Symptoms and Control Methods of Physiological Diseases in Orchids

Lower leaf drop is usually related to root diseases, leaf diseases and damage from scale insects; old age can also cause lower leaves to fall. Other non-pathogenic factors related to lower leaf drop are improper cultivation practices and water stress. For orchids planted in the ground, improper cultivation and water stress are the most common causes of leaf drop. When the soil has not been properly treated, and the roots of newly planted seedlings are not well covered by soil or ground cover, they cannot absorb enough water, resulting in water stress. The lower leaves then turn yellow, dry out and fall off. During hot weather, the rapid transpiration of leaves and the high-intensity evaporation from the soil mean that if the plant does not absorb sufficient water, water stress occurs; sustained water stress leads to lower leaf drop and inhibited growth, especially for newly planted plants. Prevention: Seedbeds for growing orchids in the ground should be carefully prepared, and newly collected plants should be carefully planted according to the correct method. Lower leaf drop can also be prevented by inter-row covering and regular watering to avoid water stress. If replanting is carried out during the rainy season, water stress in the newly planted plants can also be avoided. (Liu Zhongjian)