New Colorado Research Advances Use of Fungus Against Canada Thistle

Farmers now have a new option to control weed menace.

Published on: Jan 27, 2014

Growers in Colorado who would like to find a new way to control Canada thistle just may have their wish granted.

New Colorado Department of Agriculture work on the weed shows that using a special fungus which only attacks the plant can kill the invasive species right down to the root.

The USDA funded project involves introduction of the fungus to weed patches, explains CDA's Dan Bean, Biological Pest Control director. His project consists of finding the fungus and distributing it to patches of Canada thistle.

"Timing is everything with the project," he says. "The initial survey of thistle patches for naturally occurring rust (fungus) must happen in the spring when infected plants are visible, while teliospores only appear and can be harvested in the summer."

New Colorado Research Advances Use of Fungus Against Canada Thistle
New Colorado Research Advances Use of Fungus Against Canada Thistle

Infection of rust-free Canada thistle patches  using the teliospores is possible in the late summer and fall, when new and susceptible foliage begins to grow from the root system, he explains.

Involved in this war is the fungus Puccinia punctiformis and the targeted enemy, Canada thistle that has raided across more than 400,000 acres of Colorado range, pasture, and crop land as one of the top most wanted weeds, according to Bean.

The dread weed may meet its end once the fungi find their way to infested land, since the thistle – the only plant the Puccinia attacks – will drain the life out of the invader.

High concern over the weed's track record of spreading  has triggered a  new agreement between the USDA and CDA to tackle the weed with the rust fungus.

What Bean is doing involves spreading the fungi among thistles and observing the impact. A $392,000 four-year USDA grant to CDA will fund work

While the fungus is already found in Colorado, it isn't always where the thistles are, and since the Puccinia spread is slow and sporadic, Bean is helping it along by introducing it to patches of thistle throughout the state.