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Goldenrod Bunch Gall Midge

Rhopalomyia solidaginis[6]

The goldenrod bunch gall midge is a fly in the gall midge family (Cecidomyiidae) that causes the growing tip of a goldenrod stem to form a tight, rosette-like bunch of leaves. Ecologists study it as an ecosystem engineer: its bunch galls give shelter and food to other arthropods, and the mix of species on a goldenrod changes when a gall is present.[1][3][2]

Group
Insect
Order
Diptera
Family
Cecidomyiidae
US records
29 states
Sources
6 cited
Updated
2026-11-09
Goldenrod bunch gall, a tight rosette of leaves at the tip of a goldenrod stem, beside a flowering goldenrod
Goldenrod bunch gall, a tight rosette of leaves at the tip of a goldenrod stem, beside a flowering goldenrod. Photo: Glenn Berry, public domain (CC0), via iNaturalist
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Look for the gall rather than the insect: a closely bunched, rosette-like cluster of leaves at the very tip of a goldenrod stem, in the terminal bud.[1][3]
  • The gall contains larval chambers; researchers studying it measure gall biomass, the number of larval chambers and their volume.[5]
  • UW-Madison Extension describes the gall on Canada goldenrod. The research cited here was all done on tall goldenrod (Solidago altissima).[1][2][3][4][5]

Look-alikes

Look-alikeHow to tell them apart
Goldenrod gall flyMakes a round swelling on the stem instead of a leafy rosette at the tip.[1]
Goldenrod gall moth (Gnorimoschema gallesolidaginis)Makes a spindle-shaped or elliptical gall on the stem rather than a bunch of leaves at the tip.[1]

Where it lives

In a survey of tall goldenrod across a 2,300 km north-south transect in the eastern United States, the galls were densest at middle latitudes. Studies cited here were carried out in old fields and at Michigan's Kellogg Biological Station.[3][2][5]

US map: public records from 29 states since 1990 (GBIF).

Biology and life cycle

It attacks the tip of the goldenrod stem, and its gall forms in the terminal bud.[1][4]

Some goldenrod plants have 'candy-cane' stems that nod at the tip while growing, a genetically controlled trait. Nodding happens during the egg-laying period of tip-attacking insects, and in a common-garden study candy-cane stems were galled only half as often as erect stems.[4]

Host-plant genetics strongly shapes gall numbers: goldenrod genotype was the best predictor of gall density and size within a year, and plots with more goldenrod genotypes held more galls. Gall density also swung several fold from year to year.[2][3]

Removing other plant-feeding insects from goldenrod led to more and larger galls. Adding soil nutrients over four years did not change gall density, though galls were smaller where carbon was added.[3]

Bunch galls work as shelter and food for other small animals: plants with bunch galls carried more arthropod species, with a different mix of species, than plants without.[2][3]

Damage and signs

  • The gall forms in the stem's terminal bud. In a Michigan field experiment, galled tall goldenrod plants were 7.1 cm shorter than ungalled ones under normal conditions (though not under experimental warming), and galled plants under drought were the least likely to produce seed.[1][5]

Health risk

None of the sources mentions any bite, sting or other risk to people.[1][2][3][4][5]

Control

Prevention

None of the sources recommends any control. Ecologists describe the midge as an ecosystem engineer whose galls provide shelter and food for other arthropods.[1][2][3]

Common questions

What are the leafy rosettes at the tops of my goldenrod?
They may be galls of the goldenrod bunch gall midge, which make the stem tip form a closely bunched, rosette-like cluster of leaves.[1][3]
Do bunch galls hurt goldenrod?
They can stunt the plant: in a Michigan study galled plants were 7.1 cm shorter, and galled plants under drought were the least likely to set seed. None of the sources treats the midge as a pest.[5][1]
Why are some goldenrod stems bent like a candy cane?
Some goldenrods have stems that nod at the tip while growing. Researchers found that this habit coincides with the egg-laying season of tip-attacking insects, and nodding stems were galled by the bunch gall midge only half as often as erect stems.[4]

Sources

  1. University of Wisconsin-Madison Extension, Wisconsin Horticulture, “Goldenrod Gall Fly, Eurosta solidaginis (Susan Mahr).” hort.extension.wisc.edu/articles/goldenrod-gall-fly-eurosta-solidagnis/ (accessed 2026-11-09)
  2. Ecology (via NCBI PubMed), “Host-plant genotypic diversity mediates the distribution of an ecosystem engineer (K. M. Crawford, G. M. Crutsinger and N. J. Sanders; Ecology 88(8): 2114-2120, 2007; abstract).” pubmed.ncbi.nlm.nih.gov/17824442/ (accessed 2026-11-09)
  3. PeerJ (via NCBI PubMed), “Local and latitudinal variation in abundance: the mechanisms shaping the distribution of an ecosystem engineer (G. M. Crutsinger, A. L. Gonzalez, K. M. Crawford and N. J. Sanders; PeerJ 1: e100, 2013; abstract).” pubmed.ncbi.nlm.nih.gov/23862102/ (accessed 2026-11-09)
  4. Ecology (via NCBI PubMed), “Ducking as a means of resistance to herbivory in tall goldenrod, Solidago altissima (M. J. Wise and W. G. Abrahamson; Ecology 89(12): 3275-3281, 2008; abstract).” pubmed.ncbi.nlm.nih.gov/19137934/ (accessed 2026-11-09)
  5. Oecologia (via NCBI PubMed), “Climate warming and drought modify galling effects on tall goldenrod (E. G. Parker et al.; Oecologia 208(4): 51, 2026; abstract).” pubmed.ncbi.nlm.nih.gov/41933258/ (accessed 2026-11-09)
  6. iNaturalist, “Rhopalomyia solidaginis taxon page (order and family).” www.inaturalist.org/taxa/325437 (accessed 2026-11-09)

Updated 2026-11-09. Built from sourced records. Spot an error? Tell us.