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Pests and Diseases in Orchids

The common pests of Orchids are Ants, Aphids, False Spider Mite, Leaf Hopper, Leaf Miner, Mealy Bugs, Mollusks, Red Spider Mite, Rodents, Scale insects, Thrips, Weevils. The common diseasesof Orchids are Basal rot / damping off, Bacterial brown spot, Brown rot, Black rot, Root rot, Leaf Spotting. The common viruses of Orchids are Sooty mould, Cymbidium mosaic, Tobacco mosaic and yellow bean mosaic, Odontoglossum ringspot virus.

The common pests of Orchids:

Ants: Ants usually indicates the presence of aphids on orchids. Ants feed on the honeydew that is secreted by aphids. Furthermore they transfer scale from one plant to the other, they make nests in pots which breaks down the compost and prevent proper aeration. Make use of an appropriate organic insecticide and treat the entire plant.

Aphids: Aphids can be green, black, brown and even orange. They multiply rapidly in warm, dry weather and also attract ants with their honeydew secretions. The honeydew secretions also result in sooty mould. With minor aphid infestation you can spray aphids with a jet of tepid water or wash the infected areas of the plant by immersing it in a solution of insecticidal soap. For a serious infestation you may even resort to a general insecticide. (Tip: Check regularly for these pests can be quite persistent.)

False Spider Mite: These are slightly smaller than red spider mites and make their presence known by the silvery colored pitting that one can see on the top and underside of leaves. You can mist the top and underside of the leaves. You can also clean the affected leaves with insecticidal soap and water to kill adult mites. Or you could use a miticide. (Tip: Repeat the treatment every ten days to kill any eggs to prevent it from recurring.)

Leaf Hopper: These are tiny, white, sap-sucking flies that usually stay on the underside of leaves, flowers and especially new growth. The best counter for these pests is those sticky fly-traps or use an appropriate insecticide.

Leaf Miner: These are little grubs that is responsible for spreading virus-related disease that destroy leaves and stems of orchids. You should cut away any damaged stems and apply a systemic insecticide.

Mealy Bugs: This is a very common orchid pest. They are little oval shaped, grey-whitish fluffy-looking insects. They belong to the sucking insects that are often encountered on the underside of leaves and new growth. They even attack the orchid flower. Like aphids they also secrete honeydew which causes sooty mould on the orchid leaves. Make use of a cotton swab and clean the affected areas of the orchid with a mild liquid detergent or insecticidal soap to remove the adult mealy bugs in case of minor infestations. They are quite persistent and you might even find that you need to apply drastic measures incases of bad infestations. (Drastic measures could include cutting off an affected orchid flower if necessary.)

Mollusks: Snails and slugs are possibly the most common pests in this category. They favor seedlings and soft foliage plants; they even eat through root tips, flower buds and pseudobulbs of orchids. Since they are nocturnal their movements can be tracked by the silvery slimy track that they leave behind. You need to be vigilant. The best methods to counter these little pests are organic control – lure them to a feed in a saucer of beer or under a lettuce leaf, collect them by hand in the morning. You could opt for commercial slug and snail pellets, but this can be nasty to curious pets.

Red Spider Mite: This is another common orchid pest and likes to attack Cymbidium orchids and the Lyscastes orchids. Red spider mite is hardly visible to the human eye, but evidence can be seen in the web-like film on the underside of leaves. They are sap-sucking insects and destroy leaf cells. This result in the orchid leaves yellowing and dying. Mist the tops and undersides of orchid leaves regularly and prevent infestations. Use the same countering measures as for the false spider mite.

Rodents: Rats and mice can be very destructive as they enjoy eating the pollen of the orchid flower. They scamper up the stems to reach the pollen and thus shorten the orchid flower’s life. Make use of commercial poison and set traps for these critters.

Scale insects: These come in many varieties that attack orchids. Scale insects are usually quite mobile when young while the adult scale insects tend to rest on the underside of leaves or beneath the orchid leaf sheaths, either individually or in colonies. They are basically sap-sucking insects that leave yellow patches on the orchid leaves and also secrete honeydew which result in sooty mould. Ants can also be lured by these secretions. Make use of a soft brush and insecticidal soap and water to remove scale. Take care not to damage leaves. You can also make use of a 50:50 solution of water and denatured alcohol. With serious infestation you might have to repeat the treatment and use systemic application of organic insecticide.

Thrips: These are tiny winged insects. Grayish in color and they usually settle on the underside of leaves. They tend to chew up the orchid, scraping the orchid leaf surface for sap and thus causing scarring and discoloration. Make use of the appropriate organic insecticide to fight them off.

Weevils: They are hard-bodied beetles with a dull coloration. They chew into the soft tissue areas of the orchid plant. Weevil and caterpillar damage is rather similar. You should spray or dust the orchid with the appropriate insecticide.

The common diseases of Orchids:

Basal rot / damping off: This is a fungal disease that results in the withering of the orchid stems, especially young seedlings. Basal rot is usually a consequence of: failing to use clean pots or potting mix, overcrowding, or over-watering. You must apply fungicide to the infected orchids, repot them, reduce watering, and increase ventilation to alleviate symptoms of Basal rot.

Bacterial brown spot: This disease is a quick spreader and appears as a brown, watery blister on orchid leaves. It can kill orchids when the infection manages to reach the crown. The bacterial brown spot disease thrives in cold, wet conditions and develops when orchid leaves are allowed to remain wet. The most vulnerable orchid species is the Phalaenopsis orchid. The best remedy is to isolate the affected orchid and remove all affected leaves using a sterilized cutting tool. Spray the orchid with an appropriate bactericide. (Tip: Follow the manufacturer's instructions to the letter.) You should also move the affected orchid to a drier environment until you have the disease under control.

Brown rot: This disease manifests itself as a small brown spot on an orchid leave that grows large very quickly. Another symptom of brown rot infestation is the spice odor that infected orchids emit. Brown rot also has the ability to kill the orchid if it is allowed to reach the crown. The most vulnerable orchid species is the Paphiopedilum orchid. You can use the same treatment as for bacterial brown spot. (Tip: What also helps is a good dusting of cinnamon powder.)

Black rot: This specific type of disease affects the whole orchid plant. It manifests its appearance by the infected area turning black and watery. Over-watering is the main cause of black rot. The most vulnerable orchid species is the Cattleya orchids. You should remove all affected parts of the affected orchid. Spray with the appropriate fungicide and avoid over-watering.

Root rot: This disease is a result of fungal infection to the orchid roots. Orchids will manifest a root rot problem by showing a decline in health and the roots will turn brown. A main cause for root rot is over-watering the orchid and decayed potting mix, and even poor aeration. Make use of a sterilized cutting tool to remove all dead tissue, repot the orchid in a clean pot with fresh potting soil and treat with the recommended fungicide. Most of all avoid over-watering.

Leaf Spotting: This is an unattractive, but benign fungus that appears as small brown spots, sometimes black spots, on orchid leaves. Most orchid species are vulnerable to this disease. Make use of a recommended fungicide and spray the orchid following the instructions closely. Provide optimal growth environment for your orchids.

The common viruses

Sooty mould: This is a soft, black fungal growth that results from the honeydew secretions of aphids, mealy bugs and scale insects on orchids. Sooty mould reduces the amount of light that should reach the leaves and results in the ultimate deterioration of the orchid. You need to wash the orchid leaves with a soapy solution, or make use of a 50:50 solution of water and denatured alcohol. Try to get rid of the cause by getting rid of the pest that secretes the honeydew.

Cymbidium mosaic: This is a very common orchid virus that appears as a dark, sunken patch or streak on orchid leaves. The plants will continue to grow, but will be lacking in vigor, and may even affect other orchids. The best treatment would be to prevent the disease from spreading and destroy the affected plants.

Tobacco mosaic and yellow bean mosaic: Symptoms of these viruses are: orchid leaves becoming mottled with irregular patches of yellow and green, the orchid flower exhibiting streaky, dark coloration. At risk most are Cymbidium orchids and Masdevallia orchids. One answer: Destroy the affected orchid.

Odontoglossum ringspot virus: This virus appears as round blemishes on orchid leaves. These blemishes are usually concentric circles and eventually affect the orchid flowers which will appear deformed. One answer: Destroy the affected orchid.

Preventing orchid pests and diseases:

  • Prevention is better than cure: Prevent disease in your orchid
  • Be vigilant. Check on a regular basis for any visible sign of pest and disease infestation
  • Maintain a clean, well-balanced growing environment
  • Buy only healthy, quality plants from a reputable source
  • Quarantine all new plants for a minimum of two weeks before integrating it with an existing collection
  • Use only sterilized cutting tools
  • Only reuse pots that have been disinfected with a bleach solution
  • Do not reuse compost or potting soil
  • Do not water an orchid with the runoff of another

Tips for using insecticides:

  • Select the appropriate insecticide or pesticide for the specific affliction the orchid is suffering
  • Read the manufacturer's instructions and be sure to mix and apply the products precisely according to the instructions
  • Apply insecticide in moderate temperatures to avoid damage to the orchid
  • Keep pets and children away from the area while spraying
  • Make use of gloves and a face mask as well as goggles when applying spray
  • Wash any part of your shin thoroughly if it came into contact with the insecticide solution
  • Safely dispose of all unused mixture
  • Store insecticide out of reach of children and under lock and key

Ref: http://www.landscape-and-garden.com/orchids/care.aspx