NORTH OF ENGLAND ORCHID SOCIETY

Slugs, even if you think you haven't got any problem with these night-time assassins, you should always be vigilant for their silvery trails, sprinkle at regular intervals with a good slug liquid, and if you feel adventurous, take a torch-light trip into the growing area after dark, a good well aimed boot is something they have not grown immune to.

Weevils, when you wonder why there is suddenly a hole in one of your best grown leaves, or chunks missing out of its margin, then most likely you have weevils, arm yourself with a bottle of something suitable from the garden centre and follow the instructions.
Its no use spraying the once, you must have strict regime of spraying every 5 days or so over a period of three weeks to eradicate most pests and their eggs as they hatch.

Common Scale.
There are two types of scale which you are likely to encounter when growing orchids;- The first one attacks Phalaenopsis in particular, and can migrate to most other soft leaved plants, look on the underside of the leaves for these hard brown limpet like creatures, if you have only one or two, wipe them off with a cloth soaked in methylated spirits, or resort to a systemic insecticide regime as mentioned in the above paragraph, systemic insecticides act by being absorbed into the plant tissue, effectively making the plant poisonous to its attacker, but they should be used with care, do not exceed the stated dosage to avoid damaging the plant.
The other can be very nasty, and primarily has a taste for Cattleyas and their cousins, but can adapt to devouring other orchids such as Vanda's, this is:-

Boisduval scale.
A very fancy name for a real horror, you may notice flat round scales on the underside of the leaves, which if left unattended will produce a whole shipment of what appears at first to be a white fungus or mealybug, these are the nymphs by the thousand, and they are setting off to desiccate the rest of you collection.

The trouble we have in the UK is that it is a tropical insect, and many of our pesticides do not treat the problem, one we have found to be of use recently is Doff, you may have to search around to find it, it is very effective against this type of scale, and several other pests as well, you will probably have to give the plant a good cleaning after a couple of weeks or so for aesthetics. Prior to treatment, take an old toothbrush, dipped in methylated spirits, and having removed any old sheaths ( papery coverings from around the pseudobulbs), scrub gently to remove the majority of the adults.

Mealybug
Usually appears as a cotton wool ball around leaf axils, or inside the sheaths of new shoots, the above fungicide pesticide soon sees them off, but again if its very localized, then methylated spirits on a cotton bud sees them off wonderfully.

Thrips, greenfly, blackfly, spider mite.
They all find a niche somewhere, the latter is another difficult customer to deal with, and in addition to spraying, it is a good idea to wipe the leaves and stems of infected plants with a methylated spirit soaked cloth, every few days if necessary to kill the eggs.

SPOTS AND DISEASES.
Orchids can fall foul of leaf rot, mildew, botrytis and many other pathogens, by and large, providing there is a good air movement around the plant, and that by nightfall the leaves are fairly dry, then fungal infections should not be a problem, and correction of the bad condition, along with a fungal spray (check with the garden centre that it is safe for orchids) should do the trick, a fast fix for a localized leaf infection is to dust a little cinnamon onto the infected area ! It is very difficult if you have a plant suffering from a virus disease to identify which particular type it is, and most likely a useless exercise anyway, as viruses are almost impossible to cure, thankfully, providing you are hygienic around the growing area, and that any tools used on the plants are thoroughly sterilized after use between different plants, you should not encounter this type of problem. Return to top of page

SYMPTOMS.

POSSIBLE CAUSE

Irregular markings on leaves, discolored or uneven patches on flowers

possible viral infection

Uneven pieces removed from leaf border

weevils

Un-natural silvery underside to leaves

spider mite

Silvery trails on plants and benches

slugs or snails

Holes in leaves or flower stems or flowers

slugs or snails

Dark mildew on leaves, hard limpet creatures underside of leaves

common scale

Cotton wool type of stuff ( brownish creature inside of mass)

mealybug

Flat scales on mainly underside of leaves and or tiny white fluffy masses

boisduval scale

Depressed dark spots possibly with lighter ring round them

fungal infection

Limp flaccid leaves on Phalaenopsis etc.

root problems

Dark brown or whitened patches on leaf

sunburn

Yellow or very light green leaves but plant flowers

too much light

Dark green leaves but plant does not flower

too little light

Flower buds develop then turn yellow and drop off

shock

Leaf tips turn brown

over feeding

Honey dew on leaves

greenfly

Plant falls out of pot

earthquake