NC State Extension Publications

Description and Biology

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The rhododendron gall midge, Clinodiplosis rhododendri, seems to attack only the new growth of rhododendrons. This gall midge is light brown and very small mosquito-like fly. Males are hairy and have antennae longer than the body. Females have a short ovipositor and antennae about as long as its body. The flattened maggot is whitish and visible but very small. These pests overwinter as prepupae (a non feeding maggot stage) inside a flimsy, silk cocoon in the soil. In spring, the maggots pupate and the adult flies emerge a short time later to lay eggs as new plant growth develops. Newly hatched larvae feed within the puckered and curled leaf margins. If many larvae are found in a bud, the bud may die completely. If the buds are infested later, the new leaves curl in on the margins, and the tiny white maggots develop inside the tightly rolled plant tissue. About a week later, the maggots drop to the soil to spin their cocoons and pupate. Damage first appears in late May or early June and often reappears later with each flush of growth during the growing season. We may have three or more generations per year here in North Carolina. Heavy infestations of this pest are unusual and sporadic, but when they do occur, the gall midges can cause extensive damage.

Rhododendron gall midge maggots are small and whitish.

Rhododendron gall midge maggots are small and whitish.

Rhododendron gall midge maggots cause distored growth.

Rhododendron gall midge maggots cause distored growth.

Host Plants

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Both Rhododendron catawbiensis and R. maximum are susceptible to the rhododendron gall midge. Infested buds produce puckered, discolored leaves that may drop prematurely.

Residential Recommendation

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An effective cultural control method for homeowners is the removal and destruction of newly infested foliage. This practice may eliminate the problem within a single year or two. No chemicals are currently registered for control of rhododendron gall midges. Try Orthene or imidacloprid as a thorough spray as the new growth emerges to try to control the maggots before extensive damage is done.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: Nov. 11, 2013
Revised: Oct. 11, 2019

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