What causes orchid leaf diseases?
Admiring something always comes with reasons. As the foremost of the old varieties of red Huilan, Chengmei can be said to have been thoroughly described by earlier writers when it comes to appreciating the flower alone, but in my opinion, the taste of a flower, while the single bloom is certainly important, depends even more on flower color, fragrance, flower form (huashou), inflorescence, leaf posture, and the relationship between flowers and leaves...
1) Orchid leaves take on a yellowish tinge while growth remains normal: this is caused by excessive light.
2) Orchid leaves turn yellow and new shoots are smaller: excessive light, lack of nitrogen fertilizer and necessary humidity.
3) Old orchid leaves yellow and drop off: normal aging or caused by repotting.
4) Old orchid leaves yellow and drop off rapidly: overwatering too frequently, improper repotting and planting.
5) Tips of new orchid leaves are scorched: excessive fertilization, unclean potting medium.
6) Both new leaves and old plants have scorched tips turning black: excessive heat and dampness in the pot, with rotted roots among the root system.
7) New orchid shoots stop growing after emerging: there are rotted roots or unclean matter beside the new shoots; uncover the potting medium around the new shoots, remove the unclean matter, and growth will resume.
8) Orchid leaves have scorch spots with no yellow around the edges: sunburn spots from intense sunlight.
9) Orchid leaf tips appear scalded and shrunken: the water temperature for watering is too high; the air temperature is too high when watering; exposure to sudden rain showers during high summer temperatures, etc.
10) New orchid shoots rot at the core: after water is poured into the shoot core, the water cannot evaporate or be absorbed, and unclean potting medium breeds leaf rot disease, etc.
11) Orchid leaves have spots with water-soaked edges: excessive humidity, with pot moisture and air humidity combining to cause suffocation, accompanied by leaf rot pathogens. Poor ventilation and air circulation.
12) Orchid leaves have yellow-brown spots: caused by the roots being exposed to heat.
13) Orchid leaves have irregular yellow spots, with leaf mesophyll tissue necrotic and sunken: caused by viral disease, also known as "balas".
14) Orchid leaves have small yellow spots: caused by scale insects.
15) Orchid leaves show purplish-black while the underside remains green: caused by low-temperature frost. It can also occur with phosphorus deficiency.
16) Orchid leaves dehydrate and pseudobulbs shrivel: caused by long-term excessive dryness and dehydration in the pot.