REC, Western Maryland Numerous species of scale insects, typically classified as soft or armored, can attack a broad array of shrubs. White Rhododendron Rhododendron albiflorum. Damage on new foliage will be evident in May and July. Revised and edited by Dr. Michael J. Raupp and Dr. Paula M. Shrewsbury, University of Maryland, April 2020. Photo: David Held, Auburn University, Bugwood.org. Azalea whitefly damage. 5) appears as small white cottony masses on the bark. blooms drifting above dense branches of lush green foliage illuminate countless spring gardens with weeks of color. Make any pruning cuts slightly angled and next to a junction with another branch or main stem. Damage is indicated by the presence of blotch mines in leaves of azalea beginning in May. Management: Look for caterpillars when chewing damage occurs. Apply either spray when caterpillars are numerous and young (less than 3/4 of an inch long). Rhododendron Diseases by R. K. Jones and D. M. Benson Azalea & Rhododendron Diseases by Clemson University Cooperative Extension Common Problems of Rhododendron and Azalea by Dr. Sharon M. Douglas How To Identify Rhododendron and Azalea Problems by A.I. Heavy infestations cause wilting and eventual branch dieback. This borer, however, is a longhorned beetle. Is the white substance powdery and can you wipe it off. They were first discovered by a Flemish botanist, Charles l’Ecluse. Insecticidal soap may also be used. This scale is most obvious from May through June when white egg sacs may be found in twig forks. A registered insecticide (e.g., Imidacloprid) may be applied by a certified pesticide applicator only (as per the Maryland Pollinator Protection Act.). Broadleaf evergreen, 6 ft (1.8 m) in 10 years, upright, vigorous, grows to a large plant. Prune the suspected branches and split them open longitudinally to see if larvae are present. She holds a Bachelor of Arts in urban and regional studies. The larvae bore down the center of twigs causing individual branches to wilt, and eventually die back to the ground. Adults are present in June and July. Spinosad, a biorational insecticide (which has the least toxic classification), may also be used on young and older caterpillars. Fully developed larvae drop to the ground where they will pupate. There is one generation a year and larvae overwinter in tunnels in branches. The largely immobile nature of scales and their protective covering makes chemical control challenging. The females appear totally white when they produce their white, waxy egg sacs. Black fecal spots will be present on the lower sides of stippled leaves. If only a few caterpillars are present, pick them off by hand. Healthy shrubs can usually withstand some amount of scale feeding, but a heavy infestation can force leaves to wilt, turn yellow and drop prematurely. The adult weevils are about 3/16 inch long, brown, broadly oval, thick bodied, and brown to gray with two darker bands across the wing covers. They may be injected into the active borer tunnels. In spring, adults emerge from the soil and fly to the tips of branches where they lay eggs in new developing leaf tissue. Lacebugs perfer sunny areas so plant in more shaded areas if possible. Two-banded Japanese weevil (actual size is 3/16 inch). Prune off portions of the shrub that are heavily infested with scales if the scales are largely concentrated on a limited number of branches. Photo: Dow Gardens, Bugwood.org. Adult Japanese weevils feed during the day and will drop from the plants when disturbed. Black vine weevil feeding damage (leaf notching) to rhododendron. There is one generation a year and larvae overwinter in tunnels in branches. Black Vine Weevil (adult). Rhododendron varieties with resistance to weevils are available and include species such as Rhododendron cuneatum, R. dauricum, R. fastigiatum, and others.Black Vine Weevil (adult and larva). Large populations cause leaves to brown and drop prematurely. Rhododendrons and azaleas are some of the most popular spring-flowering shrubs in the landscape, and healthy plants can give years of pleasure. We embody the University's land-grant mission with a commitment to eliminate hunger, preserve our natural resources, improve quality of life, and empower the next generation through world-class education. Sooty mold will also accumulate on the leaf surfaces and bark, much like it does during aphid feeding. Photo: Jim Baker, North Carolina State University, Bugwood.org. Preferred host plants are azaleas, but they may also attack witch hazel, sumac, apple, red oak, and andromeda. Azalea Leafminer (early instar) inside of a leaf. Buds with several to many imbricate scales. Boring larvae may cause branches to crack. Most adult scales do not move, they look like brown or white “tortoise shells” on branches or foliage. Damage occurs in late summer and fall. Mature larvae are about 1/2 inch long, white with brown heads. It may also attack boxwood, catalpa, cherry laurel, euonymus, forsythia, Japanese flowering cherry, ligustrum, lilac, magnolia, privet, red twig dogwood, rhododendron, salix spp., and walnut. Adult feeding damage is very similar to that of black vine weevil but notches on leaf margins tend to be smaller. They were introduced to the European Alps and thus the name, Alpine Rose (Rhododendron histru… (Bt), a microbial insecticide, that is specific for young caterpillars and is sold under various trade names. Damage occurs in late summer and fall. Azalea Bark Scale. Angela Ryczkowski is a professional writer who has served as a greenhouse manager and certified wildland firefighter. Fully developed larvae drop to the ground where they will pupate. Heavy infestations cause the margins of terminal leaves to cup. Scale insects also secrete a sticky liquid called honeydew, which promotes the fungal disease black sooty mold. Follow instructions on label for timing and soil temperatures. Many diseases and other problems can be prevented by following the recommended cultural practices for proper planting and care. Adult beetles feed on the underside of leaves on the midvein, causing the leaves to curl. Heavy infestations over several seasons may kill plants. Weevils can be hand-picked and dropped into a container of soapy water for disposal. © Copyright 2020 Hearst Communications, Inc. Make sure shrubs receive an inch of water weekly through rainfall and supplemental irrigation, or water whenever soil about 3 inches below the soil surface near the shrub feels dry to the touch. giganteum, reported to 30 m (100 ft) tall. There are as many of four generations of azalea lace bug during the growing season and into the fall. This borer prefers rhododendron, but occasionally attacks deciduous azalea and mountain laurel. Interior leaves usually show most damage. Healthy plants that are not under water stress can better withstand and recover from scale feeding. Gall midge larvae feed on the developing leaf tissue causing leaves to become distorted with puckered and curled margins. There are multiple generations of lace bug per year. Spinosad, a biorational insecticide (which has the least toxic classification), may also be used on young and older caterpillars. Plan to spray the shrub once the number of crawlers trapped begins to decline. Management: Rake and destroy fallen leaves in the fall to remove overwintering pupae. A common shrub, also known as Cascade Azalea, found in the park on open slopes and meadow edges above 3,500 feet (1,066 meters). All types of fruit and ornamental trees, shrubs. Check inner branch forks in May and June for the white egg sacs and for reddish crawlers in late June into July. Insect problems include aphids, borers, lacebugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips and whitefly. Female scales are dark red, but remain hidden under the white mass. The pale white flowers that sprout from this plant offer a slight citrus scent. Rhododendron varieties with resistance to weevils are available and include species such as, A registered insecticide (e.g., Imidacloprid) may be applied by a certified pesticide applicator only (as per the, Rhododendron gall midge immatures spend the winter and early spring in the soil where they complete development and pupate. Boring larvae may cause branches to crack. If hand removal is not feasible, spray shrubs with Bacillus thuringiensis (Bt), a microbial insecticide, that is specific for young caterpillars and is sold under various trade names. If hand removal is not feasible, spray shrubs with. 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