War on Weeds — Weeds are Everybody’s Problem

Russian Thistle

Russian thistle (Salsola tragus L.) is a prickly annual weed native to Northern Africa and Asia. It was introduced into North America in the 1870’s as a contaminate in seed. It has an extremely efficient taproot, allowing this weed to thrive in dry conditions. It invades rights-of-way, cereal grain production systems, rangeland, as well as other disturbed sites. When mature, the stem breaks off and the plant tumbles along the landscape spreading seed as it goes. While it can be utilized by livestock early in the spring before sharp pointed leaves mature or after winter moisture softens plant material, it is not the ideal forage.

Russian thistle grows 1 to 3 feet tall, is round in shape and has highly branched stems. Stems often exhibit purple-red vertical striping. Leaves are small, narrow, linear and spined at the tip. Plants are succulent when young, but as they mature, they become rigid and stiff. Russian thistle is a prolific seed producer, it can produce 4,500-150,000 seeds per plant depending on growing conditions and competition. Luckily seeds usually only remain viable for one year. One characteristic that makes it extremely successful is its ability to germinate very quickly and with little moisture.

Integrated Pest Management (IPM) options

• Prevention — Learn to identify this plant. Always plant clean seed. Clean equipment, recreational vehicles, and clothing after leaving invested areas.
• Mechanical — Hand digging or pulling can be effective on small infestations. Mowing is not a good option; plants can adapt to mowing by producing seed low to the ground.
• Cultural — Maintain a healthy stand of beneficial plants that will compete for essential resources.
• Chemical — Unfortunately, Russian thistle has become resistant to several herbicides. It is extremely important to rotate herbicide chemistries, use the correct rate and look for/remove resistant plants. Always read and follow herbicide label direction.

Idaho is a wonderful place with awesome natural resources, landscapes, agriculture and recreational opportunities. Weeds threaten all the things that we love about Idaho. To detect, contain and control weeds in Idaho we have declared “War on Weeds.” These short articles are designed to give a brief description of each species, an explanation about why it’s a problem, insights into identification and Integrated Pest Management control options. — Justin Hatch

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• Russian thistle, 10-19