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Gall Fly Produces Goldenrod Galls

Gall Fly Produces Goldenrod Galls

Gall Fly Produces Goldenrod Galls

The Canadian goldenrod and a few additional goldenrod varieties are host plants to gall fly larva. The Gall fly produces goldenrod galls which become the food source of gall fly larva over the course of the winter.  The insect has a fairly interesting lifecycle.

Goldenrod Gall

Gall Fly larva that already has their escape hole for spring.

Gall Fly produces goldenrod galls which are the large bulbs you see on stalks in the autumn and winter months on a variety of goldenrod plants.  Did you know that a fly produces those swollen bulb looking formations?

Those Large Plants on Goldenrod Stalks Are Insect Homes



Gall Fly

Gall Fly also is known as the goldenrod ball gallmaker.

Gall Fly also is known as the goldenrod ball gallmaker, is a species of fly native to North America. The species is best known for the characteristic galls it forms on several species of goldenrod plants.

Gall Flies Sole Job is Mating

Gall flies are only alive for two weeks and the entire time they are alive, they mate.  They fly around and their sole job is to mate.

A New Life Begins

The female will deposit the eggs on goldenrod in mid-spring, after 7 days the egg hatches and the larva goes to work eating and eating.  At some point, the larva will migrate to an area below the plant’s developing buds and introduce a chemical that will cause it to develop a hard bulb plant growth. The larvae bore into the plant tissue and create a large chamber. This growth will become a larva’s home from this spring to the following spring.


Inside Goldenrod Gall

Inside look at a goldenrod gall with the larva on the right side.

Interesting Little Fact

The gall fly larvae know that the galls will serve as both their homes for protection from the elements and also their winter food source.  In late September or early October, the larvae will create a small tunnel to the outside of the bulb.  This serves as the escape the following spring.  In the larvae stage, they have chewing mouths, after they molt into a fly in the spring they do not. 

Insect Preditors to the Gall Fly Larva

2 types of parasitic wasp  (Eurytoma obtusiventris & E. gigantea)
Beetle larva (Mordellistena unicolor)

During the growth stage and before winter sets in, two types of parasitic wasps and also a beetle larva will try and prey on gall fly larva.

Golden Rod to Gall Fly

Bird Preditors of the Gall Fly Larva

In late fall and throughout the winter months, the downy woodpeckers and chickadees begin searching galls for exit tunnels for easy meals.  If a bird finds a tunnel they begin to extract the larva.



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Inside Gall: SriMesh   Gall Fly:Pavel Kirillov 

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