What are the reasons for yellow orchid leaves? How to deal with it?

Many friends are prone to the problem of leaf yellow when raising orchids, and watering orchids is the key, so why is there leaf yellow? What are the reasons for yellow orchid leaves? How to deal with it?

The reasons for the yellowing of orchid leaves can be divided into three types: emergence, withdrawal of grass, diseases and insect pests. Emergence and withdrawal of grass are the yellowing of leaves caused by the physiological phenomenon of orchids. Emergence and withdrawal of grass are two different development directions in the process of orchid growth, so it needs to be talked about separately. This article will be introduced in detail around these three aspects, so that orchid lovers can have a more comprehensive and in-depth understanding of the yellow leaves of orchids.

1. Yellowing of orchid leaves caused by performance

The so-called performance refers to the appearance of colored lines or patches or spots on the leaves of bluegrass. This genetic change phenomenon of colored lines or patches and spots is called "art" in the industry. It is the orchid that has "evolved" in the normal growth process. Those with yellow lines are called "chimera grass" or "silk grass", and those with yellow spots and patches are called "patches". This kind of orchid is collectively referred to as "Ye Yilan" or "linear Yilan". The yellow leaf art of orchids can be divided into five common colors: yellow, white, gold, red and black.

Some orchids appear early and some late. According to the different time of orchid leaves, this phenomenon is divided into three categories in the industry: first bright art, then dark art, then bright art. To put it popularly, the yellow leaves of orchids are called "first bright art" as soon as they are unearthed; at the beginning, those that slowly turn green are called "first bright and then dark art"; at first, they are green, and those that slowly turn yellow later are called "Hou Mingyi".

Orchid leaves appear yellow lines or patches, when the leaves are still vibrant, glossy, will not wither, the yellow parts are very bright, and there is a strong contrast with the green parts, most of them have a very obvious dividing line, white is white, yellow is yellow, each goes its own way, if there is a yellowish brown dark color mixed with it, there is no luster, the leaves wither and wither, and the lack of vitality is not artistic. It should be considered that the leaves are yellowing caused by grass withdrawal or diseases and insect pests. If it is caused by the orchid leaves yellowing, we do not need to worry, do not need to deal with, normal breeding.

2. Yellowing of orchid leaves caused by grass withdrawal

Orchid is a perennial herb with a normal life of about 3-5 years, and a well-cultivated orchid can live for more than 5 years. After reaching its lifespan, the orchid will quickly wither and die, and the yellowing of leaves belongs to the normal withdrawal of the orchid.

The normal withdrawal of orchid grass is shown from the bottom and outermost leaf nail and leaf tip of the orchid plant, from the outside and inside, from top to bottom, the whole leaf yellowing rapidly, the longer the time, the darker the color, and gradually become yellowish brown, brown, until withered. We have no way to deal with this situation, waiting for the leaves to wither and cut off.

Some bluegrass can not reach the normal growth life due to improper planting and management, and the grass retreats early in 2-3 years. The number of bluegrass seedlings is less and less, and the orchid leaves are sparse, which can not achieve the purpose of reproduction and ornamental.

Abnormal withdrawal of orchid grass is generally caused by improper cultivation or failure to keep up with nutrients and water, because the false bulbs of orchids are closely linked and share nutrients and water, so when the nutrition and water needed for new seedling growth and flowering can not keep up with, if the old grass is attached, the old grass will transfer its own nutrients to the new seedlings and buds for their growth, which will cause the leaves of the old orchid seedlings to turn yellow. It is also shown that starting from the bottom and outermost leaf beetle and leaf tip of the orchid plant, from the outside to the inside, from top to bottom, the more nutrients the new seedlings and buds need, the more serious the yellowing of the old seedlings will be, and the serious ones can directly lead to the death of the whole old grass. If there is no old grass, if the root system is too small and too poor, it will lead to nutrients and water can not keep up, improper cultivation will lead to rotten roots, but also lead to yellow leaves and seedlings.

The treatment method of abnormal withdrawal of orchid grass: the number and integrity of the roots of new seedlings should be considered when dividing seedlings or selecting orchid grass. The more complete the roots of new seedlings, the stronger their ability to produce nutrients and absorb water. There is no need to rely on old grass to grow through weeding. If you want to separate new seedlings, it is recommended that new seedlings have 3 or more roots. If the new seedling has too few roots and is careful when dividing the seedling, we should choose the old grass with developed root system to divide it together. If the root system of the new seedling is developed and the root system of the old seedling is poor, it should be said that the old grass should be cut off and planted separately, and the granular plant material with good air permeability and stable character should be selected when planting, and the orchid should be fertilized appropriately during the peak growing season of orchid seedlings. Generally, in spring and autumn, it is necessary to apply thin fertilizer frequently and put it in a ventilated place after planting. Foliar fertilizer and root fertilizer can be used to supplement nutrients in the peak growing season of orchids.

3. Yellowing of orchid leaves caused by diseases and insect pests

1. Yellowing of orchid leaves caused by diseases.

The common diseases that can cause orchid leaves yellowing are anthracnose, soft rot and stem rot. Anthracnose is also known as black spot and brown spot on the surface of orchid leaves, which is characterized by yellowish brown spots in the middle and yellow edges, some accumulating and some scattered, and the disease spots can heal each other to form large spots, and sometimes break longitudinally, resulting in perforation and different sizes of orchid leaves. Diameter 1~20mm are mainly caused by high temperature and humidity, poor ventilation, diseases caused by fungi, infectious, can spread with the wind, diseased seedlings, plant materials, orchid pots and so on.

Stem rot is characterized by orchid leaf base yellowing, then gradually browning and blackening, yellowing from the heart leaf, spreading from the leaf base to the top of the leaf, at the same time, the false bulb shrinks and yellowing until it dries up. The disease is also a disease caused by fungi and is also contagious. it can also spread with the wind, diseased seedlings, plant materials, orchid pots and so on.

The soft rot disease shows that the leaves of the orchid begin to turn yellow at the base, appear small brown spots like water stains, then expand rapidly, and finally appear foul-smelling dark brown rotten patches, which fall off with a gentle pull of the hand. this is mainly caused by wound infection and non-evaporation in time, which is not contagious.

Prevention and treatment of the above three diseases: fungal diseases should pay attention to plant ventilation, environmental ventilation, avoid high heat and humidity environment, bacterial diseases should avoid orchid plant wounds, wounds should be disinfected and sealed in time, and seedling cutting tools must also be disinfected; commonly used drugs caused by fungi are carbendazim, chlorothalonil, methyl topiramate, etc. The commonly used drugs caused by bacteria are copper preparations such as streptomycin, copper hydroxide, king copper, amber fertilizer copper and so on.

2. Yellowing of orchid leaves caused by insect pests

The common pest that can cause the orchid leaves to yellowing is the red spider of mites. After the red spider sucks the leaves of the orchid, it will make the leaves of the orchid appear dense yellow spots, which cannot be washed off with water. It seems that it is the "sun spot" formed by malnutrition, too strong light, withering disease, dust or long-term watering moss attached to it, and some beginners still think that the orchid has mutated and appeared spot art. Red spider is not a common spider in our daily life, but a kind of mites, the individual is very small, less than 1 mm, the shape is round or oval, and the color is orange or reddish brown, which is very harmful to orchids.

Prevention and treatment of red spiders: in the opening season of new buds of orchids, as long as there are signs of red spider disease, it is best to spray insecticides to all orchids, especially pay attention to hit the new buds, and apply them again every 10 days or 15 days. generally continuous application of two to three times can effectively control the disease, can be used 1000 times EC, 2 times in a row, 7-10 days apart. The ideal control effect can be achieved by uniformly spraying 4000-5000 times of mite danger (800-1000 jin of water per bottle), 2000 times of diclofenac EC, 2000 times of mimetijing wettable powder, 2000 times of diclofenac EC, 1.8% of paraben EC and so on.

3. Yellowing of orchid leaves caused by fertilizer damage

The yellowing and blackening of the tip of new leaves is generally caused by excessive fertilization or high concentration, such as hypertrophy of new leaves, scorched yellow of leaf tips, uneven surface, scorched and dry old leaves, black and carbonized roots, severe rot of orchid roots and pseudobulbs, and death of the whole orchid.

Fertilizer damage prevention and treatment methods: when orchids are on the pot, base fertilizer should be applied according to the growth of orchids, grass down the mountain, weak grass, divide old grass, ripe strong grass and base fertilizer should also be appropriate, base fertilizer must be fully fermented, should be put in the lower part of the basin, it is best not to be in direct contact with the orchid root, so as to avoid root injury. Usually fertilization must be thin fertilizer frequently, less chemical fertilizer, the use of chemical fertilizer needs high dilution, dilution ratio in 3000-5000 times is appropriate, if found heavy pot soil, orchid leaves scorched tip, withered leaf phenomenon, should immediately turn the pot, wash the orchid plant, cut off the rotten roots, cool and dry, change the plain soil to replant.