Orchid Pests – Pests That Affect Orchids
The pests that affect orchids are insects of the biting and sucking kind, as well as their larvae, and spiders that suck sap or eat the leaves and roots. This causes weakening or damage to the orchid to the point where it will die if nothing is done to put things right.
They will only occur on the young, soft shoots of orchids. These 2-3-mm long insects establish themselves in dense colonies at the tips of shoots or around buds.
Causes: draughts, open windows, or sifting in very dry, warm air.
Remedy: remove insects by hand and spray the plant with a plant protection agent. Repeat the procedure again in eight to ten days. Orchids grown in hydroculture can be treated with a systemic agent. In greenhouses, conservatories or even in plant windows, you can try employing gall midges and lacewing eggs.
Scale insects hide, along with their eggs, under a whitish-yellow to brownish layer of wax and are often discovered far too late. The larvae are minute, move very quickly and are generally not noticed at all. The plants most at risk are , , and . The pests will tend to colonize leaves and pseudo-bulbs.
Symptoms: secretion of honeydew; formation of sooty mould; yellow spots on leaves; dropping leaves.
Cause: air too dry.
Remedy: increase humidity immediately. Scratch off scales with your fingernails or with a thin stick. Wipe down plants with a lukewarm soap solution or with cottonwool balls dipped in spirit. If this is all to no avail, spray the plant with a paraffin-based oil or try a leaf-shine spray. Note: Generally, only hard-leafed orchids (e.g. Dendrobium kingianum) can cope with leaf-shine spray.
Symptoms: whitish, woolly or cottonwool-like waxy excretions; crippled growth of plant.
Cause: air too dry.
Remedy: paint affected areas with alcohol. Increase humidity. If necessary, employ plant protection spray.
Red spider mites
These pests are the nightmare of all orchid growers who own greenhouses. Unfortunately, they occur quite often and tend to like Cymbidium, Dendrobium,and Phalaenopsis.
Symptoms: silvery, mottled leaves which turn yellow later on.
Cause: dry air.
Remedy: make sure the humidity is increased. Use the plastic bag method. Twice a week, spray the plant with lukewarm water during the morning. Spray with a special plant spray intended to combat spider mites. Employ predatory mites in greenhouses or conservatories.
This 1-2 mm long, brownish-black insect has two pairs of folded, black and white wings. The almost invisible larvae tend to hide underneath leaves. Thrips damage the plant by sucking the sap from leaves, flowerbuds or flowers.
Symptoms: brownish spots on crippled flowers; deformed buds; the leaves look silvery, caused by air pockets in the puncture holes; brownish marks underneath the leaves; often black, shiny spots of excrement.
Cause: dry, heated air.
Remedy: spray with a suitable plant protection spray. Do not forget to spray underneath the leaves! Increase humidity immediately.
mites and root mites
Cyclamen mites do not often appear on orchids. They may suck the sap of buds or new leaf shoots of Paphiopedilum. Root mites attack weakened, sick plants and eat the roots from the inside out.
Symptoms: crippled growth of the buds, new shoots and leaf stalks; eaten roots.
Remedy: spray with an acaricide.
These are 4-7 mm long, black flies that tend to fly up at the slightest touch. Their larvae love humus-rich or peat-richand if there is nothing else better to eat, they will devour orchid roots.
Symptoms: damaged roots; sickly plant.
Causes: transmitted from other indoor plants; importation from outside.
Remedy: Mafu or Vapona strips or sticky yellow tags. Insert yellow tags into the compost of individual pots.
These creatures are 1-3 mm long, look like white maggots and jump about. Generally they are useful as they ensure the decomposition of dead parts of plants in the garden. In the confines of a flowerpot, however, they tend to consume the peaty particles in compost and then move on to attack the roots.
Symptoms: evidence of damage on the roots; crippled growth.
Cause: too much watering in the darker season of the year.
Remedy: during the mornings, rinse the compost several times in lukewarm water.
Slugs and snails
Slugs and snails often appear as night-time visitors in free-standing greenhouses. They are attracted by the humid warmth. As any gardener will tell you, they can inflict a great deal of damage with their voracious appetites.
Symptoms: eaten parts of plants; holes in leaves and bulbs; slime tracks.
Causes: carried in on orchids that have stood outside during the summer months.
Remedy: collect them, either early in the morning or in the evening. Sprinkle slug pellets.