Do you battle garlic mustard every spring? You’ll be happy to find out that researchers are tracking an aphid that loves to feed on this invasive herb.
Garlic mustard is a herbaceous, flowering plant that smells like garlic when it’s crushed. Its seeds can be transported or blown around by vehicles and it spreads quickly, outcompeting other plants.
Researchers discovered the garlic mustard aphid in the United States in 2021. They have since confirmed populations in Connecticut, Massachusetts, Michigan, Minnesota, Ohio and Wisconsin.
More: Let’s talk about Michigan’s invasive herbs: How to identify them and the threat they pose
How to identify garlic mustard
The first year it grows, it creates heart-shaped basal rosettes (leaves) at ground level.
Long one to four-foot stems bolt up from the second-year plants. They have clusters of tiny, white four-petaled flowers. If you crush the leaves or stems, the plant smells like garlic.
This plant thrives in wooded areas and can tolerate deep shade.
Tips to identify garlic mustard:
- An herbaceous, flowering plant that smells like garlic when crushed.
- Heart-shaped basal rosettes (leaves) appear in year one at ground level.
- In the second year, stems shoot up (1-4 feet) and develop flowers and seeds.
- Leaves become more toothed and triangular in shape.
- Clusters of tiny, white, 4-petaled flowers bloom in early spring.
- Seed pods are green, long and narrow and look like stems – turning brown in fall.
Combating garlic mustard
Pulling invasive garlic mustard by hand is the most common method of control, but the plants can produce hundreds of tiny seeds that spread easily to start new patches.
Garlic mustard isn’t picky about where it grows and can survive in sun, shade, moist or dry soil. It also has allelopathy, which is the ability to release chemicals that limit or prevent the growth of other plants.
When you’re removing garlic mustard, you should double-bag all plant material and place it in sunlight for a few days so the plants decompose before you get rid of them.
Officials do not recommend composting the plant because the seeds can survive. You can click here to learn more about disposing of garlic mustard.
Meet the garlic mustard aphid
Rebecah Troutman, a natural areas biologist at Holden Forests and Gardens in Ohio, found the garlic mustard aphid for the first time in the U.S. while pulling garlic mustard in 2021.
“I did some Googling and made a preliminary identification of the garlic mustard aphid, Lipaphis alliarae,” said Troutman. “I then sent a sample to Doris Lagos-Kutz, research associate at the U.S. Department of Agriculture, who confirmed it was the first official sighting of the European aphid in the U.S.”
The garlic mustard aphid is a small, dark gray to green insect. Sometimes it’s called the “grenade” because of the pattern of raised blotches on its back. These aphids suck sap from garlic mustard plants, which cause puckered, yellowed or wilting leaves and twisted seed pods.
Troutman and Midwest Invasive Plant Network coordinator Michelle Beloskur are working to raise awareness about the garlic mustard aphid.
“Since 2021, we’ve identified isolated populations in Connecticut, Massachusetts, Michigan, Minnesota, Ohio and Wisconsin,” said Beloskur. “We’re seeing impacts like shorter plants, fewer and twisted seed pods, and less overall biomass at these sites. It appears that even a small number of aphids can affect plant growth.”
Report sightings of garlic mustard aphids
Beloskur and Troutman want to learn more about where garlic mustard aphids are and the impact they’re having.
You can help by reporting sightings of garlic mustard, garlic mustard aphids or signs of aphids on garlic mustard plants.
- Reporting sightings of garlic mustard or garlic mustard aphids online at EDDMapS.org/report or through the app. Users need to sign in. Include photos of the plants, plant damage and/or the aphids.
- If you would like to submit a sample you can email Rebecah Troutman at RTroutman@HoldenFG for instructions.