Why do the leaves of rhododendron turn yellow and what to do for treatment
The most beautiful, profusely flowering rhododendrons are engraved in the memory of everyone who has ever seen them for a long time. But often all the leaves of your favorite rhododendrons turn yellow. Responsible gardeners need to be clear about the causes and remedies for this problem. Only in this case the plants will actively develop and will be able to please the owners for many years without any problems.
Causes of yellowing
Many factors affect plant health. Therefore, the reasons for the yellowing of foliage in rhododendrons are different.
Non-compliance with watering rules
Rhododendron is a moisture-loving plant. Therefore, with irregular and insufficient watering, especially in the hot season, the leaves become lethargic, quickly turn yellow and partially fall off. It is necessary not to pour the rhododendron, otherwise the root can simply rot. Yellow foliage is also observed with stagnant water.
Lighting
Rhododendrons, especially those found in the southern regions, suffer from intense solar radiation in summer. Leaves are the first to signal the problem - they turn yellow and dry out. They are shaded using shade nets, dense agrofibre or sheets of colored polycarbonate. Rhododendrons grow best in partial shade.
Wrong ground
Rhododendron belongs to the extensive Heather family, and requires acidic soil to grow them. Only then will the plant be able to assimilate nutrients from the soil. Usually, the soil for the Heathers consists of sour high-moor peat and rotted coniferous litter. To maintain the required acidity level, the soil is regularly acidified. Citric acid, colloidal sulfur, electrolyte are used.
Damage to the root system
The root system of rhododendron is fibrous, located in the upper layer of the soil. It is sensitive to damage and does not differ in growth vigor. During agrotechnical measures (loosening, weeding), it is easy to damage it. This will cause the foliage to turn yellow. Overheating the soil during the hot summer months will also cause the foliage to change color.
The way out is to shade plants or plant large trees in the diffused shade. A good option would be to land under conifers. Will help save the root system from overheating and excessive evaporation of moisture by mulching the soil. Sour (high moor) peat, moss, coniferous sawdust and pine needles are suitable.
Pests
Pests bring many problems to cultivated plants, unfortunately, rhododendrons are no exception. And often, pest damage is one of the reasons for yellowing of leaves.
Rhododendron bug
When affected by this pest, the leaves lose their usual color and become light, pale, and later acquire a yellowish tint. With severe damage, the leaves curl and then fall off. On the underside of the leaf, sticky traces of insect excrement are visible. For the fight, insecticides BI-58, Karbofos are used. Moreover, several treatments should be carried out.
Mealybug
This pest actively reproduces in warm and dry conditions, high humidity prevents its reproduction. The mealybug resembles small lumps of cotton wool. They attach to the surface of leaves and settle in their internodes.
It is important to try to mechanically clean all the affected parts from the worm before chemical treatment of the plant. Use cotton swabs and soapy water. And only then it is worth spraying with a systemic insecticide; fit Aktara, Confidor.
Aphid
When affected by such a common pest as aphids, the leaves of rhododendrons gradually brighten and acquire a yellowish tint. Aphids usually settle on the underside of the leaf. Control measures - spraying with insecticides - Aktellik, Nurel D, Confidor.
Black thrips
When thrips are affected, the upper surface of the leaves is covered with grayish holes, the bottom - black holes. The affected areas turn gray, then turn yellow and fall off en masse. Control measures - spraying with an insecticide solution
Khrushch
The root system can also be damaged by such a dangerous pest as the larva of the May beetle (Khrushch). This leads to yellowing and leaf fall. With severe damage, even the shoots dry out.
Diseases
Rhododendrons are often affected by various diseases, and often this is the cause of yellowing, as well as leaf fall.
Septoria
It is the most dangerous fungal disease of rhododendrons. With septoria, small red spots appear on the leaves, which quickly increase in size and brighten. Then the foliage turns yellow, dries up and falls off. Without timely assistance, a rhododendron can be left completely without foliage. Fighting it - removing the diseased part of the bush, as well as treating it with fungicides, for example, Ridomil Gold is often used.
Chlorosis
In many plants, including rhododendrons, non-infectious chlorosis is the cause of yellow foliage. This is especially evident in the spring, at the beginning of the season. Chlorosis occurs when there is a deficiency of nitrogen and iron in the soil. With chlorosis, the foliage becomes light, yellowish or covered with spots of a characteristic shade.
Fusarium
A dangerous fungal disease of the root system. When affected by rot, the leaves first turn yellow and dry, then the shoots dry out.
Requires quick treatment, with the use of fungicides, otherwise the plant will quickly die.
What is this process
The yellowing of leaves in rhododendrons (azaleas) can occur both due to natural biological causes and as a result of improper agricultural technology. It is especially dangerous if the discoloration of the leaves is accompanied by the appearance of various spots. This will most likely be the onset of disease or pest damage.
If turned yellow in autumn
Color change by autumn is a completely natural process. Depending on the cultivar, the foliage of rhododendrons becomes yellowish, brown or red. In this case, the gardener does not need to worry, but needs to be sanitized by removing all dried leaves and twigs.
If the stem is yellowing
If the stem of a rhododendron began to turn yellow, then, in most cases, you need to pay attention to the plant nutrition scheme. It is advisable to use special fertilizers for Heathers; in addition to top dressing, they also acidify the soil.
Prevention
For prevention, it is necessary to carry out systematic spraying, as well as spilling with drugs for diseases and pests. It is necessary to monitor the frequency of watering, at the same time to avoid overflows.
And, of course, maintaining the right soil acidity, as well as shading during the hot summer months, will help keep foliage healthy and green.
