Control of black spot of oleander
Symptom
The disease spot occurs at the edge or middle of the leaf, semicircular or round. When several disease spots are connected, they are corrugated, both positive and negative, and the front is darker than the back, and the disease spot is grayish white or grayish brown; in the later stage, a black powdery mildew layer is produced in the disease spot, which usually occurs on the overwintering leaves.
Pathogen
The pathogen is fungus, Alternariasp. The conidia are olive-colored, oval, longitudinally and horizontally separated, chain-shaped, and borne on longer conidiophores.
Morbidity regularity
In general, there are many diseases on the old leaves, lower leaves, and tiller strips sprouting in the rhizosphere; spores are transmitted by airflow and Rain Water; during the disease period, such as Rain Water, the disease will be aggravated.
Prevention and cure method
(1) Horticultural control: strengthen management and enhance ventilation and light transmittance of plants. Apply more phosphorus and potassium fertilizer to increase the tree potential.
(2) Drug control: spray 75% chlorothalonil 700 times as much as needed.
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Value and use of oleander
Oleander plant shape is round, leaves such as bamboo like willow, flowers like peach non-peach, beautiful flowers, evergreen four seasons, quite ornamental value. "the cloth leaves are suspicious of bamboo, and the flowers are as tender as peaches; savages never get tired of seeing them, when it comes to tree mash." Thus it can be seen from the ancient poems that oleander has been a popular ornamental flower since ancient times. Oleander has been cultivated in nearly 90 countries and is regarded as a fast-growing tree species because of its fast growth. Algeria also designated it as the national flower. Oleander stems and leaves contain oleander cardiotonic glycosides, which can extract cardiotonic agents, such as diuresis, analgesia, expectorant and asthma.
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Oleander black spot
Symptoms: the disease spot occurs at the edge or middle of the leaf, showing a semicircle or circle, when several disease spots are connected to form a ripple, both sides have, the front is slightly darker than the back, and the disease spot is grayish white or grayish brown. In the later stage, there is a black powdery mildew layer in the disease, which usually occurs on the old leaves. Pathogen and disease status: the pathogen is a fungus of Alternaria (Alternariasp.). The spores are transmitted by wind and rain. Too much Rain Water is easy to cause the disease, and the disease is common on the old leaves, lower leaves and tillering branches germinated in the roots. Prevention and control measures: 1. Strengthen
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