Gall midges hoping to help clean 
up noxious weeds in Clifton area 


KAREN ROSEN/Palisade Insectary These tiny gall midges are being used to battle Russian knapweed, a noxious weed poisonous to livestock and tough to kill.



Some new residents moved into a little weed-infested plot in Clifton this week. Their names are Jaapiella ivannikovi and they’re gonna clean up the neighborhood because they have a job to do in the war on weeds.

More commonly known as the gall midge, this miniscule fly is the latest tool in the battle against Russian knapweed, a dangerous noxious weed that is poisonous to livestock and difficult to vanquish.

Officials with the Palisade Insectary and Mesa County helped establish the insect in a particularly infested area of knapweed near the Clifton Sanitation District by planting knapweed already occupied by the insect in the midst of the patch of weeds.

Palisade Insectary biocontrol specialists Karen Rosen, Sonya Ortega and Nina Louden carefully introduced the midges to their new habitat, watering the knapweed to ensure it would be a good home for the insect until it moved on to others in the area.

“We have lots of food for them here,” said Travis Haldemann, Mesa County parks crew leader.

This particular patch of Russian knapweed has been on the radar for Melissa Werkmeister, Mesa County’s weed and pest coordinator.

“I want to keep it from spreading further,” Werkmeister said. “What we’ll probably see is a patchwork of affected knapweed that keeps them from producing more seeds and spreading even more.”

That’s where this amazing insect comes in. The adult midge emerges from the gall, mates and then lays microscopic eggs on the tender leaf tips at the top of the plant. Five to seven days later, those eggs hatch, and the larvae begins to feed on the leaves. This damage causes the plant to produce the galls around the larvae.

This cycle happens about once a month, according to Rosen. The insects have proven that they can overwinter in our harsh climate, and produce multiple generations of flies per season.

“It should prevent the knapweed from flowering and decrease its growth,” Louden said. “We’re still learning how it works and will continue to study it.”
The knapweed will likely still spread through its extensive root system, but officials will be studying how the midge can slow the knapweed’s progress.

When dealing with non-native invasive species such as tamarisk or Russian knapweed, experts look to their native homelands to find a natural predator. Since the weed originated in Eurasia, the gall midges also came from that region, and were established at the insectary in 2011, after overwintering.

The process for gaining approval for new biocontrol agents is lengthy and comprehensive. Officials must prove through a series of studies and quarantines that the insects will only feed on the plants intended to be controlled, as no one wants to introduce another species without a natural predator that could cause further problems.

“In the insect world, we have generalists and we have specialists,” said Ortega, explaining how scientists work to find insects that are host-specific. “We want specialists to deal with these invasive species.”

Last year was the first year insectary officials were able to recover galls produced by the flies in field studies and use those galls to help spread the fly. Louden said the plan is to monitor the site, collect the galls and redistribute the insects to other knapweed-infested areas in the state.

Erin McIntyre is an advanced master gardener, writer and Grand Valley native. Please email her at .(JavaScript must be enabled to view this email address) with story ideas or feedback.


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