Browning of rhododendron leavesis a common symptom. It may result from errors in the care of these plants, but also indicates a dangerous disease attacking rhododendrons. And then we must intervene very quickly if we want to save the plants. See where thebrown spots on rhododendron leavescome from and how to treat them. Here are the5 Top Causes Of Rhododendron Leaves Browning!
Browning of rhododendron leaves
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1. Browning of rhododendron leaves due to inadequate fertilization
Rhododendrons need a lot of nutrients. Their deficiencies are quickly revealedin the form of discoloration on the leavesThe effects of the deficiency of individual elements are often mistaken for symptoms of diseases or frostbite, so it is worth finding out how to identify them.
Whenon the edges of the rhododendron leaves, brown spots appear , and yellowing of the tissues between the veins, this is a symptom of potassium (K) deficiency.
Brown-red spots on the edges of rhododendron leavesmay be the reason for a lack of boron (B).
Browning of the rhododendron leavesmay also indicate a deficiency of phosphorus (P) in the plant.
To ensure the availability of the missing elements for plants, it is worth taking care of the acidic reaction of the soil required by rhododendrons (pH 4.5-6.0) and using fertilizer mixtures designed specifically for azaleas and rhododendrons.If the soil pH rises to too high values, acidifying fertilizers are used. Mulching the soil under the rhododendrons with acid pine bark also helps.
2. Rhododendron leaf spot
Rhododendrons suffer from leaf spot very often. This disease is caused by different species of fungi. The development of the disease is gradual. Initiallybrown spots appear at the edges of the rhododendron leavesand then spread over the entire surface of the leaf blade. The spots may blend into one or be scattered over the entire leaf surface.
TaRhododendron leaf diseaseis easily controlled with Topsin M 500 SC. To prepare the spray, dissolve 1 ml of Topsin in 1 liter of water. Spraying should be repeated after 14 days. Alternately with Topsin or preventively after the bush has healed, rhododendrons should be sprayed with the natural strengthening agent Biosept Active. In order to prevent recurrence of infections, it is necessary to cultivate rhododendrons in the most favorable soil and light conditions for them, as well as ensure their proper fertilization.Leaf blotch fungi primarily attack weakened shrubs.
3. Browning of rhododendrons caused by phytophthorosis
Symptoms of phytophthora appear on shoot tips in rhododendronsand other members of the heather family (Ericaceae). This disease develops with an excess of moisture in the soil. Initially, the petioles turn brown from the base. Then the brown discoloration spreads to the entire leaf blade. Sometimesbrown spots appear in different places on the rhododendron leavesand gradually increase in size. Brown spots are also visible on the branches. The symptoms gradually spread downwards until the entire bush dies off over time.
A characteristic symptom of phytophthora isthe fall of browning leaves, even with a slight movement of the branchOn the fallen leaves, in high air humidity, within a few days, clearly visible sporulation of the fungus develops.After pulling the bush out of the ground, a strongly reduced root system and rot at the base of the shoot can be observed.
Plants infected by the disease should be dug up together with a lump of soil and burned. Disinfect the area after the removed plants with a soil and water solution of potassium garden soap (4 l of liquid per 1 m²). Cover the disinfected soil with foil for a few days. After planting new bushes, water them prophylactically with Polyversum WP (100 ml of liquid per 1 bush - the treatment should be performed 3 times at 21 days intervals). After 2-3 weeks, spray the plants, both newly planted and those growing in the vicinity of the infection site, with Biosep Active (5-10 ml dissolved in 10 l of water).
4. Browning of rhododendrons due to water shortage
Proper development of rhododendrons depends on adequate hydration. The greatest demand for water for shrubs occurs during the period of growth and flowering. In hot summer weather, additional irrigation is sometimes needed.The signal for watering the shrubs islongitudinal curl of the leavesIn this way, the plants protect themselves against excessive water loss.
Suchleaf curl often occurs also in winter , when evergreen rhododendrons constantly transpire water, unable to replenish it from the frozen ground. To prevent this from happening, water the evergreen rhododendrons abundantly in late autumn and, if necessary, also in winter during the thaw.
5. Browning of rhododendrons caused by freezing
Rhododendrons are frost-resistant plants. However, in non-wintering leaves of azaleas and rhododendrons, in extremely harsh winters with large temperature fluctuations, there may be enough damage to the leaves and one-year-old shoots.A symptom of freezing of shoots is browning of leaves, which starts at the tops and spreads along the edges of the leaf bladeTo protect rhododendrons for the winter, especially young and freshly planted shrubs, cover them with straw or agrotextile and mound them with a thick layer litter.
The protection agents and fertilizers listed in the article are usefulin the care of rhododendrons and combating leaf diseasesyou can order in our store. We guarantee high quality products, low price and fast shipping. To see the available preparations, press the button below.
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MSc Eng. Agnieszka Lach
