Damage-Twigs and small branches are preferred by the rhododendron borer. The longevity of the adult usually ranges from 90 to 100 days. Categories Insect Pests, Shrubs Tags insects, native plants, pesticides, rhododendron, stem borers. Find more information at the following NC State Extension websites: Publication date: Jan. 1, 1993 Adult – The rhododendron borer moth has a black head with green and white markings. Monitoring. Host Plants – Rhododendron is the principal host for the rhododendron borer. The borer is pale yellow with a dark head and about ½ inch long. These pests overwinter as pupae in the soil. Rhododendron tip midge, Clinodiplosis rhododendri (Felt), Cecidomyiidae, DIPTERA. Over the last couple of weeks, there have been many reports of damaged rhododendrons. The fully grown larva is dirty white with a brown head. The pests are commonly transported in the egg stage on nursery stock. The thorax is black and blue with a broad patch of pale yellow or shiny white on each side. Rhododendron tip midge. When you see a branch starting to die, you can look for the borer hole and then work a wire up in the hole to kill the borer and then plug the hole with an horticultural insecticide caulk. Young infested leaves, usually less than 5 cm long, develop inwardly rolled margins with swollen, greenish-yellow tissue. The larvae are whi sh, hairless caterpillars with brown heads. Basically cylindrical, it is tapered at both ends, with the neck bent to one side. Lightly infested leaves have pale green bulges over most of the surface and become stunted and distorted. It’s in the spring, when many plants are breaking dormancy and putting on new growth more rapidly than we can imagine possible, that we finally see the damage that winter has done to our Rhododendron shrubs. Branches may be girdled, causing the leaves to turn yellow, then brown and die. The yellow-white larvae are caterpillars about 13 mm long. Adult – The rhododendron tip midge is a light-brown, 1.25-mm-long fly. Trunk damage caused by rhododendron borer. Areas of the bark are killed and sawdust-like castings may exude from holes. Damage: Injury caused by this key pest in ornamental plantings of rhododendron tends to increase from year to year if an infestation is not effectively managed. The abdomen is also black and blue with segments two, four, and five trimmed with yellow dorsally; segments three through six are yellowish on the underside. While some are attracted to a wide range of hosts, most attack only particular kinds of trees and shrubs. Lilac Borer Damage. Some of the preferred woody hosts include hemlock, rhododendron, and yew. The egg is approximately 0.7 mm in diameter, with a smooth, shiny surface. A. Infested branches become weakened and may break off. The females deposit a brown substance over the eggs, which hardens to form a varnish-like covering. Larvae sometimes feed initially on the bud surface, but subsequently, and typically, bore into the bud. The thorax is black and blue with a broad patch of pale yellow or shiny white on each side. Lilac Borer. This is some of the damage that concerns me with my beloved rhododendron garden. The elytra possess many rounded tubercles, each with a short seta. However, a few adults also survive the winter to feed and deposit eggs during a second season. As many as 170 eggs can be found on a single leaf. Pruning infested branches helps to control the rhododendron borer. Look for signs of stem borers on rhododendrons, azaleas, mountain laurel, and blueberries Adults feed at night and drop from the plant, feigning death when disturbed. Damage. Young infested leaves, usually less than 5 cm long, develop inwardly rolled margins with swollen, greenish-yellow tissue. Rhododendrons are not highly susceptible to insect pests, but they are occasionally beset by rhododendron borers, rhododendron lace bugs, and two kinds of weevils. For specific chemical controls, see the current state extension recommendations. When mature, the maggots drop to the soil to pupate. The borer is the immature form (caterpillar) of the rhododendron borer moth. Initially the young larvae feed on rootless; but after the third molt, the larvae move to the larger roots. Several species of clearwing and flatheaded borers can infest landscape plants. The female has broader bands on segments two, four, and five than the male does. Damage – Twigs and small branches are preferred by the rhododendron borer. Distribution – First described in 1939, this midge does not have a well-defined distribution. IPM of Midwest Landscapes 93 Pests of Trees and Shrubs Clearwing borers: maple callus borers, oak borers There is a tuft of black and yellow scales at the tip of the abdomen. Life History – These pests overwinter as pupae in the soil. If so, then your rhododendrons are suffering from thrip damage. Heavy infestations of this pest are unusual and sporadic. The rhododendron borer is found in the mountains of the Atlantic Coast states wherever rhododendron grows abundantly. Adult. E. Damage to rhododendron leaves by adult weevils. Therefore, it seems that at least two generations occur each year. Initially the young larvae feed on rootless; but after the third molt, the larvae move to the larger roots. This publication printed on: Dec. 19, 2020, The oblong black vine weevil is 10 to 11 mm long and has a short snout. But, if it is the entire shrub than it needs to dug up and disposed of. The adult flies emerge and lay eggs in the spring as new plant growth develops. Try the following methods, or contact me when you see damage and you need help gathering evidence and deciding how … They are fast and I have not yet captured them with a photo. Many herbaceous and woody plants have been listed as hosts for the black vine weevil. The insect seems to favor relatively well-lighted sites, but bushes in the shade can also be badly infested. Look above where you see the frass and you’ll find the hole where the borer pushed these deposits out of the stem. Enter your email address to subscribe to our blog and receive notifications of new posts by email. In 1979, a long single row of 'Directeur Moerlands' was examined and the larger mature plants showed signs of borer damage. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status. Pupa – The pupa is white with prominent dusky spines on the head, abdomen, and legs. It is alternately called the rhododendron stem borer, azalea stem borer, or blueberry stem borer, depending on host plant affected. In addition to rhododendrons, the stem borer, Oberea myops Haldeman, also attacks azaleas, mountain laurel, and blueberries. However, a few adults also survive the winter to feed and deposit eggs during a second season. However, if there is a hole in the stem, the borer is deeper than your cut and you’ll need to repeat your pruning lower down. The flattened maggot is whitish and about 1.27 mm long. Past infestations on older plant parts will appear as shallow, longitudinal grooves in the bark. Symptoms The rhododendron tip midge is a light-brown, 1.25-mm-long fly. A. Maggot. Asheville, NC 28806 This moth is indigenous to the United States. It is white when first deposited but becomes brown as it ages. Lightly infested leaves have pale green bulges over most of the surface and become stunted and distorted. Three weeks later, adults emerge. AG-189. 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