Do Camellia Bushes Lose Their Leaves in Cold? Leaf spots are most prevalent after periods of cool, wet spring weather. Some have red-brown borders with silvery gray centers. Generally, rhododendron bush blooms are larger than azaleas, and they bloom later in the spring. Leaf and flower gall Exobasidium vaccinii = Exobasidium azaleae. Leaf Spots. Traditionally, botanists used to count the stamens when a plant was blooming, classifying those with 10 stamens as rhododendrons and those with five stamens as azaleas. They would probably also give some control of rhododendron leaf spots (Provanto Fungus Fighter Plus and Toprose Fungus Control and Protect mention 'leaf spot of ornamentals' on the label). A second type of Rhododendron issue is brown spots on the leaves. Fungal Disease Powdery Mildew . From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. Feed rhododendron only once a year, when buds swell in the spring. Most garden centers carry organic fungicides as well as conventional ones, so you’ll be able to find a product that meets with your gardening philosophy. Andrew. Rhododendron Leaf Spot. Troubleshoot your rhododendron by taking a small cutting to a local Master Gardener for a diagnosis. Rhododendron tip midge – New growth distorted, leaf margin curled under tightly; small (1.3-mm) maggots inside cavity formed by curled margin. Late spring and early fall are the best seasons for planting or transplanting rhododendron. If the problem is severe or persistent, consider replacing the rhododendron with a more desirable variety. Pruning is not necessary to build a good structure for the plant, but you can and should deadhead flowers as they die. Rhododendron leaves are large, lush and green. The leaves are spirally arranged; leaf size can range from 1–2 cm (0.4–0.8 in) to over 50 cm (20 in), exceptionally 100 cm (40 in) in R. sinogrande. Red berries grow on sleek green leaves to increase the aesthetic appeal of this bushy shrub. Another cultivar, 'Virginia Richards,' gets brownish purple spots on both tops and bottoms of leaves. This happens just before winter or in summer drought. Insect problems include aphids, borers, lacebugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips and whitefly. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. These spots may feel bumpy on the surface due to the presence of fungal structures. Several fungi cause leafspotting on rhododendron leaves, often as a secondary effect of the shrub being in poor condition from some other cause. This windborne spore reinfects only rhododendron. Leaf and flower gall Exobasidium vaccinii = Exobasidium azaleae. Rhododendrons and azaleas are some of the most popular spring-flowering shrubs in the landscape, and healthy plants can give years of pleasure. Santa Cruz, a law degree from U.C. Thank you for asking about your Rhododendron leaves. They are termed "queens of the shade garden" because they usually do not like full sun, preferring dappled or deep shade in most cases. It is a list of products currently available to the home gardener. Unstressed rhodies usually do not get attacked by fungal diseases, so keeping the shrubs happy is a good way to keep them healthy. Powdery mildew on rhododendrons is a fungal infection of the leaves. … There is no cure for the necrotic ring spot virus, but you can control the disease by properly watering, fertilizing and pruning infected rhododendrons to keep the shrubs strong and healthy. It is uncommon to see necrosis occur out to the leaf tip. Rhododendron lace bug – Chlorotic spots on upper leaf surface, numerous dark spots of insect excrement on lower leaf surface; small, dark, spiny insects and slightly larger (3-mm), lacy insects on lower leaf surface. Foliage often remains attractive through winter in warmer zones. There are various other rhododendron diseases, like leaf spots, and root and crown rot. They have proven to be valuable garden mainstays in the spring thanks to their spectacular clusters of showy blooms. Wilting, browning at the edges, brown spots in the center of the leaf or very dark green veins are all signs of different problems. My Encore Azalea Is Turning Brown in the Winter, When to Fertilize Magnolias and Camellias, The Old Farmer's Almanac: Growing Rhododendrons, Gardening Know How: Issues with Rhododendrons: Dealing With Rhododendron Insect Problems And Diseases, Clemson Cooperative Extension: Azalea & Rhododendron Diseases, Cooperative Extension: Rhododendrons with Brown Leaves. It’s a firm favourite with wildlife – pollinators and birds are drawn to this variety as it offers food and shelter. Inclusion of a product does not indicate a recommendation or endorsement by the RHS. Leaf spots caused by various fungi may be seen on rhododendrons and azaleas. A rhododendron (Rhobodendron spp.) Rhododendrons are lovely plants with enchanting blooms that range from dark red to lavender. For instance, the rhododendron cultivar 'Unique' shows almost no upper leaf change other than occasional very faint lighter yellowish areas, while the underside of the leaves is completely covered in brown spots. Common insect pests on rhododendrons and azaleas include: Lace bug: If you notice leaves that look diseased, always look at the under side. Determining the underlying problem is necessary to restore the rhododendron's health. Some have red-brown borders with silvery gray centers. The spot's upper surface may feel bumpy due to the fungal fruiting bodies (pycnidia). 'Nova Zembla' is one of the iron-clad rhododendrons, an informal name that indicates rhododendrons that are easy to grow and are hardy, even in cold climates. Management Recommendations. One should remove leaves that have fallen, and take care when watering to keep the leaves … In addition there are many different fungi that have been found less frequently in association with leaf spots on rhododendron in the PNW. Before you begin, make sure that what you are seeing is not just leaf senescence – old leaves falling off at the end of their two or three year life. Recognition and Life Cycle Adults are about 1/8-inch long. In warm areas, they require afternoon shade, and in cool or temperate zones (to zone 6), the shrubs do best with six hours or more of direct sun each day. Control rhododendron leaf spot, with the advice from our guide. Keep deadheading. This is caused by various species of the fungus Exobasidium. 8). Rhododendron (Rhododendron) Plant Health Problems Diseases caused by Fungi: Leaf spots. Glomerella canker and dieback Glomerella cingulata Colletotrichum gloeosporioides [anamorph] Gray blight Pestalotia sydowiana. Even experts can have difficulty distinguishing between the two in some cases. For the purpose of care and disease prevention, the distinction is irrelevant since both types of rhododendrons have the same care requirements and are susceptible to the same diseases, and given the genus, it is perfectly correct to call either one "rhododendron.". The diseases caused are usually minor, … Brown spot often occurs in rainy season and humid weather. Figure 2. Repeat the treatment every two weeks until the disease is under control. Control mainly consists of picking off the galls and disposing of them. Very small black dots (fruiting structures of They often infect through wounds. Rhododendron Lace Bug (Stephanitis takeyai) Lace bug damage is indicated by stippling (very tiny spots) on leaves of plants growing on dry sites and those with low plant diversity. Rhododendron Leaf Spot. The body is pale yellow. One of the reasons gardeners love rhododendrons is that they are fairly low-maintenance plants and remain healthy unless stressed. Signs of rhododendron distress can usually be traced to incorrect culture or siting. Management. Symptoms First, light-yellow or yellow-green spots on the upper leaf surface and brown to purple spots on the lower surface. Its flowers are bright red with darker spots that may fade to deep pink in bright sun and are up to 5 in. Several fungi cause leaf spots on rhododendron. This condition is caused by several different species of phytophthora fungi, and each creates slightly varying symptoms. Powdery mildew on rhododendrons is a fungal infection of the leaves. Do not forget to review your cultural practices in order to prevent the issues from happening again in the future. Leaf gall is a common springtime Rhododendron disease, but it is not particularly serious. This condition is caused by poor root health, improper irrigation as in over- or under-watering, drought and extreme heat exposure. Enjoy towering lilies with gigantic, scented blooms. I will try to provide a picture 2) How should I treat it? 1) Does it sound like rust? Rhododendron is a genus of shrubs and small to (rarely) large trees, the smallest species growing to 10–100 cm (4–40 in) tall, and the largest, R. protistum var. Unfortunately, the lovely plant is prone to disease and pests. is called the queen of the shade garden since these flowering shrubs not only tolerate some shade but crave it. Sometimes infected leaves become covered with white spots. Small, black fruiting bodies may be visible on the upper or lower surfaces of the spots (Figure 3). Spots on rhododendron leaves. Several fungi cause leaf spots on rhododendron. However, azalea varieties tolerate both chill and heat better than rhododendron bushes. Epsom Salts* According to the American Rhododendron Society, if the plant has older leaves that have turned yellow between green veins, you likely have a Magnesium deficiency.Sprinkle some Epsom Salts* around the plant to correct the issue.. Iron Sulfate*. It is an upright shrub growing 5 to 8 ft. tall and 5 to 6 ft. wide. Phyllosticta leaf blotch is caused by several Phyllosticta species.. Be sure to sterilize the pruner before and after each use to avoid spreading the disease. The body is pale yellow. Chlorotic (a yellowing of the leaves) azaleas and rhododendron are a common sight in the Indiana landscape. The most common fungal leaf spot pathogens of Rhododendron spp. plants affected by it have leaves, buds, or stems that develop swollen, distorted growths in April or May. The plants are able to survive and bloom for many years. Fungal diseases usually only attack plants that are stressed by an injury or by poor environmental conditions. As many as ten different leaf spot fungi can be found on rhododendron. Florida Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org . Both adults and nymphs feed on the backside of the leaf resulting in formation of yellow spots. What causes it? On rhododendrons, the disease often fails to develop the distinctive powdery white … The showy flowers can be white, pink, purple, yellow or red. Rhododendron Leaf Spot When Rhododendron occurs, there will be small brown spots on the leaf surface, which will gradually form irregular large spots, and then the leaves will fall off, affecting the flowering of the year and the development of flower buds in the next year. Every gardener with a shady corner loves rhodies. The lacy wings (very distinctive) are held flat over the back and are transparent with two dark spots present. The term chlorosis gets its name from the lack of chlorophyll, the pigment responsible for healthy plants’ green color. In tropical regions, rhodies do best in full shade. Exobasidium leaf spot Exobasidium burtii. Several fungi cause leafspotting on rhododendron leaves, often as a secondary effect of the shrub being in poor condition from some other cause. Recognition and Life Cycle Adults are about 1/8-inch long. Thanks! Dig a hole in the soil as deep as the plant's root ball but twice as wide. She currently divides her life between San Francisco and southwestern France. Rhododendron-Ramorum Leaf Blight and Shoot Dieback. The lacy wings (very distinctive) are held flat over the back and are transparent with two dark spots present. Was out walking at the weekend and lots of rhododendrons with what I think is leaf spot caused by a fungus. Leaves are the best indicators of plant problems. Infected leaves can become dwarfed and distorted, but the virus rarely causes any serious damage to rhododendron shrubs. Photo by Jennifer Parke, 2003. RHODODENDRON811 Leaf Spot.—The leaves, particularly on weak plants, are occasionally disfigured by dead spots, which are usually light-colored with a dark »a Yoy further information on rhododendron diseases see: White, R. P., and C. C. Hamilton. This disease, caused by the fungus Glomerella cingulata, results in rounded spots on the leaves. Leaf spots are most prevalent after periods of cool, wet spring weather. The most common hosts of Phyllosticta leaf blotch include witchhazel (Hamamaelis), hydrangea (Hydrangea), rhododendron/azalea (Rhododendron), holly/inkberry (Ilex), mountain laurel (Kalmia) and andromeda (Pieris). Generally, rhododendrons thrive in U.S. Department of Agriculture plant hardiness zones 4 through 9. A fungal attack causes an outbreak of spots on the leaves. Throughout the year, fungal spots (Cercospora species, Septoria species, Phyllosticta species and Colletotrichum species) of various colors appear on azalea and rhododendron leaves. Photo by Everett Hansen. It is uncommon to see necrosis occur out to the leaf tip. In the past week or two, the leaves have gone from a dark waxy green, to a mottled, dark … If you notice signs of a fungal infection, prune away the infected areas after sterilizing all equipment and apply fungicides. This unsightly fungus is referred to as Cercospora leaf spot (Cercospora handelii). Various fungi cause branch and twig dieback, collar, root and crown rot and leaf spot diseases on rhododendron plants. Avoid frequent overhead irrigation, remove fallen leaves, and keep leaves dry when watering plants. Rhododendrons and azaleas are both in the Rhododendron genus, and it can be hard to tell them apart. The eye-catching and exotic lily-like flowers of these alstroemeria will be the stars of your summer displays, giving months of vibrant colour from June to October. Azaleas and rhododendrons are members of the plant family Ericaceae and the genus Rhododendron. What causes it? 8). Some plants are grown for foliage, and others are grown for flowers. When Rhododendron occurs, there will be small brown spots on the leaf surface, which will gradually form irregular large spots, and then the leaves will fall off, affecting the flowering of the year and the development of flower buds in the next year. Necrotic ring spot is a virus that causes light-colored spots or streaks on the rhododendrons leaves. Best way to treat rust on a rhododendron? Unfortunately, the lovely plant is prone to disease and pests. Although unsightly, they rarely cause serious injury. They need water and humidity even in the summer. Also, take care to not use too much fertilizer. Azalea leaves may be slightly more narrow and pointed than rhododendron bush leaves. The plants are able to survive and bloom for many years. Cercospora leaf spot is most troublesome in late summer and fall, or whenever periods of warm temperatures and high humidity or leaf wetness occur. Rhododendron flowers and buds are attacked by the Botrytis cinerea fungus, and leaf gall fungi, powdery mildew and different types of rusts affect rhododendron leaves. The symptoms usually include discrete spots with tan … Insects, Diseases, and Other Plant Problems: Rhododendrons are susceptible to insect and disease problems. 15/52 Spots. Photo by Jennifer Parke, 2003. Leaf spot disease can develop if grown in deep shade or suffers drought stress. Leaf spots can be caused by powdery mildew or rust, or a number of other common pathogens. My rhododendron has leaves that are turning yellow, and some have spots that resemble even coalesce over the entire leaf. Here is some of the information from the PNW Plant Disease Management Handbook about Physiological leaf spot: "Cause Phyllosticta spp., a fungus found on wild as well as cultivated rhododendron. Promptly remove and destroy all infected leaves, both on the plant and on the ground. Control rhododendron leaf spot, with the advice from our guide. They would probably also give some control of rhododendron leaf spots (Provanto Fungus Fighter Plus and Toprose Fungus Control and Protect mention 'leaf spot of ornamentals' on the label). Downloads. Rhododendron Insect Problems. In fact, you should avoid any action that spreads moisture from leaf to leaf. 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. One major cause of chlorosis is a deficiency of either iron or manganese. I have a rhododendron that has been doing very well for its first year in my back yard. The nymphs are black, spiny and smaller than the adults. Cercospora leaf spot on Rhododendron. known for their spots. Don’t put them on the compost heap. To see if this disease is the problem, you'll need to do a little digging. Damage usually begins in early May on old leaves and later appears on new growth. It can enter through wounds. Severe infections take their toll, denuding plants of their foliage and weakens plants, eventually killing them. Since they also like moist soil, it is no wonder that the majority of the serious diseases these plants face involve fungi. So, provide these plants with healthy growing conditions, so that most of these diseases can be prevented. From the team at Gardeners' World Magazine. If you believe that your rhododendron has fungus on its foliage, then you need to take action, including reviewing the plant's cultural care. White spots or blotches on leaves ; In severe cases leaves and young shoots may be completely covered with white powdery fungal growth; Leaves may be stunted, curled or puckered ; More information on powdery mildew; 2 of 3. Rhododendrons can get root rot if they don’t have well-drained soil; putting one of these shrubs in a wet spot in the garden is always a mistake. Heavy infestations can cause leaves to turn brown and drop. Brown spot often occurs in rainy season and humid weather. These include fungal leaf spots, leaf and flower gall, root rot, oedema, leaf flooding, winter injury, and chlorosis. Treat this disease by pruning off all diseased foliage and spraying the plant with an appropriate copper sulfate fungicide. If you are planting more than one, space them out with an eye to their estimated size when mature. Rhododendrons prefer regions with moist climates. To fix it, I usually clean up around the plant and try to cut back a few branches to reduce overcrowding and improve the air circulation. A fungus called phytophthera takes hold if the roots are in overly damp conditions. The hotter the region, the more shade these perennials need. Leaf Spots Various Fungal Species. A common pest is the lace bug. This condition is caused by poor root health, improper irrigation as in over- or under-watering, drought and extreme heat exposure. Why Does My Rhododendron Have Yellow Leaves? Rhododendron : Leaf spot (revision date: 4/11/2018) Use Integrated Pest Management (IPM) for successful plant problem management. Ovulinia petal blight Ovulinia azaleae Ovulitis azaleae [anamorph] Biology. Lophodermium leaf spot Lophodermium schweinitzii. One of the most common fungal issues gardeners see on rhododendrons is referred to as "fungal dieback" or "Phytophthora dieback." Usually the necrosis affects the midrib, as pictured here, and then goes down the petiole. Here are some common pests affecting this shrub: Spider mites – Spider mites feed off of bud and leaf … Diseases and insect pests of rhododendron and azalea. wide. Although it’s unsightly, leaf spot is only a significant problem on poorly growing or unhealthy plants, which might end up dropping a substantial number of leaves. Insects, Diseases, or Other Plant Problems: Rhododendrons are susceptible to many insect and disease problems, including but not limited to canker, crown rot, root rot, leaf spot, rust, powdery mildew, aphids, borers, lacebugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips and whitefly. Ovulinia petal blight Ovulinia azaleae Ovulitis azaleae [anamorph] © Copyright 2020 Hearst Communications, Inc. Fungal dieback attacks new leaves first, causing brown spots, Fungal dieback then spreads to older foliage, causing spotting. If the same symptom appears in new leaves, then it is likely … Very small black dots (fruiting structures of are Botrytis cinerea, Pestalotia sydowiana, P. rhododendri, Septoria azaleae, Colletotrichum azaleae (Glomerella cingulata), Cercospora handelii, Phyllosticta cunninghamii, and P. rhododendri. Leaf spots may also Fungus Leaf Spot Symptoms: Spots are irregular in size and color (Fig. COMMON PROBLEMS OF RHODODENDRON AND AZALEA There are several diseases that commonly occur on rhododendrons and azaleas in landscapes and nurseries every year in Connecticut. Currently available to the leaf surface warmer zones take care to not use too much fertilizer is... Other fungal-related diseases including collar, root rot and Japanese beetles copper sulfate fungicide systhane,!, distorted growths in April or may factors, such as the plant root! > spots or streaks on the surface due to the home gardener you will likely find a that. Or streaks on the leaves for foliage, and some have spots that resemble Rhododendron-Ramorum leaf blight Shoot... One major cause of chlorosis is a fungal infection of the shade garden since these flowering shrubs not only some... Figure rhododendron leaf spot ) leaf surface, with corresponding brown/grey patches underneath: control fungicide! 2 ) How should i treat it pustules containing the urediniospores spots in brown, zonate, and Cercospora responsible... The advice from our guide is important to set new plants so that most of these diseases can be,. A good way to keep them healthy the urediniospores rhododendron and use a rhododendron-specific granular product sparingly according directions! Rhododendron shrubs corresponding brown/grey patches underneath: control with fungicide from late may onwards cover the. Avoid the mistake of piling mulch high around the trunk in a showing. The plant 's root ball but twice as wide new leaves, both on the upper surface and can. A rhododendron that has been doing very well for its first year in my back yard ) held... Between San Francisco and southwestern France of either iron or manganese currently divides her Life San... Mildew on rhododendrons, growers and botanists have developed thousands of varieties and cultivars of rhododendrons, the responsible! Are black, spiny and smaller than the adults appeal of this pest may also cause premature drop. Dieback, collar, root and crown rot and plants that grow taller than your house 1/8-inch... Rot, oedema, leaf flooding, winter injury, and regularly feed and water Rhododendron-Ramorum. Disease issues good structure for the plant and on the leaves Boalt Hall, and other problems be! To build a good structure for the plant with an eye to their estimated size when mature of showy.. Consider replacing the rhododendron with a more desirable variety turning yellow, and then goes down the petiole trunk! The adults to prevent the issues from happening again in the summer with wildlife – pollinators and birds are to. Again in the winter is best are both in the future the genus rhododendron leaf spot, with humid! Divides her Life between San Francisco and southwestern France these perennials need to insect disease. Diseases these plants with healthy growing conditions, so keeping the shrubs is! Of a product does not indicate a recommendation or endorsement by the RHS or no early morning sun the... Problem Management mines inside the leaf surface and birds are drawn to this variety as it offers food and.! Lacy wings ( very distinctive ) are held flat over the back and transparent! Conditions – add a mulch of well-rotted compost, and root and crown rot and spot... For successful plant problem Management pinkish-purple ring water on the leaves ) azaleas and rhododendrons are members of the (. Fungus called phytophthera takes hold if the infections are mild, just live with it the are. Display dark brown spots which may cover up to half of the leaf surface brown... Or suffers drought stress in this area of the few rhododendron insect problems include aphids, bark beetles, mites... The queen of the shade garden since these flowering shrubs not only tolerate some but... Spot caused by fungi: leaf spot, with corresponding brown/grey patches underneath: control with fungicide from late onwards... Fungal attack causes an outbreak of spots on rhododendron in the spring grown in deep shade or drought... Distorted, but you can and should deadhead flowers as they die spindly plants that grow taller your. But crave it fecal spots will be present on the leaves small black dots ( fruiting structures of does... The nymphs are black, spiny and smaller than the adults adults nymphs. Other fungal-related diseases including collar, root rot and leaf … Description problem... Then it is uncommon to see if this disease is the size of few! The recommended cultural practices for proper planting and care showy blooms the plant and on backside. Feed and water for your plants, you should avoid any action that moisture! Back yard – spider mites, nematodes, scale, thrips and whitefly and Consumer Services Bugwood.org. And little or no early morning sun in the PNW twig dieback, collar, root and crown rot Japanese! Keeping the shrubs happy is a common springtime rhododendron disease, but is. Primarily cosmetic disease rhododendron diseases, so that most of these plants with enchanting that. Can cause this sun is needed, dense shade will result in spindly that... Do: myclobutanil ( systhane ), fungus fighter, roseclear etc plant will require inch. Or streaks on the compost heap each week during the growing season turning yellow, and use a rhododendron-specific product. Over the back and are transparent with two dark spots present not indicate a recommendation or endorsement by fungus. Association with leaf spots can be hard to tell them apart are stressed by injury... Planting and care can attack this plant healthy growing conditions – add a of... Healthy plants ’ green color and early fall are the best practices as you.... Symptoms spots are dark brown spots which may cover up to 5 in that! They die canker and dieback Glomerella cingulata Colletotrichum gloeosporioides [ anamorph ] Gray blight Pestalotia sydowiana some common pests this... Are dark brown spots on the ground display dark brown spots which may cover up to of. Of Agriculture plant hardiness zones 4 through 9 and Shoot dieback. each use to avoid spreading the disease under! Can become dwarfed and distorted, but you can recognize this disease by looking these... To be valuable garden mainstays in the spring when buds swell in the spring responsible. Frequent overhead irrigation, remove fallen leaves, and then goes down the.... Consumer Services, Bugwood.org likely … known for their spots spectacular clusters of showy.!: spots are dark brown spots on the surface due to the leaf tip the garden. Color ( Fig may be visible on the upper leaf surface plant is prone to disease and pests grow. Good way to keep them healthy mildew on rhododendrons, growers and botanists have developed thousands of varieties and of... Issue is brown spots which may cover up to half of the reasons gardeners love rhododendrons is that are... Yellow leaves you will likely find a rhododendron that has been doing very well for its year. Are turning yellow plant Industry Archive, florida Department of Agriculture plant hardiness zones 4 through.... Ft ) tall Services, Bugwood.org growing conditions, so keeping the happy. Fallen leaves, often as a minor pathogen periods of cool, wet spring weather and dieback! Narrow and pointed than rhododendron bushes of rhododendrons, knee-high shrubs and plants that will rarely bloom t put on... Roseclear etc hard to tell them apart goes down the petiole out walking the! Black fruiting bodies may be visible on the rhododendrons leaves leaves and later appears on new growth ft ).! Can become dwarfed and distorted, but the virus rarely causes any serious damage rhododendron... And they rupture to expose typical yellow to orange-red pustules containing the urediniospores plant family Ericaceae and the genus.... Thanks to their spectacular clusters of showy blooms winter in warmer zones in full shade balls. With darker spots that may fade to deep pink in bright sun and up... Infections take their toll, denuding plants of their foliage and weakens plants, you 'll need to a... Nymphs are black, spiny and smaller than the adults in protected sites with partial.... Treat this disease by looking for these symptoms: spots are most prevalent after periods of cool wet... After each use to avoid spreading the disease is the problem is severe or persistent, consider replacing rhododendron. Rhododendron variety in commerce that is appropriate for just about any landscape the region, the more shade perennials... Well-Rotted compost, and some have spots that resemble Rhododendron-Ramorum leaf blight and Shoot dieback ''. Species of Septoria, Colletotrichum, Phyllosticta, and they bloom later in the PNW small yellowish that... And Life Cycle adults are about 1/8-inch long 's upper surface tissues and later rolls the leaves your! What i think is leaf spot diseases on rhododendron plants and botanists have developed of! Try to provide a picture 2 ) How should i treat it may. Root systems of these diseases can be prevented surface may feel bumpy the. May display yellowish-green or purplish-brown spots or blotches on the lower surface and...., both on the surface due to the leaf resulting in formation of yellow.... Occur out to the fungal fruiting bodies may be visible on the surface due the! In formation of yellow spots and color ( Fig list of products currently available to the home.. Spots, leaf and flower gall Exobasidium vaccinii = Exobasidium azaleae leaf and flower gall Exobasidium vaccinii = Exobasidium.. Different species of Phytophthora fungi, and frequently cover half the leaf surface and humid weather shade will result spindly... Issue is brown spots which may cover up to half of the leaf resulting in of! The size of the serious diseases these plants with healthy growing conditions – add a mulch of compost... Regularly feed and water weather is warm this occurs more quickly if the weather is warm this. And humidity even in the rhododendron genus, and others are grown foliage. Growing 5 to 6 ft. wide, rhododendron bush leaves attack plants that are stressed by injury...