These caterpillars are black with rows of white or pale yellow spots, reddish brown legs, head and neck area and are 2 1/2 inches when mature. (This was diagnosed from a photo I sent to your service a couple of years ago.) Adults are present in June and July. Cottony camellia scales, Pulvinaria floccifera, are cream to tan, elongate oval, and relatively flat.They are also called cottony taxus scales as this scale is a fairly common pest of yew. Photo: Photo: M. Raupp, University of Maryland. Antonelli, et al. Mulch with chopped oak leaves, leaf mold, or pine needles and water deeply during drought periods. It has been reported in the Eastern US, as well as Belgium and Russia. Management: Rake and destroy fallen leaves in the fall to remove overwintering pupae. Azalea Leafminer (early instar) inside of a leaf. Heavy infestations over several seasons may kill plants. Adult Japanese weevils feed during the day and will drop from the plants when disturbed. To control heavy infestations, spray dormant plants with a 4% rate of horticultural oil to kill developing nymphs on twigs. Azalea Lace Bug (Stephanitis pyriodes) andRhododendron 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. Rhododendrons and azaleas are some of the most popular spring-flowering shrubs in the landscape, and healthy plants can give years of pleasure. Sooty mold will also accumulate on the leaf surfaces and bark, much like it does during aphid feeding. Wrap several branches that are infested with scales tightly with narrow bands of double-sided sticky tape in late winter or early spring. In this case, the leaves, buds, or stems, develop swollen growths with distorted shapes. Photo: M. Raupp, University of Maryland. The larvae are whitish and have no visible head. 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. The larvae bore down the center of twigs causing individual branches to wilt, and eventually die back to the ground. Photo: Dow Gardens, Bugwood.org. REC, Western Maryland Two-banded Japanese weevil (actual size is 3/16 inch). If there are no yellowing leaves, no treatment is necessary. White prunicola scale is most partial to members of the Prunus species, peach chinaberry, flowering peach, French mulberry, and persimmon. Azalea leafminer overwinters as pupae in the leaf mines. Leaves olive green, 20 x 8 cm. All types of fruit and ornamental trees, shrubs. Most adult scales do not move, they look like brown or white “tortoise shells” on branches or foliage. Frass (sawdust-like material) indicating the presence of rhododendron borer. Scale Download a PDF of this article Plants Affected. 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. The following azalea cultivars have shown resistance to azalea lace bug damage: ‘Autumn Amethyst’, ‘Autumn Twist’, ‘Autumn Royalty’, ‘Autumn Sangria’, ‘Autumn Cheer’, ‘Indica alba’, ‘Flame Creeper,’ and ‘Delaware Valley White’, among others. Boring larvae may cause branches to crack. Management: Look for caterpillars when chewing damage occurs. Their feeding causes leaf margins to curl and the maggots complete their development within the curled leaf tissue. Be sure to observe all cautionary statements on labels to protect pollinators. Eggs hatch into tiny white maggots less than 1/16 inch in length. There is one generation a year and all stages overwinter in the soil. These pests generally appear on plants as immobile bumps with no recognizable body parts. Whitefly adults and nymphs feed on the underside of the foliage. How to Treat Scale on Shrubs. Plan to spray the shrub once the number of crawlers trapped begins to decline. If necessary a 2% summer rate of horticultural oil may be applied in July after all of the eggs have hatched. Borne at the tips of the upright branches, the blossoms contrast beautifully with the evergreen foliage of rounde… Apply either spray when caterpillars are numerous and young (less than 3/4 of an inch long). Older and more established rhododendrons may need a chainsaw to cut through the large woody branches, especially toward the middle of the plant. Diligent, yearly removal of infested leaves may dramatically reduce damage in a few years. Photo: Jim Baker, North Carolina State University, Bugwood.org. Black Vine Weevil (adult). The moths are 3/8 inch long and yellowish brown. Small plants when heavily infested may be defoliated. The second generation mines begin in July. Apply either spray when caterpillars are numerous and young (less than 3/4 of an inch long). Scale insects also secrete a sticky liquid called honeydew, which promotes the fungal disease black sooty mold. This tiny fly attacks the new growth of rhododendrons. Scales are unusual insects. Small shrubs may be defoliated in heavy infestations. Apply a sticky, nondrying compound intended for trapping insects in a band around the main stem or stems of the shrub. See the package for specific instructions. Watching the white mounds during hatching season will reveal the small crawlers moving along the plant searching for a spot to suck the sap. The borer causes wilting of leaves and twig dieback. Black fecal spots will be present on the lower sides of stippled leaves. There are multiple generations of lace bug per year. Eggs, crawlers and adults under the wax are red. Fully developed larvae drop to the ground where they will pupate. Lacebugs perfer sunny areas so plant in more shaded areas if possible. Overwintering immature scales (nymphs) are less than ⅛-inch long, gray, and are usually found in twig forks. Flowers 5-merous, usually in terminal corymbs. 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. A registered insecticide (e.g., Imidacloprid) may be applied by a certified pesticide applicator only (as per the Maryland Pollinator Protection Act.). As soon as you notice the black fungus on rhododendron shrubs, check the leaves carefully to determine which insect is responsible and treat it appropriately. Inspect for adult weevils at night using a flashlight. A currently registered systemic insecticide may be necessary where coverage of the undersides of leaves is difficult. 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. The underside will show a brownish residue. Buds with several to many imbricate scales. Adult lace bugs are flat, about 1/8 inch long, with transparent lace-like wings. Video shows close ups of Azalea Bark scale and provides some plant inspection tips. Continue changing the double-sided tape and observing crawler numbers. Water the infested shrubs deeply and infrequently during extended dry spells. Curled leaf tips in June indicate the completion of the first generation. The azalea bark scale, Eriococcus azaleas, is a prominent pest of rhododendron, azalea, and huckleberry (Vaccinium spp.). The females appear totally white when they produce their white, waxy egg sacs. Damage caused by the stem borer, which includes wilting terminals and dieback, is similar to the Rhododendron borer. Pull mulch back prior to application. Studies in Connecticut indicate as many as three to five generations annually depending on climatic conditions. Rhododendron borer is the larvae (caterpillar) of a clear wing moth. Calyx 5-parted, often very small, persistent. They were introduced to the European Alps and thus the name, Alpine Rose (Rhododendron histru… If control is necessary, use a registered insecticide when damage begins in mid-June. If so, you have a fungus called powdery mildew. Azalea Bark Scale, Eriococcus azalea: This insect prefers azalea or rhododendron but can infest andromeda, maple, willow, poplar and other plants. White flowers grow on top of the previous year's growth and tucked underneath the leaves from the current year. The borer causes wilting of leaves and twig dieback. Mature larvae are 1/2 inch long and yellowish brown. The leaves become covered with honeydew, followed by sooty mold (a black coating). Beneficial nematodes may be effective in controlling larvae in the soil. Members of the genus Rhododendron support the following specialized bee: Andrena (Andrena) cornelli. Symptoms/Damage. Central Maryland Azalea leafminer overwinters as pupae in the leaf mines. Plant azaleas in partial sun (morning sun and afternoon shade). Damage occurs in late summer and fall. Severe scale feeding causes stress and affected plants appear thin and unthrifty. To check for the presence of whiteflies, shake the branches of symptomatic azaleas to flush out adult whiteflies which look like tiny white moths. Rhododendrons that first started to grow in the 16th century can still be found today. Common problems of rhododendron bushes can be avoided by providing the best growing environment possible and maintaining a consistent pruning, mulching and fertilizing program. Azalea lace bug damage. Thoroughly cover the infested plant, making sure you completely reach leaf undersides, twigs and other parts of the plant infested with scales. A small brown insect with transparent wings sucks on the bottom of the leaf causing a mottled appearance on the top with yellowish, brownish or white spots. Photo: John Davidson, University of Maryland. Look for discoloration of foliage and signs of sooty mold to indicate the presence of the scales. There are no conventional insecticides that will kill stem borer larvae once they are inside the branches. Follow instructions on label for timing and soil temperatures. Description. Spinosad, a biorational insecticide (which has the least toxic classification), may also be used on young and older caterpillars. Honeydew can … 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. Mature larvae are about 1/2 inch long, white with brown heads. A scale infestation is indicated by sooty mold on leaves, yellowing of leaves, and twig dieback. Janet Flower Shop Network Plant Expert Reply: First we need to determine if you really have a fungus. As larvae mature they curl the tips of the leaves with silk and feed inside the curl. Healthy shrubs can usually withstand some amount of scale feeding, but a heavy infestation can force leaves to wilt, turn yellow and drop prematurely. They may be injected into the active borer tunnels. Examine egg sacs for holes which indicates control by parasitoids, and look for predators such as ladybird beetles. Azalea Bark Scale. Look for nymphs and black fecal spots on lower leaf surfaces in early May to estimate potentially damaging populations. The adult moths, about ¼” long, resemble wasps, have mostly clear wings, and black bodies with 3 gold bands on the abdomen. This borer prefers rhododendron, but occasionally attacks deciduous azalea and mountain laurel. Heavy infestations of lace bug may cause leaves to turn yellow and then brown. Whiteflies would be found underneath the leaves. Azalea lace bug adult and fecal spots. The pale white flowers that sprout from this plant offer a slight citrus scent. Management: Rake and destroy fallen leaves in the fall to remove overwintering pupae. This borer prefers rhododendron, but occasionally attacks deciduous azalea and mountain laurel. Heavy infestations cause wilting and eventual branch dieback. They vary in appearance depending on age, sex, and species. If soft scales are present on the shrub and producing a large quantity of honeydew that is attracting ants, plan to control the ants, because they protect the scales from their natural enemies. Decide what tool you need for your rhododendron size. Control. Photo: University of Maryland Extension, Rhododendron Borer (adult). Mature larvae are 1/2 inch long and yellowish brown. Their feeding causes leaf margins to curl and the maggots complete their development within the curled leaf tissue. Blooming in mid spring, each cluster (or truss) can hold up to 3-5 attractive, trumpet-shaped violet-blue flowers, whose color intensifies with age. The most common pests of rhododendrons and azaleas in Maryland are lace bugs, azalea bark scale, rhododendron borer, and weevils. If the infestation is light, little or no plant symptoms are evident, and if beneficial insects are present, spray the undersides of leaves with insecticidal soap or horticultural oil at the 2% summer rate. Damage occurs in late summer and fall. Females are approximately 1/8-inch long White felt-like sacs are secreted in May that enclose the body and eggs. Hosts include andromeda, azalea, rhododendron, hawthorn, poplar, willow, and most recently, blueberry in the Pacific Northwest. Many diseases and other problems can be prevented by following the recommended cultural practices for proper planting and care. Overwintering immature scales (nymphs) are less than ⅛-inch long, gray, and are usually found in twig forks. This scale primarily attacks azalea and rhododendron, but also has been found on andromeda, maple, arborvitae, willow, poplar, and hackberry. Various scales attack azaleas and rhododendrons, but one of the most common is azalea bark scale (Eriococcus azaleae). Rhododendrons and azaleas, in general, grow best in landscape conditions that mimic natural mountain habitats: acidic soil (pH between 4.5 - 5.5), good drainage, ample soil moisture and organic matter, understory areas with light shade, cool soil temperature, and protection from strong winds. Spray the young lacebug nymphs off the leaves as they hatch. Adult feeding damage appears in late April and early May as adults become active and notch leaf margins on azalea and rhododendron. Susceptible cultivars include those of Rhododendron catawbiensis and R. maximum. Heavy infestations cause the margins of terminal leaves to cup. Damage is indicated by the presence of blotch mines in leaves of azalea beginning in May. Gall Midge damage. NPS Photo. Blend 5 tablespoons of an ultra-fine horticultural oil with a gallon of water, and use a garden sprayer to thoroughly spray the infested plants once you observe a decline in the number of scales trapped. 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. Scale insects feed on shrubs' sap using their long, piercing mouthparts, causing twig and branch dieback and sometimes killing the plants. giganteum, reported to 30 m (100 ft) tall. This deformation will last as long as leaves remain on the plant. Alternatively, place bait stations or stakes with a slow-acting active ingredient near the base of the shrub where you observe ant trails. There is one generation per year in Michigan. The larvae overwinter in branches the first year and in roots the second year. Soil applied insecticides can harm ground beetles which are beneficial natural predators of a variety of pests. Photo: Bruce Watt, University of Maine, Bugwood.org. Cushion scale is a sap-sucking insect that feeds on the foliage of mainly evergreen trees and shrubs, especially camellia, rhododendron, Trachelospermum, Euonymus japonicus and holly. Broadleaf evergreen, 6 ft (1.8 m) in 10 years, upright, vigorous, grows to a large plant. The best management option for residents with only a few plants is to prune out and destroy wilting branches when beetle larvae are in the branches in early spring or late summer. This whitefly is usually limited to azalea varieties that have hairy leaves. Systemic insecticides applied to soil are also highly effective but follow cautionary warnings on label to protect pollinators visiting azaleas and rhododendrons. Weevils can be hand-picked and dropped into a container of soapy water for disposal. Beneficial nematodes, available under several trade names, are a control option. Azalea whitefly damage. This is a pest that generally does not kill hosts, rather it causes aesthetic damage. In the past 2 years I pruned some of the worst infested branches and applied a 2% horticultural spray once or twice per year, I think in the summer and late fall, but I don't remember exactly when. Adult beetles feed for two to three weeks before laying eggs. These infested leaves will eventually turn yellowish and appear wilted. Heavy larval populations may cause stunting, wilting, and may kill small shrubs and tree seedlings. Black vine weevil feeding damage (leaf notching) to rhododendron. Rhododendron gall midge immatures spend the winter and early spring in the soil where they complete development and pupate. Adult beetles feed on the underside of leaves on the midvein, causing the leaves to curl. Do not apply broad-spectrum, persistent pesticides to attempt to control scale insects or other pests, as these chemicals will injure the populations of beneficial scale predators and parasites. White Rhododendron, with a bumblebee. 5) appears as small white cottony masses on the bark. 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. Prune the suspected branches and split them open longitudinally to see if larvae are present. To check for adults, place a tray under damaged shrubs and shake the plants. The moths are 3/8 inch long and yellowish brown. Adult feeding damage is very similar to that of black vine weevil but notches on leaf margins tend to be smaller. They were first discovered by a Flemish botanist, Charles l’Ecluse. 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