Beneficial nematodes are not effective on these borers. REC, Lower Eastern Shore Management: Rake and destroy fallen leaves in the fall to remove overwintering pupae. The adult moths, about ¼” long, resemble wasps, have mostly clear wings, and black bodies with 3 gold bands on the abdomen. 5) appears as small white cottony masses on the bark. Adult Japanese weevils feed during the day and will drop from the plants when disturbed. Originally written by Mary K. Malinoski, University of Maryland Extension Specialist. Native to China, Myanmar and Laos, Rhododendron decorum (Great White Rhododendron) is a very fragrant, large, evergreen shrub or small tree with attractive spring flowers, decorative bark and handsome dark green leaves. Damage usually begins in early May on old leaves and later appears on new growth. To check for the presence of whiteflies, shake the branches of symptomatic azaleas to flush out adult whiteflies which look like tiny white moths. Follow instructions on label for timing and soil temperatures. Do not apply horticultural oil within 30 days of a sulfur application; avoid applications on drought-stressed plants, and on windy days or when temperatures are below 32 degrees Fahrenheit or above 90 degrees F. Follow manufacturer recommendations for preparation and dilution rate, typically 1 to 3 percent, and test out the material on a small, inconspicuous part of the shrub before applying it more broadly. The females appear totally white when they produce their white, waxy egg sacs. 'Patty Bee': Has scaly foliage, like an azalea, that turns maroon in winter. Calyx 5-parted, often very small, persistent. Photo: Jim Baker, North Carolina State University, Bugwood.org. Gall midge larvae feed on the developing leaf tissue causing leaves to become distorted with puckered and curled margins. Scale – Scale insects commonly cause black fungus on rhododendron. Adult beetles feed on the underside of leaves on the midvein, causing the leaves to curl. Boring larvae may cause branches to crack. Overwintering immature scales (nymphs) are less than ⅛-inch long, gray, and are usually found in twig forks. The borer causes wilting of leaves and twig dieback. Mulch with chopped oak leaves, leaf mold, or pine needles and water deeply during drought periods. Black Vine Weevil (adult). Many diseases and other problems can be prevented by following the recommended cultural practices for proper planting and care. When lace bug populations are high, sprays of horticultural oil (at a 2% summer rate) or insecticidal soap will control lace bugs if the lower surfaces of the leaves where lace bugs are active are thoroughly covered. Two-banded Japanese weevil (actual size is 3/16 inch). More on Mildew by Fred Minch Pests Of Rhododendrons by Arthur L. Antonelli All stages occur on the undersides of leaves. Systemic insecticides applied to soil are also highly effective but follow cautionary warnings on label to protect pollinators visiting azaleas and rhododendrons. This scale primarily attacks azalea and rhododendron, but also has been found on andromeda, maple, arborvitae, willow, poplar, and hackberry. White Rhododendron, with a bumblebee. Azalea, rhododendron, and andromeda each have their unique species of lace bug. Studies in Connecticut indicate as many as three to five generations annually depending on climatic conditions. The azalea bark scale, Eriococcus azaleas, is a prominent pest of rhododendron, azalea, and huckleberry (Vaccinium spp.). To control heavy infestations, spray dormant plants with a 4% rate of horticultural oil to kill developing nymphs on twigs. Scales appear as mounded white lumps on rhododendrons in early summer and early fall. Signs of beneficials insects may be active lady beetle adults or larvae, lacewing larvae, or parasitoids indicated by small circular holes on the immature whiteflies. Alternatively, place bait stations or stakes with a slow-acting active ingredient near the base of the shrub where you observe ant trails. Branches or entire plants may be defoliated. How to Treat Scale on Shrubs. Photo: M. Raupp, University of Maryland. Lacebugs perfer sunny areas so plant in more shaded areas if possible. As larvae mature they curl the tips of the leaves with silk and feed inside the curl. Management: Look for caterpillars when chewing damage occurs. Reaching a height of 3-4 feet, the White Rhododendron is an easy-to-grow evergreen shrub that thrives in partial sunlight and needs only occasional pruning. This scale primarily attacks azalea and rhododendron, but also has been found on andromeda, maple, arborvitae, willow, poplar, and hackberry. In spring, adults emerge from the soil and fly to the tips of branches where they lay eggs in new developing leaf tissue. Scales are unusual insects. (Bt), a microbial insecticide, that is specific for young caterpillars and is sold under various trade names. Curled leaf tips in June indicate the completion of the first generation. 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. Azalea bark scale (Fig. 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. Photo: University of Maryland Extension, Rhododendron Borer (adult). The most common pests of rhododendrons and azaleas in Maryland are lace bugs, azalea bark scale, rhododendron borer, and weevils. They were first discovered by a Flemish botanist, Charles l’Ecluse. 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. Black fecal spots will be present on the lower sides of stippled leaves. Photo: John Davidson, University of Maryland, Rhododendron borer is the larvae (caterpillar) of a clear wing moth. 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. The females appear totally white when they produce their white, waxy egg sacs. Azaleas are visited by pollinators. Adult beetles feed for two to three weeks before laying eggs. Mature larvae are about 1/2 inch long, white with brown heads. The largely immobile nature of scales and their protective covering makes chemical control challenging. 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