Rhododendron rot
Symptoms of rhododendron rot only harm flowers, resulting in shortened florescence, flower sagging, early withering and shedding. After the petals are infected, the diseased part loses its luster, is waterlogged, softens and fades, and finally turns brown, rotten and black, and a gray mildew layer grows on the surface when it is wet, affecting the ornamental.
The pathogen and incidence regularity of the disease belongs to semi-known bacteria subfilaria fungi. The bacteria form sclerotia on the rotten flowers, and the sclerotia fall into the soil with the abortive flowers to overwinter. During the flowering period of the following year, conidia are produced, which spread with the wind and rain or air flow, invade the host tissue when the flowers sprout and form disease spots, which are generally serious in the spring rain season. The symptoms of the disease are dirty white to brown spots on the petals of red varieties and light brown spots on the petals of white varieties. In the later stage, black irregular flattened sclerotia were produced on rotten flowers. Fall into the soil with the flowers to survive the winter.
Prevention and cure method
1. After the rhododendron flower fade, the diseased and residual plants, flowers, fallen leaves and concentrated burning should be dealt with in time to reduce the source of infection.
2. Use 50% benzoate wettable powder and 50 parts of plant ash to spread evenly on the topsoil of flower beds and flowerpots. From early spring before flowering, 1000 to 1500 times methyl topiramate is sprayed 1 to 3 times every 7 to 10 days to control the disease.
3. Spray 12x to 160x Bordeaux solution or 50% Dysenamine 800 to 1000 times when you get sick.
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Control of Root Rot of Rhododendron
Root rot is a serious threat to rhododendron. Although its incidence is not high, the mortality rate after infection is very high. Therefore, attention must be paid to the prevention and control of root rot in the cultivation and management of rhododendron. Root rot is a soil-borne disease caused by Fusarium oxysporum, which mostly occurs in the roots of rhododendron, because these parts are often moist, lack of sunlight, and Fusarium oxysporum fungi are active frequently. Once it invades the cortex, it will soon cause rot, watery brown spots and soft rot will appear on the roots, and the xylem will be black and brown.
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Control of Tetranychus Tetranychus in rhododendron holly
Distribution and harm have occurred in Japan, South Korea, the United States and other countries. Harm to azaleas, camellia, tea, etc. Morphological characteristics of female mite: reddish brown, body length about 0.14 mm. Male mite: body length is about 0.33 mm. The damage of this mite to rhododendron is mainly from May to July and from October to December, and it can absorb juice on the front and back of the leaves, and the leaves are yellowish green in severe cases.
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