Causes and Control of Leaf Tip withering and scorching of Orchid

The leaf tip of orchid is withered and scorched, which is one of the common diseases. It not only damages the integrity of orchid leaves, affects the ornamental value and economic value, but also seriously affects the healthy growth of orchid plants, and even endangers the life of orchid plants. After years of practice and exploration, it is considered that the withered and scorched leaf tip of orchid is caused by physiological diseases and infectious diseases. Most of them are caused by physiological diseases. It is broken down as follows:

1. Poor growth of Langen

It can be said that whenever there is an orchid plant leaf tip withered and scorched, there are different degrees of root rot phenomenon. There are many reasons for poor root growth.

1. Waterlogging damage:

It is mainly due to the fine texture of the orchid basin, slow water volatilization; the culture substrate is not rough enough, the drainage performance is low; watering too much. Orchids "like rain but afraid of waterlogging", "happy and moist and afraid of wet". But do not understand the word "moist" as moist, and pour the orchid like mud in a paddy field. It should be covered by the continuous rain and torrential rain, and the basin should not be watered until two or three days after the basin is dry. Orchid bonsai is good to choose rough pottery basin, try to use special tall tube with feet, basin wall porous, basin bottom with large hole orchid basin, such as fine texture porcelain basin, purple sand basin, it is best to try to drill more holes; on the other hand, the basin bottom must not be blocked with tiles, must be overhead. In order to enhance the permeability and hydrophobicity, the culture medium must strive to be rough, and the mud made from local materials should be mixed with broken bricks, burnt soil, or sterilized snake wood shavings, Chinese fir chips and other coarse plants.

2. Freezing damage:

Orchids belong to shade plants, which are not resistant to low temperature and frost. When the temperature is below zero, most orchids have varying degrees of freezing injury. If the root tip is frostbitten, gradually dried and wrinkled, and loses the ability to absorb moisture and nutrients, the temperature picks up in the next spring, the light increases, and the leaf tip becomes scorched without supply. Even the new buds germinated at the end of spring are unable to provide for the consumption of new shoot development because the plants are not fed, resulting in slow root growth and scorched leaf tips.

Another situation is that the simple greenhouse and on-site anti-freezing covered with plastic film, because it is unable to drain moisture and absorb moisture, the water vapor in the film drips back on the orchid leaves and freezes, as if it had been scalded by boiling water. If it is slightly frozen, it can be recovered, but the phenomenon of large area scorched tail gradually appears in late spring and early summer. Therefore, for the simple greenhouse and local film covering, moisture-absorbing cloth, blankets, sacks, straw curtains and so on should be hung in the shed.

3. Fat damage:

Orchids like to be fat but afraid of turbid. Not only the concentration of orchid fertilization should be low, the interval time should be long, but also the application amount should be less. Excessive and dense fertilization is easy to clear the orchid root and lead to leaf tip scorch.

On the other hand, orchids generally do not need to be planted under the base fertilizer; if you want to grow orchids, the proportion should be less, generally not more than 1%. Organic fertilizer without fermentation, ripening and disinfection should not be used as the basic fertilizer of orchid in order to prevent fermentation and scald roots in the basin.

4. High temperature damage:

In the hot season of midsummer and golden autumn, in greenhouses and plastic greenhouses, the temperature is as high as 30 degrees or even 40 degrees under the scorching sun, which is very muggy. The limited moisture on the site is consumed as soon as it rises, and it is impossible to reach the leaf tip. This causes the leaf tip, leaf edge and leaf tip to become scorched.

There is also a situation where the root tip of the orchid plant planted in a thin tube basin is close to the basin wall, and the high temperature and hot basin wall will also scald the root tip and cause the leaf tip to scorch. Therefore, in the high temperature season, we should seriously strengthen shading, ventilation, spray cooling, basin wall also need to spray wet.

5. Acid damage:

For the substrate that has not changed the basin for more than two years, due to the frequent application of acidic chemical fertilizer and other factors, the matrix is too acidic, which will also lead to root rot. The solution is:

Replacement of new substrates from ① seedlings

② was poured with 3000-fold white alkali water once to neutralize it.

6. Hormone damage:

Some people, in order to dwarf the orchid plant, apply dwarfing agents such as "doxoril". Because it is too toxic and has a long residual period, it makes the roots black rot, resulting in the loss of root function, and the leaves are not adequately fed and scorched tips appear until the whole plant dies.

7. the harm of lack of elements:

Some people often increase the proportion of nitrogen fertilizer in order to make the leaves green and sprout, so that the three elements of fertilizer lose the relative balance. The most common symptom of potassium deficiency is the appearance of scorched leaf edge and tip. Therefore, do not use fertilizer partial nitrogen too much, pay attention to the root supplement of potassium dihydrogen phosphate, you can also spread some "Reed grass ash" in the basin.

8. Diseases:

The most common root diseases suffer from root rot, black rot, soft rot, bacterial wilt and other root diseases, resulting in the loss of root function, leaf tip scorch and then the death of the whole plant. Therefore, whenever the development of new buds is slow or the leaves are out of mind, the roots should be explored. If problems are found, seedlings should be raised, washed, disinfected and replanted.

For this disease, the focus is on prevention, generally, the culture medium is not too wet, strive to be partial, not partial to nitrogen fertilizer. After the warm spring temperature rises, the root is irrigated with 800-1000 times liquid "Diexong" once every ten days, twice, and then applied once a season, which can effectively prevent it from happening.

2. Abnormal growth of leaves

1. Physiologically, due to the partial application of nitrogen, the leaves are too young and tender, and the stress resistance decreases; there are fertilizer damage caused by spraying fertilizer, too high concentration, too much application, and deposition of leaf tips; there are dry coke caused by low air humidity; there are frostbite caused by heat preservation in winter, water vapor deposition of leaf tips, and freezing temperature is too low; there are injuries caused by long-term contact with basin walls and culture media There are focal points caused by lack of potassium, etc., should be aimed at the cause, to avoid it. After spraying foliar fertilizer for eight hours, it is best to absorb clean water to wash off the fertilizer, which is more complete.

2. Infectious diseases:

① scorched tail disease: the disease is characterized by round or irregular brown spots, slightly sunken, and gradually become brown and withered.

② iron rust: the disease is characterized by many iron-brown, sesame-sized bulges on the dorsal surface of the leaves at the initial stage of the disease. when the speckles break, their spores will float with the wind and spread on all sides.

③ iron cannon disease: its disease is characterized by the appearance of disease spots at the end of the leaf; its shape changes from small to large, until it is closely linked into pieces, and its color changes from yellow to brown, and finally to dark brown.

The prevention and control method is to avoid partial application of nitrogen fertilizer; hastily over-close planting, orchid pot display is too crowded; once a disease occurs, cut off the infected part in time (should be expanded and cut one or two centimeters more) and burn it centrally; its drug prevention and treatment should pay attention to spraying to the back of the leaves, and it is required to spray every other day and continue for three times, it will be able to fully control the disease. The effective agents for its prevention and treatment are 1000 times of "Yili", 500times of "Yipudan", 500times of "Dasheng 45", 800times of "Haosujing" and 500times of "detoxification alum".

Third, how to distinguish between physiological diseases and infectious diseases

The scorched part of the physiological disease has the same color and lustre, and there are no spots, and there is no mildew release on the back of the leaf under the wet condition; the infectious disease is a little spot at first, which gradually expands into a piece and causes the whole section to scorch, and the spot color changes from light to deep, and finally blackens, and under the wet condition, the fog is released.