Rhododendron has won the love of many flower admirers and growers with its gorgeous flowers and unique shape. Cheng Yanxiong of the Tang Dynasty said in his poem "Azalea": "It is suspected that it is blood in the mouth, dripping into flowers on branches." A cold night, a few flowers fell to the monk's house. In the poetry of Lang Lang, people listen to the "blood" of the cuckoo bird, and tell the feeling of spring sorrow.
Picture 01~02): "Splendid" azaleas in bloom in the park
In the early stage, Qingjiang Crane also wrote thematic pictures and texts about azaleas. However, at that time, the rhododendrons that bloomed all over the flower beds were called mountain rhododendrons or hairy rhododendrons, which were very "wild".
The rhododendrons on the slope of the recent Fengyuqiao Bridge and Yuehe Square Park are also gradually blooming. People say that the rhododendrons that bloom this time are mostly "brocade rust rhododendrons", which are planted after artificial improvement, and look more elegant and richer than the hairy rhododendrons that opened in the early stage, and have a sense of grace and luxury.
Picture 03~04): Rhododendron blooming on a roadside flower bed
However, in the process of growth and development of rhododendron, the occurrence of root diseases can not be ignored, which can cause "flower fall" and cause the whole rhododendron to die.
In this issue, Qingjiang Crane will continue to pay attention to and chat with all the teachers about the related topics of rhododendron "root diseases". The purpose of this study is to introduce in detail the three major diseases that harm the root system of rhododendron: blight, flower blight and root rot, as well as their pathogenesis characteristics and chemical integrated control methods. I hope you like it and actively participate in the interaction, and forward this issue of pictures and texts.
Picture 05~06): Rhododendron on the slope of the riverbank
Pathogenesis characteristics of rhododendron blight in the field and chemical comprehensive control measures:
Blight is one of the common fungal diseases in the process of rhododendron planting and cultivation, which mainly affects the roots and stem bases of rhododendron aboveground plants, and is mostly seen on cuttings.
In the early stages of the disease, water-stained lesions appear on the affected area (root or base neck), which gradually enlarge and appear dark brown (in fact, the affected area has become brown and rotten). As the disease progresses, the lesions surround the stem for a week, causing the cortex to decay and the xylem to be exposed, and the aboveground parts to gradually wither and die, but "do not fall seedlings".
In view of the prevention and control of rhododendron blight, cultivation management should be strengthened to improve the disease resistance of plants. Dense planting, excessive field humidity, poor drainage, and high groundwater levels are the leading causes of the disease.
Picture 07~08): Rhododendron plants with withered and dead trees
Secondly, in the early stage of the disease, you can choose to spray or water with appropriate fungicides, such as using 50% carbendazim wettable powder 500 times for root irrigation, once every 7-10 days, 2-3 times in a row.
You can also use 500~800 times of 3% methyl allicin aqueous solution, or 80% allicin emulsifiable concentrate 800~1000 times, or 80% allicin chloramphenicol emulsifiable concentrate 800~1000 times, or 25% oxamyl wettable powder 500~600 times, or 70% sodium disulfonate wettable powder 500~800 times liquid spray stems and leaves. It can be used for 7~10 days/time, 2~3 times in a row.
Picture 09~10): Withered and dead trees are related to the root system
Pathogenesis characteristics of rhododendron flower blight in the field and chemical comprehensive control measures:
Rhododendron blight is also known as "root blight". It mainly affects the leaves, flowers and shoots of rhododendrons, and in severe cases, it can also affect the root system of rhododendrons.
At the beginning of the disease, small brown "water-stained" spots appear on the leaves, which begin at the leaf edge and gradually expand and appear in the shape of a whorle. The lesions are greenish and grayish-brown, the junction between the sick and the healthy is wavy, and the back of the leaves is covered with a white mold layer. After the flowers are damaged, brown lesions appear, which affects the ornamental value. When the disease is severe, the root system will also be infected and gradually turn black and rot, resulting in poor growth of rhododendron aboveground plants, loss of water and yellowing.
When the damage is severe, the rhododendron "withered" and "falls leaves", and the whole plant withers and dies.
Picture 11~12): the central diseased plant in the flowering cluster
To prevent and control flower blight (caused by Phytophthora fungus), we must first keep the plants ventilated and light-transmitting, and reduce the breeding environment for germs. The severity of the disease is related to the influence of rainfall, precipitation, air humidity and other factors.
Usually when the rainy season comes, the disease is basically the case, and as the rainfall increases, the disease becomes epidemic.
Secondly, fungicides with systemic effect can be used for prevention and control, such as using 75% chlorothalonil wettable powder 800 times liquid for spray treatment, once every 5-7 days, 3-4 times in a row.
Image 13~14): Rhododendron in the morning light
You can also use 800~1000 times of 50% carbendazim downy mildew carb wettable powder, or 600~800 times of 70% fluopyramide downy mildew carb hydrochloride suspension, or 800~1000 times of 35% fludioxazil essence methalene wettable powder, or 80% 800~1200 times of 80% fine methaloxamine aqueous solution, or 1500~2000 times of 20% cyanogluzole frost urea cyanogen water emulsion.
Pathogenesis characteristics of rhododendron root rot in the field and chemical comprehensive control measures:
Root rot is one of the most serious diseases of rhododendrons, mainly affecting the roots and root necks of plants. The pathogen is the oomycete spores of Phytophthora cryptophylla, which invade the rhododendron plant from the young roots or wounds by rainwater after overwintering on the diseased part or diseased residue. Rhododendron plants with "fungus" at their root necks often become more and more severe.
Picture 15~16): Rhododendron artificially and professionally grown
At the beginning of the disease, water-stained lesions appear on the roots, which gradually expand and rot brown. With the development of the disease, the aboveground leaves gradually turn yellow and fall off, and the whole plant withers and dies. Dead rhododendron plants often have "black cords" on the root surface.
For the prevention and control of root rot, it is first necessary to choose a slightly acidic soil with good drainage for cultivation to avoid water accumulation.
Picture 17~18): Rhododendron in the park
Secondly, in the early stage of the disease, a broad-spectrum fungicide can be used for root irrigation, such as using 1000 times of 50% methyl tobuzin wettable powder for irrigation, once every 10 days or so, 2-3 times in a row.
You can also spray 1500~2000 times of 10% cyanogluconazole suspension, or 500~600 times of 5% cyanogluconazole suspension suspension, or 1500~2000 times of 52.5% oxazoleone cream urea cyanide dispersible granules, or 800~1200 times of 30.25% methyl syringylmystrobin frost urea cyanide wettable powder, or 800~1000 times of 50% fluopyramide zhongshengmycin wettable powder, or 800~1000 times of 69% enoylmorpholinogencozeb wettable powder1000 times liquid spray stems and leaves can be treated.
Picture 19~20): Rhododendron planted in a roadside flower bed
In addition, it can also be combined with soil disinfection, increase organic fertilizer and other measures to improve soil fertility and enhance the disease resistance of plants.
Words written at the end:
In summary, the prevention and control of rhododendron root diseases requires comprehensive consideration of a variety of factors, including cultivation management, disease identification, and chemical control. Only by taking scientific and effective measures can we ensure the healthy growth and beautiful bloom of rhododendrons.
Picture 21~22): Rhododendron in full bloom
Attached is an article on azalea planting in the early stage of Qingjiang Crane:
01) The azalea, which enjoys the reputation of "Blooming in the West", is planted "skillfully", and the flowers are stunning and charming
02) What are the methods of rhododendron propagation and seedling raising, and the seedlings become seedlings and bloom early?
03) Rhododendron "5 diseases" and "crazy work", teach you a "dose", precise prevention and control medicine to eliminate the disease
Picture 23~24): Rhododendron under a shade tree