Rhododendrons can be affected by a condition called "physiological leaf spot." Can you help me with my rhododendron? There are several diseases that could cause black spots on your rhododendron, but one of the most common is Cercospora leaf spot. While it may be ugly, this common rhododendron disease is more superficial than serious. Prolonged saturation leads to diseases that kill an entire plant, not just its leaves. Troubleshoot your rhododendron by taking a small cutting to a local Master Gardener for a diagnosis. Look for yellow leaves, scorched brown spots, powder or discoloration. Most gardeners, whether new to the art or seasoned growers, have come across powdery mildew on plants. They range from light green to a purplish or reddish color. A rhododendron has a showier canopy with 10 or more stamens, while azaleas have five stamens per lobe. * Mites – The tiny mites that invade the leaves of an azalea or rhododendron are often hard to catch before they create a serious problem for the plant. 2 Aug, 2009 Naima Manal's articles on health, diet, nutrition, alternative medicine, education, parenting, crafts, travel, home and garden and home improvement have appeared on various websites. Prune both plants after the bloom period to assist in next year’s big production of brilliant blooms. Fungal dieback attacks new leaves first, causing brown spots Fungal dieback then spreads to older foliage, causing spotting The leaves attacked wither, die and drop The more you know about the type of plant you have, the more you may be able to easily identify the type of issue from which it is suffering. The genus Rhododendron now includes the azalea, which was reclassified to fall under this genus. This kind of damage is most likely due to unfavorable environmental and weather conditions. The canopy of the rhododendron can look healthy and full and the buds big and bulbous, but you can still have a fungus lurking within the plant. in Journalism from the University of Nevada, Las Vegas. During Summer, it is recommended that you check plants under eaves where rainfall may not penetrate even on the wettest days. Many leaves on my rhododendron have turned brown. There are a few things to do to keep rhododendron diseases from occurring in your green spaces. There are several diseases that could cause the symptoms you are seeing on your rhododendron. Brown spots on rhododendron leaves may not be a sign of disease. The symptoms of azalea leaf gall are varying sizes of sores on the leaves. Any brown leaves will drop off as the new growth emerges. You can also use products that contain imidacloprid or dinotefuran to spread around the soil to keep creepy crawlers from making purchase in the soil or climbing up the lower branches of the hardy rhododendron or azalea. These common deficiencies may cause leaf spots: Calcium. Learn which plants thrive in your Hardiness Zone with our new interactive map! Remedy: Avoid overhead watering. The former is a naturally occurring phenomenon that takes place as the result of changing weather patterns and doesn't necessarily indicate a dead plant. Now the leaves are turning a rust color, curling upward, and falling off. There are various other rhododendron diseases, like leaf spots, and root and crown rot. Rhododendrons grow best in soil that is consistently moist but never soggy. This windborne spore reinfects only rhododendron. Petal blight will appear as white to brown spots that quickly take over the petals of the rhododendron or azalea blooms. This spring’s bloom was the best in a long time. This looks like the typical damage done by one of the fungal leaf diseases of Rhododendron. Brown spots on Azalea leaves are commonly caused by a … What causes it? Previous. If they cling to surrounding leaves as they die off, then they are spreading the fungus. Brown edges to leaves, called "marginal leaf necrosis" (this simply means that the edge of the leaf has died), may be fairly narrow with a lot of green leaf remaining in the middle. This pesky insect lays its eggs on the developing flower buds and moves on to surrounding plants. Each is prone to the same types of leaf problems. A shortage of this vital element results in the withering of new growth, curled tips, and yellow or brown leaf spots. These show up on older, mature vegetation near the bottom of the plant. Red leaves could be a sign of a light problem, watering problem or soil chemistry. Fungi from the Phytophthora, Cercospora, Colletotrichum, Pestalotiopsis and other genera are known to cause brown spots on the leaves of rhododendrons. When it comes to incorporating large, full-bodied flowering shrubs for privacy and delineation of spaces in a landscape, one popular choice is the rhododendron. To control the damage that can be done to rhododendron leaves by the insects that immigrate to your garden, you need to control the population of these pesky invaders. © Copyright 2020 Hearst Communications, Inc. Purchase plants from a reputable nursery to ensure they are disease free. Azaleas and rhododendrons like to have a layer of mulch to protect the shallow roots of the plants. Some ... Rhododendron leaf-miner (Fig. There are several types of fungus that can cause this. Check the underside of the plant’s leaves on a regular basis. The peak season for rhododendrons is early spring and late May. Petals feel slimy when rubbed between fingers. Properly dispose of the infected plant parts far away from rhododendron shrub. So it's natural to want the bushes to look attractive year-round. All Rights Reserved. This condition is caused by poor root health, improper irrigation as in over- or under-watering, drought and extreme heat exposure. The most common types for gardeners include: If you are considering planting rhododendrons or have inherited a garden populated with these healthy evergreens, then you may want to understand its origins. Always seem to have a layer of mulch to protect the shallow roots of plant... Occurring in your rhododendrons in a location where they receive good sunlight rhododendrons! Could happen due to unfavorable environmental and weather conditions proper planting and care water! Mild and wet weather in the garden the blooms to begin on your.... Family and are sometimes affected with brown spots and understanding how to prevent wetting of the infected parts! 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