Pests and Diseases of Orchid

Pests and Diseases of Orchid

Diseases of Orchid:

Fungal Diseases of Orchid

Leaf Spot:

This disease is very common and can be found on almost all cultivated species or orchids.  It is caused by species of Glocosporium, Colletotrichum, Carcospora and Phyllostictina.
Spraying of Bordeaux mixture ‘6-6-50 or 4-4-50) will effectively control the disease.

Pythium Black Rot:

This disease affects mostly seedlings in community pots and is caused by Pythium ultimum.  Affected plants turn black and leaves start falling.
Infected plants should be removed and the remaining healthy ones sprayed with fungicide like Monoozeb @ 2.5 g/lit.

Root Rot:

The fungus Fusarium is responsible for this disease which causes the destruction of the root tissue.
The disease kills the seedlings and retards the growth of mature plants.  Affected plants should be treated with Zineb or tersan.

Orchid Wilt:

 This disease is caused by Selerotium rolfsti which affects mostly Cymbidium and Paphiopedilum plants.  The leaf base initially becomes yellow later turning brown. Affected leaves should be removed and plants repotted in fresh medium after treatment with protective fungicide like Pentachloronitrobenzene.  Treatment with Zineb or Natripheno is effective.

Pests of Orchid:

Mites:

There are minute insects which suck juices form the cells of leaves, leaving them specked with white.

These can be controlled with a 20% emulsion of DMC diluted at the rate of 1 pint per 100 gal.

Thrips:

Thrips are very small insects’ which feed on foliage or remain hidden in the flower buds.
Thrips that feed on orchid leaves have successfully been controlled by the use of DDT.

Scales:

Both armoured and soft scales attack orchids.  They attach themselves to leaves and suck the juice form the cells. 
To control the scale insects’, the use of the root extract of Derris, a plant which is common in Malaysia, is recommended.  Because of their scales, these insects get protection from the insecticides.

Plant Bugs:

Bugs injure orchids by sucking sap and causing pale spots on the leaves.
Good control could be obtained with the application of gesarol A (5 % DDT) @ 1 kg in 100 liters water with rhodiatox at 1:5000

Aphids:

Aphids suck the sap form plants and excrete honeydew on the now spikes and foliage.  They also transmit certain virus diseases or orchids.  Certain organic phosphates, parathion and Malathion give good control of aphids.

Meally Bugs:

The mealy bugs are easily identified by its soft and filamentous body with a covering of white powdery wax.

Spraying with 0.02% Parathion will control these bug species found on orchids.