Killing Imported Tumbleweeds With Imported Fungus

Outside of the cowboy hat and the longhorn steer, there’s no greater symbol of America’s Old West than the tumbleweed. Surprisingly, like the hat and the cattle, the tumbleweed is not native to the U.S.

While its rolling image across the dusty plain seems idyllic, the tumbleweed is actually a nuisance plant (Russian thistle or Salsola tragus), brought here accidentally in a shipment of flax seed from Russia (pre-Putin), that destroys crops and creates fire hazards when piles form near flammable structures. If America didn’t create it, it can at least destroy it, right? Wrong!

In the 1990s, plant pathologists in Hungary discovered a fungus that killed local tumbleweeds and sent a sample to the Agricultural Research Service's Foreign Disease-Weed Science Research Unit in Fort Detrick, Maryland. That fungus, Colletotrichum salsolae, has been tested ever since and is finally ready to be approved for release against the killer tumbleweeds.

The Agricultural Research Service released a report about a recent test in Greece where the fungus was released in a field infested with tumbleweed and the plant was eradicated in two years. The fungus works by attacking tumbleweed saplings before they have a chance to grow into the giant round bushes that dry out, snap off and roll away to spread their seeds.

As with introducing any foreign agent to kill a pest, the researchers tested to make sure that the fungus didn’t harm native plants or humans. Humans are safe. They found that only a few species were vulnerable and the infection was minor. Also, they found no plants in the U.S. that shared the tumbleweed’s genus.

If it’s approved, C. salsolae will be placed in sterilized rice and spread on tumbleweed-infested fields. Rain and nature will do the rest.

Will C. salsolae work or create a bigger invasive species problem than the tumbleweeds themselves? Only time will tell.