Diagnosing Orchid Diseases

Orchid Diseases – Orchid Fungal Diseases

In most cases, fungi are parasites which attack already weakened plants and they will only appear if the orchid has been subjected to much stress through dry air, lack of light, sunburn or other outside influences. Fungi will often colonize the holes bitten in plants by other pests. Orchids can be infested with terrestrial Fusarium, rusts and moulds. Bad ventilation encourages infestation.

 

Fusarium

Fusarium spores are always present and may be transported along with dust. They come up from the ground to settle on the surface of the compost.

Symptoms: spots on leaves, crippled growth, decayed spots. Occurs most often in Miltonia, Odontoglossum and Zygopetalum.

Causes: “cold, wet feet”; too much fertilizer containing nitrogen; bad ventilation.

Remedy: remove diseased parts of the plant. Disinfect cut surfaces of the plant with charcoal powder. Dip the entire plant, including roots, in a fungicide and spray thoroughly with the same, then add fresh compost. Isolate the plant for the time being. Very badly infested plants will often not recover at all. As a natural measure, try spraying the entire plant with garlic tea.

 

Cercospora

A harmful fungus that typically attacks Dendrobium orchids.

Symptom: spotty leaves.

Cause: weakening of the plant through mistakes in care.

Remedy: as for Fusarium.

Orchid rust

This is a rare fungus which sometimes occurs in imported plants. Cattleya, Epidendrum, Laelia and Oncidium are particularly at risk.

Symptom: yellowish to rusty red spore colonies on the leaves.

Causes: humidity too high; infection in country of origin.

Remedy: isolate the plant. Remove all infested parts of the plant. Immerse the entire plant in a suitable protection agent and repot in fresh compost.

Rotting flowers

This is caused by the harmful fungus Botrytis which also attacks strawberries in gardens.

Symptom: spotty flowers.

Causes: too much nitrogen in fertilizers; draughts; leaves which remain wet for too long; infection from other indoor plants.

Remedy: remove affected parts of plants. Disinfect cut surfaces with charcoal powder. Spray plant with a suitable plant protection agent.

Black rot

diagnosing orchid diseases - black-rot Caused by Pythium and other species of fungi.

Cattleya, Laelicattleya and Laelia are particularly at risk.

It is generally young plants that are infested and which tend to tip over during the night.

Symptoms: weeping wounds along the edges of leaves and new shoots (soft rot); reddish spots on leaves; blackish-brown discoloration of the neck of the root; decaying patches on bulbs.

Causes: humidity too high; waterlogging; low temperatures.

Remedy: immediately remove all diseased parts of the plant. Disinfect cut surfaces with charcoal powder. Immerse the entire plant in fungicide and repot in fresh compost.

10. December 2010 by admin
Categories: Disease Control, House Plants, Orchids, Orchids, Plants | Tags: , , | Comments Off on Diagnosing Orchid Diseases

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