If necessary a 2% summer rate of horticultural oil may be applied in July after all of the eggs have hatched. Make any pruning cuts slightly angled and next to a junction with another branch or main stem. How to Kill Borers on Weeping Cherry Trees, Sooty Mold Caused by Whiteflies on Rhododendron Stems, How to Kill Aphids on Aureo Variegated Boxwood, University of California Statewide Integrated Pest Management Program: Scales, Purdue University Cooperative Extension: Scale Insects on Shade Trees and Shrubs, Colorado State University/Denver County Master Gardeners: Scale Insect Pests, How to Kill Spider Mites and Whiteflies on Shrubs. Black vine weevil feeding damage (leaf notching) to rhododendron. 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 caterpillars feed in groups when young and disperse as they mature. Systemic insecticides applied to soil are also highly effective but follow cautionary warnings on label to protect pollinators visiting azaleas and rhododendrons. This scale is most obvious from May through June when white egg sacs may be found in twig forks. Boring larvae may cause branches to crack. Susceptible cultivars include those of Rhododendron catawbiensis and R. maximum. The adult beetles are about 5/8 inch long, have long antennae, and are pale yellow with two black spots on the thorax and on the margins of the wing covers. Mulch with chopped oak leaves, leaf mold, or pine needles and water deeply during drought periods. Properly timing any sprays for when the scales are in their active crawler stage is important. Photo: Dow Gardens, Bugwood.org. Janet Flower Shop Network Plant Expert Reply: First we need to determine if you really have a fungus. … The adult female azalea bark scale is dark red with a long sucking mouthpart. Older and more established rhododendrons may need a chainsaw to cut through the large woody branches, especially toward the middle of the plant. Females are approximately 1/8-inch long White felt-like sacs are secreted in May that enclose the body and eggs. As larvae mature they curl the tips of the leaves with silk and feed inside the curl. Symptoms/Damage. Fully developed larvae drop to the ground where they will pupate. The underside will show a brownish residue. This scale primarily attacks azalea and rhododendron, but also has been found on andromeda, maple, arborvitae, willow, poplar, and hackberry. Photo: Bruce Watt, University of Maine, Bugwood.org. Heavy infestations cause the margins of terminal leaves to cup. Boring larvae may cause branches to crack. Mature larvae are 1/2 inch long and yellowish brown. Female scales are dark red, but remain hidden under the white mass. The moths are 3/8 inch long and yellowish brown. Immature lace bugs (nymphs) are black and covered with spines. (Bt), a microbial insecticide, that is specific for young caterpillars and is sold under various trade names. Photo: John Davidson, University of Maryland. Photo: John Davidson, University of Maryland, Rhododendron borer is the larvae (caterpillar) of a clear wing moth. Rhododendron 'Charles Dickens'. Curled leaf tips in June indicate the completion of the first generation. Plant azaleas in partial sun (morning sun and afternoon shade). The larvae bore down the center of twigs causing individual branches to wilt, and eventually die back to the ground. Rhododendron Linnaeus Evergreen or deciduous shrubs with alternate, entire or ciliateserrulate, glabrous to tomentose, lepidote or strigose leaves. Adult feeding damage appears in late April and early May as adults become active and notch leaf margins on azalea and rhododendron. Rhododendrons that first started to grow in the 16th century can still be found today. Flowers are a deep rose-pink, funnel-shaped, to 10 cm wide, 10-12 per cluster. Gall Midge damage. Mature larvae are about 1/2 inch long, white with brown heads. 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. Scale insects also secrete a sticky liquid called honeydew, which promotes the fungal disease black sooty mold. Prune off portions of the shrub that are heavily infested with scales if the scales are largely concentrated on a limited number of branches. Damage occurs in late summer and fall. Inspect plants for signs of early damage and remove curled leaves promptly. Azalea bark scale (Fig. Photo: Photo: M. Raupp, University of Maryland. There is one generation a year and larvae overwinter in tunnels in branches. And soil temperatures any sprays for when the scales to prevent populations from increasing 1/16 inch in length quickly... 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