Fungus or disease? Improper pruning can increase your risk of cankers. Root and crown rots, which are also called water molds, attack azaleas at their base and can often kill plants. First of all, take solace in the fact that their bark is worse than their bite. Under severe conditions, the spots may coalesce and form large irregular spots. As cankers girdle twigs or branches, they cut off nutrient transport and woody parts die. Fungicides are used t… This is a pest that generally does not kill hosts, rather it causes aesthetic damage. Well-drained, organic soils with a pH of 4.5 to 5.5 are best suited for azaleas. Sometimes there are environmental factors that are associated with azalea problems. hmbs53 Melrose, FL May 29, 2008. While there is currently nothing available to control nematodes on azaleas, with proper fertility and watering practices, the plants are better able to tolerate attacks. Rhododendron spp. Azalea. * Reprinted by permission from Compendium of Rhododendron and Azalea Diseases, second edition, ISBN 0-89054-436-0 , published by the American Phytopathological Society. Lacebugs feed by sucking chlorophyll from the leaves of many plants. Prune below the discoloration and discard the infectious stems. As alien-looking and repulsive as azalea leaf galls are, they are not considered overly serious. Control is often accomplished through handpicking, as they pose no threat to humans. Treating Azalea Dieback. When the upper surface of rhododendrons or azalea leaves have a graying mottled appearance, there is probably a heavy infestation of lacebugs, Stephanitis sp. In humid climates or during periods of frequent rainfall, you can apply preventive fungicides such as Chlorothalonil to prevent fungi from forming. Petal blight is caused by an airborne fungus which over-winters on the spent flowers. While these attractive plants are generally hardy and problem free, they are occasionally bothered by pests and diseases. Soils. Azalea Bark Scale, Eriococcus azaleas, was discovered in 1881 and is a major yearly pest for Azaleas, Rhododendrons, and Huckleberries. As a tradeoff for this striking display, azaleas must contend with a variety of fungal diseases that threaten their health and mar their beautiful blossoms. Death of branches with split bark may not occur until weeks or months after the injury. Drench soil area under plants with Terraclor in January. To treat, eliminate the insects and prune any dead or dying parts of the plant. Affected leaves may also curl up and drop. It has been reported in the Eastern US, as well as Belgium and Russia. Dying leaves and stems. Informational table showing disease name, symptoms, pathogen/cause, and management of Azalea and Rhododendron diseases. If your shrubs have tight growth, pruning out limbs to open plants increases air circulation. Twig Blight – Twig blight may cause wilting and defoliation on one or more branches with a reddish-brown discoloration under the bark. Signs of Azalea Dieback. Too much or too little light can also damage these plants. Bark and branches fall prey to this disease after fungi enter through natural openings or wounds. ), Clemson Cooperative Extension: Azalea & Rhododendron Diseases. Fungi on azaleas can sometimes be sidestepped by applying preventive fungicides. This fungus is a water mold, and thrives in poorly drained or wet conditions. When crushed, these scales exude pink “blood”-like liquid. Spray with Thylate or Benomyl when blooms begin to open. May require fungicide spray. What to Do About Azalea Leaf Galls . © Copyright 2020 Hearst Communications, Inc. 4 through 6). Bot canker, which is caused by the fungal pathogen Botryosphaeria dothidea, attacks woody parts of azaleas. Lichens are composed of a fungus and an alga living together cooperatively. Janet Flower Shop Network Plant Expert Reply: First we need to determine if you really have a fungus. Although the pest usually does not kill the host tree, it causes aesthetic damage, weakens the tree, and can cause honeydew and sooty mold to develop. Many people enjoy the color and patterns lichens create. Applying a methyl bromide soil drench may manage water molds, but once above-ground symptoms appear, such as yellowing and dropped leaves, chemicals are usually ineffective. It has been reported in the Eastern US, as well as Belgium and Russia. Canker Diseases: Canker Diseases are caused by fungi that commonly enter the tree through wounds in the bark or branch stubs. related pages> Azalea Problems (parent page) The fungus Phytophthora species causes one of the most common disease problems in the landscape for rhododendron and azalea. Diseased leaves may drop prematurely. Azalea Lace Bugs – These are one of the most common threats to azalea shrubs. Anthracnose – Leafspot and Dieback (fungus – Glomerella cingulata): Symptoms on leaves are characterized by numerous small, round spots on both leaf surfaces. The spots are light to rusty-brown with a definite margin. https://www.giroudtree.com Azalea Bark Scale can destroy beautiful Azalea shrubs. This disease causes rhododendron and azaleas to first have white powder-like spots on young leaves, which can spread to the entire upper and lower surfaces of the leaf. Fungal blight diseases infect azalea flowers and are particularly problematic if you use overhead irrigation. Drought can cause similar symptoms. Azalea bark scale looks like, and is often mistaken for mealybugs. After studying botany and microbiology at Clemson University, Blackstone was hired as a University of Georgia Master Gardener Coordinator. Since lichens are almost always found on weak plants, do lichens cause the plants to become sick? The algae makes food from sunlight and air; the fungus protects the algae and supplies moisture. Azaleas (Rhododendron spp.) Crape myrtle bark scale is relatively easy to identify. Infested azaleas usually appear chlorotic, and severe infestation of azalea bark scale can weaken or kill your azaleas. Eriococcus azaleae Discovered in 1881, the azalea bark scale, Eriococcus azaleas, is a prominent pest of rhododendron, azalea, and huckleberry (Vaccinium spp.). Photo credit: A.L. Insecticidal soap is usually effective in controlling lace bugs in late spring or fall. A wilted plant is usually the first sign of trouble. herald spring with a profusion of flowers in U.S. Department of Agriculture plant hardiness zones 5 through 9. Quote. Nutrient deficiencies are another common factor with azaleas. Treatment with horticultural oil … Close-up of Azalea bark scale egg masses on infested branches blackened by sooty mold. Interestingly, a lichen is a “sandwich” made of algae in the center and fungus on the outside. Various scales attack azaleas and rhododendrons, but one of the most common is azalea bark scale (Eriococcus azaleae). Blackened branches, covered by a sticky soot and white, cottony fluffs in the crotches of the lower branches are all symptoms of one of the most dreaded of azalea diseases. Whiteflies do not respond well to treatment; however, neem oil may reduce populations. The azalea bark scale, Eriococcus azaleae Comstock, can be found on a variety of hosts grown in nurseries and landscapes including azalea, rhododendron, andromeda, hawthorn, poplar, willow, and most recently, it has been found infesting blueberries in the Pacific northwest. Azalea Leafminers – This azalea plant pest generally “mines” between the upper and lower surfaces of leaves causing brown blisters or yellowing on the leaves. Removal of affected plants may be necessary. Plants may exhibit discoloration with fewer or undersized foliage and flowers. More » This scale is most obvious from May through June when white egg sacs may be found in twig forks. Petal Blight – This fungus only affects flowers and appears as pale or whitish spots on colored petals or rust-colored spots on white petals. Rust – Rust is a fungal disease that causes reddish to orange spore masses on infected leaves, as well as galls or cankers on bark, which may occasionally kill the entire plant. Nitrogen and iron are the most commonly seen deficiencies in azaleas. 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