Diagnosing and Treating Orchid Disease Symptoms

Orchids, like people, can also suffer from illnesses during their growth. Whatever the severity of the symptoms, this is something a beginnergrowing orchidsneeds to know. Generally speaking,orchiddiseases may be caused by the following factors: for example, the place where theorchidsare planted (or placed) has "insufficient air circulation"; damage from "chemicals" (pesticides or fertilizers); invasion by "bacteria," "viruses," or "insects." Here we can only offer some common symptoms for discussion with fellow beginnersgrowing orchids; as for correct identification, that requires considerably more knowledge and experience. (1) Withering pseudobulbs Orchids of any genus or species have pseudobulbs; the difference lies in the size of the bulbs. This condition occurs when the orchid plant has been "dehydrated" for a long time. The main causes are: insufficient humidity in the air; insufficient watering; poor root growth that prevents the absorption of water. (2) Flowers fading quickly The length of time aflowerstays in bloom depends on the variety. If it is much shorter than the normal blooming time, there is a problem. If it is only two or three days shorter, it may be due to climate, the blooming season, or the plant not being robust enough - no need to worry. But if the difference is too great, it may be caused by the following:cultivationenvironment changing too drastically (for example, orchids newly purchased from orchid-growing countries all show this phenomenon); the effects of transport vibration (most commonly seen when pollen is accidentally dislodged); invasion by harmful gases (such as excessive ethylene in the air); sudden shifts between hot and cold temperatures (depending on thecultivationseason and circumstances). (3) Leaves turning yellow If the yellowing leaves occur on old plants (especially newly transplanted ones) or on older leaves, and the yellowing is relatively slow, that is a natural aging phenomenon - the so-called effect of metabolism - and there is no need to worry. If the yellowing occurs on new leaves, the causes are as follows: too much sun exposure (shade-loving varieties should not be exposed to direct sunlight); damage from cold wind or frost; damage from inappropriate pesticides; lack of nitrogen fertilizer; damaged roots. (4) Leaf tips turning black This generally occurs from over-fertilizing (or fertilizer that is too strong). When this happens, stop fertilizing immediately and flush the soil in the pot with clean water. Other possible causes are: poor water quality; bacterial infection (the affected leaf should be cut off and a fungicide applied). (5) Spots on flowers This condition is often caused by the following: a sudden rise in temperature (the temperature should be lowered immediately); poor ventilation (ventilation should be increased to get the air moving). If this symptom is found, the diseased plant should be isolated immediately. (6) Root rot This is the most troublesome and most common phenomenon, with many causes: overwatering; poor ventilation, making thecultivationarea too humid; poor drainage; soil not renewed for a long time (in principle, it is best to replace it once a year); inappropriate fertilizing (too high a concentration or too frequent applications); spraying too heavy a dose of insecticide; poor water quality; small insects parasitic in the pot; improper planting methods, and so on. (7) Deformed flowers This phenomenon is commonly seen in the following situations: genetic factors (caused by cross-breeding); excessive use of sprouting-promoting chemicals; invasion by a virus; temperatures too high or too low during flower bud formation; damage to the flower buds from external chemicals. (8) Flowers, buds, and roots damaged by pests The most common are: small snails, slugs, ants, and the larvae of moths and butterflies. Insecticide should be sprayed regularly, with prevention as the priority. (9) Black spots on leaves These are generally caused by the following: intense light exposure after watering (the spots will not spread and only affect appearance); bacterial invasion (the spots will spread, and the affected leaves should be cut off). (10) White powdery substance or small brown specks This phenomenon often occurs under poor ventilation with ants living in the pot. It is mostly found on the undersides of leaves, flower stalks, and the crown of the plant. These are scale insects, caused by ants feeding on their secretions. When there are only a few, they can be scrubbed off with a small brush and clean water, then an insecticide sprayed, or the entire potted orchid can be soaked in insecticide water. Generally, treat once a week, for three consecutive weeks. Again, prevention comes first and treatment second. (Mai Fen)