Balsam gall midge

Balsam gall midge - Balsam fir twig seriously damaged
  • Latin name: Paradiplosis tumifex Gagné
  • French name: Cécidomyie du sapin
  • Order: Diptera
  • Family: Cecidomyiidae
Description

Distribution

Canada

Micro-habitat(s)

Needle

Damage, symptoms and biology

Balsam gall midge damage appears on current-year needles as early as late June and persists until fall. The larvae initiate the formation of galls, which appear as swollen growths at the base of the needles; several galls can be seen on a single needle. Each gall contains a larva, which feeds on the internal tissue of the needle. Galled needles turn yellow and dry out, causing them to drop prematurely in the fall.

Repeated severe infestations can cause tree growth loss but does not result in mortality.

The appearance of the adults in May coincides with the development of fir buds. The female lays her eggs between the tight needles of the opening buds. Each newly hatched larva crawls to the base of a needle, where it settles and begins to feed, initiating the growth of gall tissue, which ultimately completely encloses the larva, thus forming the gall.

The larva leaves the gall in the fall and drops to the ground where it overwinters.

Life cycle (East of the Rockies)

Life cycle (East of the Rockies)
Stage/Month J F M A M J J A S O N D
Egg
 
Larva
 
 
Pupa
 
Adult
 

Other information

A species native to North America, the balsam gall midge occurs throughout the range of fir. In Canada, it is particularly damaging to Christmas tree plantations and in Quebec, it is monitored by the Réseau d’avertissements phytosanitaires (RAP), the province’s plant pest warning system.

The balsam gall midge was first recorded in eastern Canada in 1938 and since then, it has been regularly reported. Infestations are generally of short duration, i.e. roughly three years.

In urban environments, treatment is generally unnecessary, because after the galled needles drop in the fall, there is no visible damage the following spring. During severe outbreaks, control measures against this insect are justified only to protect the foliage of firs to be sold as Christmas trees.

Canadian Forest Service Publications

Balsam gall midge

Diet and feeding behaviour

  • Phyllophagous : Feeds on the leaves of plants.
    • Gall-forming: Induces the formation of galls and feeds on their tissues.
Information on host(s)

Main host(s)

Balsam fir

Photos
  • Balsam gall midge Lateral view of a gall on a balsam fir needle
  • Balsam gall midge Galled needles of balsam fir about to drop in the fall
  • Balsam gall midge Balsam fir needles bearing two galls; appearance of a galled needle in summer and in fall
  • Balsam gall midge Larva into its gall
  • Balsam gall midge Balsam fir twig seriously damaged
  • Balsam gall midge Two balsam fir twigs seriously damaged placed side by side to show the galls on both sides of the twig
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