DIAGNOSING PHYTOSTRESSES WHICH RESULT IN FOLIAR COLOUR SYMPTOMS
The following table is provided to assist growers and others in diagnosing a few problems which develop in the culture of tropical foliage plants.
| SYMPTOM | CAUSE |
| * General chlorosis of all leaves | Insufficient fertilizer, very bright light, high temperature. |
| * General chlorosis of youngest leaves | Lack of iron or manganese, plants held in dark for too long period; agricultural chemicals. |
| * General chlorosis of older leaves | Lack of nitrogen or potassium, high soluble salts, poor soil aeration. |
| * Leaf edges chlorotic | Lack of magnesium and potassium (lower leaves), high soluble salts, spider mite feeding, agricultural chemicals. |
| Areas between veins chlorotic | Lack of iron or manganese, spider mite feeding, sulfur dioxide pollution, agricultural chemicals. |
| Chlorotic spots (round) | Bacterial or fungal disease, agricultural chemicals. |
| Chlorotic spot (irregular) | Cold water, bacterial or fungal disease, virus or virus-like disease, agricultural chemicals. |
| Stippled or dot-like chlorosis | Spider mites, planthoppers, leafhoppers or thrips. |
| Mosaic-like chlorosis | Cold water, virus or virus-like disease, agricultural chemicals. |
| Water soaked or greasy coloured spots | Excessively high temperature, low air temperature, cold water contacting foliage, bacterial or fungal disease, foliar nematodes, agricultural chemicals. |
| Edge of leaf or tip of leaf dead | Potassium deficiency, excessive boron, high soluble salts, fluoride toxicity, high temperature, low temperature, plant became too dry, spider mites, bacterial disease, agricultural chemicals. |
| Spots or sectors of leaf blade dead | Cold water, leaf miner feeding, bacterial or fungal disease, foliar nematodes, agricultural chemicals. |
| Dead areas on both edge and internal portion of leaf | Excessive intensity, low air temperature, colored water, foliar disease, feeding from a number of pests, air pollution, agricultural chemicals. |
Additional Note from D.P.I.
* Before checking on insufficiency, firstly examine the tree for root rot, collar rot and mechanical damage (of lawnmowers, whipper snippers etc.)
DATE: January 1987
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