Integrated control techniques of summer rhododendron flower disease

In addition to the "big flower rhododendron", there are other varieties of rhododendron, such as Japanese rhododendron, Belgian rhododendron and so on. The former is Oriental rhododendron, while the latter belongs to rhododendron, which is suitable for potted plants. however, if the daily frost is not properly planted and neglected, it will easily lead to the following diseases:

1. Black spot-if the azaleas (including rhododendrons and all kinds of rhododendrons) are placed in places that are not ventilated and overcast for a long time, then it is easy to cause the disease in humid weather or excessive daily moisture; it is caused by a fungus that spreads through the air.

If the ambient air near the cultivation is polluted, it is also easy to spot the leaves. The spores of fungi will be scattered in the basin soil, and the hyphae will first grow on the old and weak leaves, which will spread quickly, causing the leaves to fall off from the bottom up.

2. Brown spot-in rainy days, the leaves are hot and humid, and the leaves are prone to small brown spots, resulting in yellow, withered, wrinkled leaves and then lost. The usual prevention and control methods are the same as dealing with black spot, increasing stronger scattered light, removing air circulation and drier places. Eight hundred times of "topiramate" or a thousand times of "plant protection" can be used for pesticide application.

3. Chlorosis-caused by lack of iron and emblem elements, or planting soil is too alkaline; several rusty iron nails can be buried in the soil, or a little ferrous sulfate can be sprinkled in the basin, one gram at a time.

4. Stem rot-the climate is cloudy and humid, which makes the fungi invade the cortex, cut off the transport of water and nutrients, and the leaves dry up. Every day, appropriate potash fertilizer should be applied, more light should be increased, and places with good ventilation should be moved.

Causes and control of rhododendron diseases in spring and summer

In addition to the "big flower rhododendron", there are other varieties of rhododendron, such as Japanese rhododendron, Belgian rhododendron and so on. The former is Oriental rhododendron, while the latter belongs to rhododendron, which is suitable for potted plants. however, if the daily frost is not properly planted and neglected, it will easily lead to the following diseases:

(a) Black spot disease if the azaleas (including rhododendrons and all kinds of rhododendrons) are placed in places that are not ventilated and overcast for a long time, then it is easy to cause the disease in humid weather or excessive daily moisture; it is caused by a fungus that spreads from the air. If the ambient air near the cultivation is polluted, it is also easy to spot the leaves. The spores of fungi will be scattered in the basin soil, and the hyphae will first grow on the old and weak leaves, which will spread quickly, causing the leaves to fall off from the bottom up.

(2) Brown spot on rainy days, high temperature and humidity, leaves are prone to small brown spots, resulting in yellow, withered, wrinkled leaves, and then lost. The usual prevention and control methods are the same as dealing with black spot, increasing stronger scattered light, removing air circulation and drier places. Eight hundred times of "topiramate" or a thousand times of "plant protection" can be used for pesticide application.

(3) chlorosis

Cause of occurrence

1. Illumination: the direct cause of leaf yellowing is the lack of chlorophyll, and the formation of chlorophyll requires light, and only sufficient sunlight can make the leaves appear normal green. Lack of light causes the leaves to turn yellow and the branches to be slender and weak.

two。 Nutrient elements: the formation of chlorophyll requires iron, copper, magnesium, nitrogen and other elements, when the lack of these nutrients, there will be chlorosis, and the soil generally does not occur lack of copper and magnesium, the common is iron and nitrogen deficiency.

3. Acidity and alkalinity: chlorosis can also occur in plants due to the alkalinity of soil or water. When the alkalinity increases, that is, the increase of pH value, it will seriously affect the root absorption of nitrogen and iron, resulting in iron deficiency, nitrogen deficiency and yellowing, which is characterized by the gradual yellowing and shedding of leaves from bottom to top.

4. Soil: the poor permeability of soil can also cause yellowing.

5. Fertilizer damage: Azalea root system is as thin as silk, the concentration of fertilizer is very strict, fertilizer and water must be light, too thick plants will appear growth retardation, thin leaves, yellowish leaves, suddenly fall off or gradually fall off, or even die.

1. For iron deficiency yellowing, iron elements in the soil should be supplemented. Ferrous sulfate can be sprinkled around the basin soil, each time according to the basin size, apply 1 to 2 grams, and then dissolve in the soil by watering. Also soluble in water irrigation, the concentration is 1%, once a week, several times in a row, until recovered.

two。 For soil and water, the water is acidified first (pH value test paper can be used to measure the pH). The easiest way is to neutralize the alkalinity of water with vinegar so that the pH value is between 5 and 6. The improvement of soil is the same as using ferrous sulfate to prevent the yellowing of iron deficiency.

3. For the chlorosis caused not simply by the lack of certain elements, but by the disturbance of the physiological function of rhododendron caused by improper management. At this time, one should immediately stop fertilization, ferrous sulfate should not be applied more, otherwise it is tantamount to making things worse. After the new root grows and the leaf color turns green, it still needs to be stable for a period of time, and fertilize only after the new branch is lignified, otherwise the old disease may recur. Second, there is no waterlogging. Improve soil permeability, control water consumption, make basin soil dry and wet moderately, that is, "dry but not crack, tide but not wet", in order to promote the emergence of new roots. Third, it is not exposed to the sun. Because the root system of the diseased plant is weak, the leaves are fragile and easy to wilt, so special attention should be paid to shading in summer and autumn, but it should not be too dark, especially in winter and spring and late autumn to increase light to facilitate photosynthesis. The fourth is to avoid plant flowering. If the diseased plant blossoms badly, the flower buds should be removed in time so as not to consume nutrients.

(4) the disease of stem rot is yin and dampness, which makes the fungi invade the cortex, cut off the transport of water and nutrients, and the leaves dry up. Every day, appropriate potash fertilizer should be applied, more light should be increased, and places with good ventilation should be moved.

Integrated control of diseases and insect pests in rhododendron special garden due to many varieties of flowers, luxuriant flowers and leaves, and long flowering period, rhododendron has been planted in plazas and road landscapes in recent years, playing an obvious role in beautification. But it is also vulnerable to dozens of diseases and insect pests and lose its ornamental. Over the years, many units have spent a lot of manpower and material resources on prevention and control, but often do not get good results. The main reason is that we have not really given priority to prevention. Through three years of investigation and research, we have explored some methods of comprehensive prevention and control.

1. The choice of planting site the cuckoo is a shade-loving plant, and the direct light of the sun is disadvantageous to its growth, so the cuckoo special garden had better choose a shaded place with trees, or take this into account when doing greening design, and deliberately configure trees in the special garden. 2. Soil rhododendron likes acid soil with good drainage, but because all special gardens and landscapes have to use cement for roads and paving, the soil of rhododendron planting land is hardened and alkaline, so it is necessary to replace the soil and add a certain amount of peat soil. 3. The planting of rhododendron is most suitable for planting in early spring or late autumn. if planted in other seasons, a shade shed must be erected, and the root system and soil must be evenly compacted, but it should not be too tight, and the soil surface near the rhizome should be curved, which can not only protect the superficial root system from cold damage, but also conducive to drainage. 4. Daily management of cuckoos 4.1 watering cuckoos require that the soil is moist but not wet. In general, rhododendrons planted in open fields can be watered every 3 days in spring and autumn, and at least once a day in hot summer. Daily watering, do not use alkaline water, watering should also pay attention to the water temperature should not be too cold, especially in hot summer, using supercooled water to penetrate, resulting in a sudden decrease in soil temperature, affecting root water absorption, interfering with plant physiological balance. 4.2 spray cuckoos like the environment with high air humidity, but some cuckoo special gardens are built on both sides of squares and roads, and the air flows quickly and is relatively dry, so it is necessary to spray water on cuckoo leaves or spray the surrounding air. Keep the air around the cuckoo garden moist, which is conducive to the growth of cuckoos. 4.3 fertilization in the late winter and early spring every year, it is best to apply some organic fertilizer to the rhododendron garden as base fertilizer. After the rhododendron blossoms from April to May, because the plant consumes a lot of nutrients during the flowering period, the new shoots grow with the germination of leaf buds, which can be fertilized every 15 days or so. After the ambush, most of the shoots have stopped growing, at this time is the high temperature season, the physiological activity is weakened, can no longer topdressing. After autumn, the climate is getting cooler, and there is continuous autumn rain, temperature and humidity is suitable for cuckoo growth, at this time can do the last fertilizer, generally not suitable for fertilization after winter. 4.4 pruning is an important measure in daily maintenance and management, which can regulate growth and development, thus making growth exuberant. Daily pruning needs to cut off a small number of diseased branches and weak old branches, combined with the crown shape to delete some overdense branches to increase ventilation and light, which is conducive to plant growth. The cuckoo garden should be inspected frequently, and if dead and diseased branches are found, they should be removed in time to reduce the spread of diseases and insect pests in the cuckoo.