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Orchid
Ailments
Leaves
Yellowing Leaves:
This is a normal aging process if only old leaves on backbulbs are
involved. If newer leaves yellow and soften, look for:
- too much
light
- low temperature
- lack of
nitrogen (especially in bark)
- loss of
roots
Blackened
Areas on Leaves:
The sudden appearance of brown then black areas on exposed surface
of leaves on a bright, hot day, may be sunburn. Check shading; if
blackened areas increase in size, it might be bacterial or fungal
disease. Cut off diseased area, treat with fungicide such as natriphene,
isolate plant, and dry it off.
Shriveled Pseudobulbs:
A sign that the plant is losing water content, it can be caused
by:
- low humidity
- underwatering,
dry medium
- loss of
roots
Blackened Tips or Ends of Leaves:
This could be caused by:
- overfeeding,
especially in cymbidiums -- cease fertilizing and flush plant
thoroughly with plain water
- excessive
soluble minerals in water -- have water analyzed
- leaf dieback,
a fungal infection -- cut off blackened areas and treat with fungicide
Brown
or Black Streaking or Mottling of Leaves:
This could be a virus infection. Send a leaf to your nearest agricultural
experiment station.
Small Spots on Leaves, Reddish Brown Turning Black:
Probably a fungus infection favored by warmth, high humidity and
poor light. Reduce humidity or dry off affected plants and treat
them with fungicide.
Flowers
Deformed Flowers
If deformed flowers are produced each year by a plant, it is probably
inherent. Destroy the plant.
An occasional
deformed flower can be caused by:
- high temperature
and low humidity when buds were developing
- mechanical
or chemical injury to bud
- nonrecurrent
and unexplained anomaly in bud development
- virus infection.
Isolate plant
Rapid Wilting of Flower:
If dorsal sepal wilts or dries early, or entire flower "goes
to sleep" shortly after opening, it could be caused by:
- air polluted
by ethylene or other gas
- too sudden
a change in climate
- pollination
by an unknown pollinator
Spotting of Flowers
Light brown or pinkish dots and spots on flower after opening usually
indicate fungus, Botrytis, or sooty mold. Reduce humidity, increase
ventilation or air movement, remove spotted and old flowers from
greenhouse.
Punctures in Flowers
Denotes presence of:
- aphids,
soft-bodied sucking insects; or
- thrips,
small chewing insects
Spray with
malathion.
Bruises on Flowers:
Either mechanical damage or red spider mites.
Chewed or Eroded Flowers, Buds or Roots:
Shows presence of:
- slugs or
snails -- use dust or bait; or
- cockroaches
-- use diazinon or Sevin on ground, on plants and pots
Color mottling of Flowers:
This could be a color-breaking virus. Isolate plant and get an experienced
opinion; destroy the plant if virus infection is confirmed.
Roots
Loss of Roots:
Numerous causes, difficult to diagnose:
- overwatering
- black rot,
an infection of Pythium. Soak in natriphene solution
- slugs or
snails. Dust with metaldehyde
- excessive
salt content of water
- potting
medium old and broken down. Repot after soaking plant in natriphene
solution
Entire Plant
White Cottony Mass or Gray, Brown, Blackish Crust on Underside of
Leaves, on Flower Stem, in axils of Leaves, etc.:
Mealybug or one of the many scale insects. Scrub with soft toothbrush
dipped in malathion. Spray greenhouse regularly with malathion.
This chart is reprinted from Growing Orchids, the 1993 Revised Edition
of the American Orchid Society Handbook on Orchid Culture.
Read how to Raise Healthy Orchids
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