Glyphosate-Resistant Russian Thistle (Tumbleweed) Confirmed In Montana

[hatrack]

BOZEMAN – This article highlights the evolution of glyphosate (Roundup, RT3, and other generics)-resistant Russian thistle in Montana. Russian thistle (Salsola tragus L.), a native of southeastern Russia, is one of the most problematic broadleaf weed species in the dryland no-till cropping systems of Montana and the U.S. Great Plains. It is a summer annual weed belonging to the goosefoot family that reproduces by seed. Russian thistle commonly invades dryland crop production fields, irrigation canals, roadsides, railroads, ditch banks and other disturbed non-cropland areas in this region. It is known to reduce crop yields, hinder harvest operations and pose problems in summer fallow.

Russian thistle exhibits low seed dormancy and persistence in the soil seedbank. Seeds can germinate early in the spring, and seedlings can exhibit an extended period of emergence during the summer. Russian thistle plants are round in shape with a bushy appearance and can grow up to 4 feet tall. It has a deep tap root system that can extend up to 5 feet depth in the soil. Leaves are alternate and linear in shape. In general, Russian thistle exhibits indeterminate flowering that normally starts during mid-summer. At maturity, Russian thistle plants break off at the ground level and tumble with the prevailing wind, dispersing seeds to a long distance. A single mature plant can produce almost 250,000 seeds.

In the fall 2015, seeds of a Russian thistle population surviving glyphosate applications were collected from a chem-fallow field in Chouteau County, Montana. The field was under wheat-fallow rotation and had a history of repeated glyphosate applications. Almost 100 plants screened from the population survived the field-use rate of glyphosate (@32 fl oz/a of 4.5 lb ae/gal Roundup Powermax). Dose-response experiments conducted by Prashant Jha and Vipan Kumar, weed researchers at the MSU Southern Agricultural Research Center in Huntley, showed up to 4.5-fold levels of resistance to glyphosate. Furthermore, “the confirmed glyphosate-resistant Russian thistle biotype survived two times the field-use-rate (1 oz/acre) of Ally Extra (Group 2, Sulfonylurea herbicide), confirming multiple resistance to glyphosate and sulfonylurea herbicides,” said Kumar. The demographic spread of glyphosate-resistant Russian thistle in Montana is unknown, and the underlying mechanism(s) of glyphosate resistance is under investigation at the MSU Southern Agricultural Research Center in Huntley.

“This report confirms the first case of evolution of glyphosate-resistant Russian thistle. In Montana, this is third weed species (after kochia and marestail) that has developed resistance to glyphosate. The discovery of glyphosate resistance in Russian thistle is a concern for Montana producers,” said Jha.

EDIT

http://www.agweek.com/news/montana/3979594-glyphosate-resistant-russian-thistle-found-montana

[WhiteTara]

1. I wonder if it came in as an ornamental.

250,000 seeds from one plant is a nightmare.

[hatrack]

3. It was an accident, IIRC

There were some thistle seeds in hard red winter wheat brought by Ukrainian immigrants to the High Plains.

The rest, as they say, is history.

[WhiteTara]

4. oh. thanks

[lapfog_1]

2. my high school friend did his PhD on Russian Thistle

It is indeed a serious threat to wheat and corn crops and to grazing land.

That a new variety has shown up that is resistant to pesticides should be worrisome to farmers and ranchers across the midwest and western US...

[hunter]

5. That'll be fun on the hobby ranches.

In the 'sixties tumbleweed was everywhere in Southern California. People would make tumbleweed "snowmen." We were allowed to kill tumbleweed with fire on days it wasn't windy and dry. On the dry windy days the rolling burning tumbleweeds would spread fire.

Then for awhile tumbleweed seemed to be contained, probably by extensive use of Roundup.

These "miracles" of chemistry always work like that. The same has happened with antibiotics. Penicillin isn't the wonder medicine it used to be.

[NickB79]

6. We have a few options here

1) Forgo no-till and start cultivating between rows multiple times per season to kill the thistles before they seed. Downside: massive increase in fuel consumption, labor and soil erosion. Might recreate the Dust Bowl era.

2) Start using older, more toxic herbicides. Downside: more toxic herbicides in the ecosystem.

3) Stop farming these areas, allow them to revert to native grasslands complete with annual wildfires, and graze cattle and bison on it again. Downside: less grain production.

I vote for #3. We will be abandoning crop farming in much of the Great Plains anyway as rainfall patterns shift from climate change and the Ogallala Aquifer dries out, so we might as well do it sooner rather than later. And restoring the Great Plains ecosystem would sequester massive amounts of carbon into the soil.