Detailed Explanation of Key Techniques for Preventing and Controlling Common Diseases and Pests of Azaleas
1. The main diseases of azaleas include root rot, brown spot, black spot, leaf blight, iron deficiency chlorosis, and so on.
(1) After an azalea is affected by root rot, its growth weakens, the leaves wilt and dry up, water-soaked brown patches appear on the root surface, and in severe cases soft rot occurs, gradually rotting and peeling off the bark, with the xylem turning black. This disease is most likely to occur under conditions of high temperature and high humidity.
Prevention and control methods: Before repotting, strictly disinfect the culture soil, and keep the soil loose and moist so that it has good permeability, avoiding water accumulation. If an affected plant is found, promptly deal with the diseased plant and the potting soil. During treatment, the diseased plant can be washed with a 0.1% potassium permanganate aqueous solution or 2% ferrous sulfate, then rinsed with clean water and repotted. A solution made from 70% thiophanate-methyl wettable powder diluted 1000 times with water can be sprayed on the potting soil to cure it.
(2) Brown spot is one of the main diseases of azaleas. When the disease first appears, small brown spots appear on the leaf surface and gradually develop into irregular large spots. Many small black or grayish-brown spots form on the lesions, causing the affected leaves to turn yellow and fall off, affecting flowering in the current year and the development of flower buds in the following year. This disease often occurs during the plum rain season when humidity is high.
Prevention and control methods: Usually pay attention to giving the plants ventilation and light, preventing excessive humidity, and apply more organic fertilizer and mixed nitrogen-phosphorus-potassium fertilizer to enhance the plant's resistance to infection and its growth capacity. If diseased leaves are found, promptly remove them and burn them in a centralized manner. In the early stage of the disease, spray 0.5% Bordeaux mixture or 0.4 Baume degree lime-sulfur mixture, and add 4% flour to increase adhesion. Leaf spot and black spot can also be treated by the same method.
(3) Iron deficiency chlorosis often occurs in areas where the soil is alkaline. When the condition is mild, only delayed greening of the plant appears; when severe, the leaf tissue can all turn yellow, and the leaf edges become scorched and withered. When the disease occurs, it is most obvious on the leaves at the top shoots of the plant, and is generally caused by internal iron deficiency.
Prevention and control methods: Change the iron-deficient nature of the soil and reduce soil alkalinity. Apply more organic fertilizer to improve clayey soil. For iron-deficient plants, directly spray 0.2%-0.3% ferrous sulfate solution. You can also use chopsticks to poke several holes about 15 cm deep in the soil around the plant, slowly inject a 1:30 ferrous sulfate aqueous solution, and fill the holes, in order to increase soil acidity and reduce alkalinity.
The occurrence situation and environmental conditions of azalea black spot are similar to those of brown spot, and similar methods can be used for prevention and control.
2. Common insect pests of azaleas include: red spider mite, lace bug, aphid, short-bearded mite, and so on. Red spider mites are tiny in body size but cause serious harm to azaleas. This type of pest is most likely to appear when azaleas are grown on high-rise floors.
Prevention and control methods: Carry out manual capture and killing. For chemical insect control, spray 5 Baume degree lime-sulfur mixture, or use equal parts of walnut leaves, oleander leaves, and sweet wormwood, crush and soak them to extract the liquid, dilute with water and spray. Spraying 1000-times-water dichlorvos solution to kill them is also a good method.
(1) The adult lace bug is small and flat, about 4 mm long, black, and is one of the most serious pests harming evergreen azaleas. It often pierces and sucks leaf sap on the underside of leaves, causing yellow-white spots on the upper surface at the damaged areas, making the leaves fall off, weakening the tree vigor, and affecting growth and flowering. Azaleas in greenhouses are extremely prone to this insect.
Prevention and control methods: Mainly use chemical spraying to kill them. You can spray 90% trichlorfon technical material at 1000 times dilution, or 40% omethoate emulsifiable concentrate at 1500 times dilution, or 50% fenitrothion emulsion at 1000-1500 times dilution for prevention and control.
(2) Aphids mainly harm the young branches and leaves of azaleas. In mild cases they can cause the leaves to lose their green color; in severe cases they cause the leaves to curl, become hard and brittle, and be unable to absorb nutrients, affecting flowering.
Prevention and control methods: Usually pay special attention to aphids during the overwintering period. After winter begins, spray 5 Baume degree lime-sulfur mixture once on the plants to eliminate overwintering eggs, and remove weeds near the flowers to eliminate the source of insects. During the period of aphid damage, use 40% dimethoate or omethoate diluted 1200 times with water to make a solution and spray continuously for treatment; results can be seen after 3-4 times.
(3) The short-bearded mite is one of the important pests of azaleas. It often pierces and sucks sap near the main veins on the underside of leaves, causing many oil-soaked patches to form on the leaf underside, and finally causing the leaves to fall off. This pest is obovate, about 0.3 mm long, flat in body, with body colors of red, dark red, and wood red, irregular black spots on the back, and irregular black patches on the sides. This pest is most commonly seen in summer when the weather is hot and dry, and decreases immediately when rainfall is abundant.
Prevention and control methods: Spray 0.5 Baume degree lime-sulfur mixture once each in mid-to-late October and early spring in March, or spray 25% insecticidal water agent at 500 times dilution; the effect is also quite good.
Key Points for Preventing and Controlling Seedling Diseases and Pests in Summer
In summer, temperatures are high and humidity is high, especially in thunderstorm weather after the plum rain season, when seedling diseases and pests are most severe. This is particularly important for plots with relatively high density, poor ventilation, and a high groundwater table, so this period is the key season for preventing and controlling diseases and pests. Below are several recommended methods for preventing and controlling common diseases and pests:
I. Diseases
1. Chinese rose and azalea: powdery mildew and black spot. Once they occur, the plants become short and stunted, not luxuriant, with deformed branch development, unable to bloom, or producing deformed flowers. In severe cases, the leaves shrink and dry up, affecting plant growth and even causing the entire plant to die.
2. Camellia: leaf spot and anthracnose are common diseases that occur from time to time in various places, sometimes very seriously. Affected plants lose ornamental value and cause economic losses.
3. Magnolia denudata: red star disease and leaf spot. When this disease is severe, most of the leaves or the entire leaves become blighted and black, affecting plant growth.
Commonly used chemicals: 70% thiophanate-methyl 600-800 times, 50% carbendazim 500-600 times, 15% triadimefon 2000-2500 times, 62.25% Xiansheng 400-600 times. Spraying for prevention and control in alternating use gives a relatively good effect.
II. Insect pests
1. Scale insects normally harm boxwood, cherry blossoms, camellia, oleander, podocarpus, and so on. Scale insects are the most common pests among flowers. They normally cluster on branches and leaves, and adults and nymphs use specialized mouthparts to suck sap, causing branches and leaves to wither and even the entire plant to die, and can induce sooty mold, causing great harm.
Control chemicals: 20% Jie Shashou 1000-1500 times, 80% emulsifiable concentrate 800-**** times, Longjian 1000-1500 times, Jiebao 1500-2000 times. Spraying is required during the peak hatching period of eggs, and spraying must be uniform and thorough. If the waxy shell has already formed, spraying is unlikely to be effective.
2. Red spider mite is a type of mite. Flowers it normally harms include osmanthus, Chinese juniper, azalea, crabapple, citrus, and so on.
Control chemicals: 20% amitraz 1000-1500 times, 73% propargite emulsifiable concentrate 2000-3000 times, Longjian 1000-1200 times. Alternating use of these chemicals has a certain effect.
A detailed introduction to the occurrence characteristics and prevention and control methods of azalea leaf blight
The azalea is a common herbaceous flower, often used for decoration in home courtyards and gardens, and has attracted many flower lovers to grow it. The cultivation method of azaleas is relatively simple. Everyone knows that a relatively common disease of azaleas is leaf blight. So, do you know how to prevent and control it? Today, the editor will introduce the relevant knowledge to you in detail. Let's learn about it together.
Azalea leaf blight is a fungal disease. The pathogen survives on diseased plant residues and spreads through watering, insects, human activities, and so on. It can occur year-round in indoor environments, and high temperature, dryness, and poor ventilation easily induce the disease. The disease is severe after plants grow weak or suffer insect damage.
Azalea leaf blight mainly harms leaves, mostly occurring at the leaf tips. In the early stage, the lesions are chlorotic yellow spots and spread inward from the edges, appearing irregular. In the later stage, the lesions are yellow-brown, and in severe cases the diseased leaves dry up.
There are three key points for prevention and control: 1. Promptly remove diseased and fallen leaves and burn them in a centralized manner. 2. Strengthen maintenance, frequently spray water on the leaf surface or the surrounding space to improve the micro-environment. Apply more phosphorus and potassium fertilizer to enhance plant growth vigor. 3. In the early stage of the disease, spray 500-800 times dilution of carbendazim or thiophanate-methyl fungicide. If there is damage by insect pests, spray 1000-1500 times dilution of nicotine anabasine for control.
The above is all the content I have learned today about azaleas. I hope flower lovers will find it helpful after reading this article. If you want to learn more about azaleas, please continue to follow Duorou Huapu, and we will provide you with more relevant knowledge!