial and fungal diseases
These will appear if water stays in between
leaves or if the potting material stays soggy, especially when
the night temperatures are cooler (fall, winter, spring).
You can treat these with fungicides like RD
20 or Physan 27, but the best way is to avoid these problems by
practicing proper culture.
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A Comprehensive Guide to orchid Culture
Venamy Orchids
1460 Route 22 Brewster, New York10509
Toll Free
1-800-362-3612
Fax
(845) 279-2682
venamy@orchidsusa.com
Copyright 2002
Venamy Orchids |
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