Rational disease of orchid peanut-sunburn disease

Sunburn usually occurs when shaded plants are suddenly exposed to strong sunlight, and sunburn occurs when new potted orchid cuttings are exposed to sufficient sunlight. After the top pruning, the leaves on the stubble are also prone to sunburn pain due to the removal of the top leaves because they were previously shaded by the top leaves. As the direct point of the sun moves back and forth between the Tropic of Cancer and the Tropic of Cancer, plants in a particular part of the shadow are not exposed to the scorching sun early in the year, and may be exposed to direct sunlight in the middle of the year, during which a particularly hot day can cause sunburn in the parietal leaves of young or mature plants. Vulnerable plants such as Phalaenopsis and Magnolia with small tongues and some varieties of Cymbidium are very susceptible to sunburn. But under very hot conditions, all orchids are not immune.

In general, heat only damages the epidermal cells on the front of the leaf, which often turn grayish white and light brown, while the reverse side of the leaf remains green.

Treatment: when burning occurs on the same day, there is no warning, the affected leaves do not need to be removed, the infected leaves are sprayed with 2 tablespoons of carbendan or thiram with 2L water to prevent fungal infection, then move the plant to a more shady place and spray with fungicide every other week for 2 to 3 weeks. In case it is not possible to move to a more shaded area, the affected plant should be shaded in situ to prevent sunburn from happening again.

Prevention: plants growing in shade should not be suddenly exposed to strong sunlight. It is necessary to move the shaded plants to a more exposed place, but the best thing to do is to do it step by step, not too suddenly, so that the plants have time to adapt to the heat. All newly planted ink orchids must be black before practice to prevent sunburn, and additional shading is necessary to prevent sunburn due to changes in the position of the sun at certain times of the year. (Liu Zhongjian)