Leaf galls on Populus tremula are induced by several gall midge species (Diptera: Cecidomyiidae) and some aphids (Hemiptera: Aphididae), and stem galls by at least one beetle species. Some common eriophyid mite galls are also shown below, although mites are not insects but arachnids.

Gall midges (Diptera: Cecidomyiidae)

Contarinia petioli

(Diptera: Cecidomyiidae)

A common gall midge on Populus tremula. Galls are usually located singly on petioles, but sometimes they are clustered and they may even occur on current-year shoots. Each gall contains a single yellowish larva, which exits the gall in the autumn to pupate on the ground.


Galls of Contarinia petioli on Populus tremula.

Galls of Contarinia petioli on Populus tremula.

Dasineura populeti

(Diptera: Cecidomyiidae)

Oviposition by Dasineura populeti causes an abnormal growth response in aspen leaves, which leads to the formation of upward-curled rolls on the leaf edges. Each roll houses numerous small whitish midge larvae. The rolls resemble shelters constructed mechanically by some beetle and moth species (click here to see examples of other rolls).


Leaf roll induced by Dasineura populeti on Populus tremula.

The leaf rolls may be induced on both sides of the leaf blade.

Harmandia tremulae

(Diptera: Cecidomyiidae)

Harmandia gall midges induce globular galls on Populus tremula. Two species, H. tremulae and H. globuli, cause reddish galls on the upper surfaces of the leaves. The galls are usually located adjacent to larger leaf veins (left). Each gall contains a single orange midge larva that has no visible legs nor head (right).


Harmandia tremulae galls on Populus tremula.

Larva of Harmandia tremulae inside opened gall. The galls of H. globuli have thinner but harder walls.

Harmandia sp.

(Diptera: Cecidomyiidae)

Galls of either Harmandia tremulae (= loewi) or H. globuli.


Harmandia sp. galls on Populus tremula.

Harmandia cavernosa

(Diptera: Cecidomyiidae)

Harmandia cavernosa also induces roundish leaf galls on aspen, but in contrast to the two aforementioned Harmandia species, the galls of H. cavernosa project more towards the lower side of the leaf. The galls are typically attached to the main leaf veins, and about two thirds of the gall is on the underside of the leaf blade. When the larva is full-grown, a slit opens on the top of the gall, and the larva exits the gall to pupate on the ground.


Galls of Harmandia cavernosa on leaves of Populus tremula.

Gall of Harmandia cavernosa on Populus tremula. Note that the main part of the gall is situated under the leaf blade.

Aphid galls (Hemiptera: Aphididae)

Unidentified aphid gall

(Hemiptera: Aphididae)


This is a big open leaf gall which occurs commonly on aspen, but whether it is actually caused by the aphids is still a bit unclear.


Unidentified aphid gall on Populus tremula.

Mass of unidentified aphids inside the Populus tremula leaf gall shown in the picture to the left.

Mite galls (Acari: Eriophyidae)

Mites are arachnids, not insects, but these common species are included here because their galls resemble insect galls.

Eriophyes diversipunctatus

(Acari: Eriophyidae)

This eriophyid mite causes paired red swellings at the point at which the petiole joins the leaf blade. The tiny mites live inside the small galls.


Galls of Eriophyes diversipunctatus on Populus tremula.

Galls of Eriophyes diversipunctatus on Populus tremula.

Aceria varia

(Acari: Eriophyidae)

The eriophyid mite Aceria varia induces red  or brown spot-like deformations on the upper surface of Populus tremula leaves. The mites themselves are very small and live among short hairs that form the spots. The species is  common and often occurs together with Phyllocoptes populi (below).


Galls of Aceria varia on the upper surface of a Populus tremula leaf.

Close-up of Aceria varia galls on Populus tremula. Note the grainy appearance.

Phyllocoptes populi

(Acari: Eriophyidae)

This common mite species also causes spot-like deformations on aspen leaves, but the galls are located on the lower surface of the leaf. The tiny mites live among short hairs that protrude from the shallow "cups" on the leaves.


Galls induced by Phyllocoptes populi are small pale swellings on the upper surface of the leaf. By contrast, Aceria varia galls (the one on the lower right-hand side of this leaf) are reddish-brown and hairy on the upper surface, and the "cup" projects downwards.

Same leaf seen from the underside, on which the Phyllocoptes populi galls are seen as hairy pale areas, whereas the Aceria varia gall forms an elevated spot on the lower left-hand side of the leaf.

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