Rhododendron is a popular spring flowering shrub that has shiny and leathery leaves. There are many species of rhododendrons and some tend to have a few different features like some which have scales and hair on the foliage underside. The rhododendron produces clusters of bell shaped flowers that are very attractive and make the rhododendron plants good for landscaping. These attractive rhododendron flowers appear in different colors like. white, pink, yellow, purple and peach. This beautiful plant is prone to many diseases that can cause a lot of damage if not well handled.
These rhododendron diseases are caused by the fungi that belongs to the phytophthora genus especially the Phytophthora cinnamonia fungi that causes root rot. Root rot is prevalent in areas where there are moist and warm soil temperatures. The symptoms of the root rot tend to vary with the mode of cultivation. However, the main symptoms are. reddish brown discoloration that advances to the larger roots and the lower part of the main stem. Root rot can be avoided by planting the rhododendron in well drained areas and planting them in the same soil level as the one in the soil nursery.
The Phytophthora cactorum causes dieback of the stem. This disease does well in the hot wet climate and it is characterized by brown spots on the foliage and the stem and drying of the leaves before they fall off. Dieback can be prevented by destroying all the infected plants, avoiding watering in the afternoon, spraying the plants with protective fungicides and providing enough space between the plants for good air circulation.
Blight rhododendron diseases mostly attack the petals and the twigs. The petal blight affects the flowers and is characterized by the symptoms like. tiny pale colored spots on the petals that enlarge quickly and the petals become soft and watery. When the disease advances, the entire flower rots. Petal blight is controlled by applying fungicides on the soil for about two to three weeks and the affected petals should be isolated from the rest of the garden and destroyed.
Twig blight attacks large branches of old plants. The infected twigs wilt and the leaves die while the barks of the affected twigs turn reddish brown. Twig blight is controlled by pruning the affected twigs and destroying them.
The leaf gall rhododendron diseases are caused by a fungus that attack mainly during early spring. Leaf gall is characterized by the thickening of the shoot before it turns fleshy and pale. During the advanced stages, the leaf galls are covered by some white powdery substance. It can be controlled by isolating and destroying the affected leaves.
Rhododendron diseases can be controlled by maintain the good and recommended soil requirements that favor the plant, regular watering especially during growth and dry seasons, proper mulching to prevent drying of the roots, enough fertilization during spring and proper pruning to enhance good air circulation.
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