What are the methods for preventing and controlling orchid pests and diseases?

During their growth and development, orchids often develop yellow leaves or scorched leaf tips, which reduces their ornamental value. There are many causes of yellow leaves and scorched tips in orchids, mainly the following four aspects:

(1) Overwatering or underwatering. Orchids prefer a humid climate, especially higher air humidity. If water is insufficient for a long time and the air is too dry, the roots will shrink and their absorption function will weaken, causing water and nutrients to be in short supply, resulting in yellow leaves or scorched tips. Conversely, overwatering and long-term excessive moisture in the potting soil can easily cause root rot, yellow leaves, and even death.

(2) Excessive or insufficient light. When growing orchids, if the placement location is improper and light is too strong or insufficient, it can also cause yellow leaves, scorched tips, or scorched leaf margins.

(3) Fertilizer applied too concentrated. Orchids are suited to light fertilizer, not concentrated or raw fertilizer. If fertilizer is applied too concentrated at one time, especially excessive chemical fertilizer, it often damages the roots and then causes yellow leaves or scorched tips.

(4) Damage from pests and diseases. When orchid plants are attacked by pests and diseases, it can also damage leaves and roots, ultimately leading to yellow leaves and scorched tips.

In addition, unsuitable pH of the growing soil (soil tending alkaline), long-term failure to fertilize or repot and change soil, and environmental pollution can all easily cause orchid leaves to turn yellow, become withered and yellow, or have scorched leaf margins and tips. In response to the above causes, the following preventive measures can be taken:

(1) Watering should be scientific. Whether to water and how much to water should be determined according to the season, growth and development stage, and the dryness or moisture of the potting soil. Special attention should be paid to increasing air humidity and avoiding potting soil that is too dry or excessively wet and waterlogged for a long time.

(2) Fertilization should be reasonable. Apply light fertilizer skillfully, and never apply concentrated fertilizer or unrotted liquid fertilizer. On the morning of the second day after fertilizing, water once with clear water to dilute the fertilizer and avoid fertilizer damage.

(3) Light should be suitable. Orchids prefer semi-shade. In addition to allowing somewhat more sunlight in early spring and winter, shading measures should be taken promptly after summer begins to avoid direct strong light. It is best to grow them under a shade frame or in a shaded area of a building.

(4) Prevent and control pests and diseases in time. Prevent diseases and eliminate pests as early as possible, with special attention to controlling anthracnose, black rot, scale insects, etc.

(5) The soil used should be appropriate. Choose slightly acidic, loose, fertile growing soil, and pay attention to repotting and changing soil at the proper time, applying a ferrous sulfate solution once at regular intervals, and keeping the potting soil slightly acidic.