Environment

Mist flower gall fly.
Source: Landcare Research Biocontrol agents:
Mexican devil weed gall fly
Mist flower gall fly

Scientific names:
Procecidochares utilis (Mexican devil weed gall fly)
Procecidochares alani (mist flower gall fly)

Target weeds:
Mexican devil weed (Ageratina adenophora), and mist flower, (Ageratina riparia), which are very closely related and occupy similar habitats. They infest a large range of plant communities with moderate-to-high light intensity, and tolerate a wide range of conditions. Both species are often found growing together, mistflower being distinguished by narrower leaves, sharp teeth and smaller flower heads. 

What do Mexican devil weed gall fly and mist flower gall fly look like?

These two species are very similar in appearance, although each is specific to its namesake host weed.

Adult mist flower gall flies have boldly-patterned wings with a wingspan of 8mm, females being distinguished by their long, black ovipositor. This fly can complete several generations in the warmer months and has a generation time of 6-7 weeks.

What about their life cycles?

Adult females begin laying eggs in spring into the lateral growing points of the plants. Larvae, which are creamy white, burrow into the tender buds of the plant which react by producing gall tissue around the infestation. The bulbous swellings or galls increase in size and can reach 2-3cm in diameter. The pupae are brown and found within the gall, new adults emerging through a thin window in the gall formed by the larva before it pupates.

Where are they found?

Throughout Northland, with the mist flower gall fly being harder to find now that mist flower is controlled by the mist flower fungus.

When and how are they best harvested for redistribution?

Collect at least 100 large mature galls (without emergence holes) in late summer and autumn and leave on the ground at new sites.