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Photo Credit: www.OrchidPlants.info
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Orchid Insects and Pests
There are undoubtedly more orchid pests than there are species of
orchids. A lot of them are only found in specific areas. Others, such as
the few more likely ones you might encounter, are common and prevalent
all over the globe.
If you only have a handful of orchid plants growing in your home, you
may never have such unwelcome guests. However, if you grow many plants
in one area such as a greenhouse, and especially under crowded
conditions, keep an eye out for these:
Scale
There are a variety of scale insects that attack orchid plants and you
need to take immediate measures to eradicate any one of them. One of the
two most common scale found on orchids is soft brown scale. Initially,
when in the crawler stage, they look like tiny flat crabs, but quickly
mature to resemble little shiny brown, tan or greenish bumps which are
attached to leaves and pseudobulbs. This pest is readily visible in the
adult stage, when they form a hard domelike dark brown shell. They also
excrete a sticky substance which attracts ants and subsequently develops
an ugly grey mold-like fungus.
The other common scale is boisduval scale, also known as white or wooly
scale. They also have several stages of development which are difficult
to see at first. Boisduval scale first appear as small round raised
spots on the leaf or pseudobulb. These are the females, which later
develop a thin protective cover. The larger white males are more
conspicuous and you will usually find them in clusters, especially on
the underside of leaves. Most likely there are many more hiding in large
fuzzy colonies around and under the rhizome as well as under bracts and
dry sheathing. This is a very persistent critter and seems to be able to
survive repeated treatments by appearing again perhaps even a year or so
later.
First aid for both of these is to use an old toothbrush which has been
dipped in water containing a few drops of dishwashing liquid and gently
scrub to dislodge as many of them as you can see. Rinse the entire plant
thoroughly with clean water and let it dry. After that, a systemic
insecticide specifically geared towards scale should be used according
to directions. Applications may have to be repeated several times as
recommended.
Slugs and Snails
We hope you don't ever encounter slugs in your greenhouse. They
absolutely love orchids and will travel up the spikes to reach and chomp
on tender new buds. They are difficult to get rid of and even harder to
locate during the daytime since they are nocturnal and spend the day
hiding out in the sheaths and axils of the plant.
One method of control are slug pellets distributed on the floor of the
greenhouse. You don't want to put the stuff in the pots, because
moisture will degrade the poison and the remains will become a source of
harmful molds. There are a couple of deterrents you might try.
Slugs love beer almost more than new orchid buds! Place a saucer filled
with beer near the affected plants, you will find the drunken offenders
in the morning. Another method is to discourage slugs and snails from
dining on your newly developing blossoms. Wrap a small piece of fluffy
cotton around the stem of the inflorescence below the first buds. Snails
won't cross over the cotton and don't appear to have much interest in
the stem itself.
Red Spider Mite
Red spider mite is a serious and devastating pest in the greenhouse.
They attack mostly the softer leaved varieties of orchids such as
phalaenopsis, dendrobium and cymbidium. They are so miniscule in size
that they are difficult to detect with the naked eye. This is why
infestation most often is only noticed when leaf damage is obvious.
The first indication is when the leaf color develops a silvery white
sheen which soon turns yellow and the leaf will drop off. In severe
cases, you will actually see dirty grey webs. Rub your thumb over the
leaf of a suspect plant. Red spider mite leaves a reddish/orange
residue. You can do another test by tapping a leaf over a piece of white
paper. A good magnifying glass will bring them into disgusting focus.
Red spider mites like hot and dry conditions and are therefore most
often encountered and active during the summer months. Try to keep up
humidity by daily misting to help ward off this pest. If caught early,
fairly good results can be achieved with liquid systemic miticides
applied several times in succession.
Roaches, Flies and Ants
You will encounter any one or all of these at one time or another. Even
if you think you have a completely sealed greenhouse, there are many
ways these critters will find a way in. Look around and you will spot a
few, such as fan vents, doors, cooling pads and more.
Keeping a clean environment along with a regular pesticide spraying
program will keep them down to manageable populations. Just don't hope
to eliminate them altogether.
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