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--- New PNW Extension Publication ---
Managing Russian Thistle under Conservation Tillage in Crop-Fallow Rotations

Pacific Northwest Extension bulletin PNW 492, "Managing Russian Thistle under Conservation Tillage in Crop-Fallow Rotations," was printed in November 1995. It is a full-color revision of PNW Conservation Tillage Handbook Series No. 16 in Chapter 5 that was released earlier in 1995 with a similar title. This new publication is 3-hole punched so it can also be filed in the Handbook.

The authors are: Frank Young, USDA-Agricultural Research Service research agronomist, Pullman, WA; Roger Veseth, Washington State University and University of Idaho conservation tillage specialist, Moscow, ID; Donn Thill, University of Idaho weed scientist, Moscow; William Schillinger, Washington State University area extension agronomist, Ritzville; and Dan Ball, Oregon State University weed scientist, Pendleton, OR.

Russian thistle (Salsola iberica) is a summer-annual broadleaf weed that can cause serious production problems in crop, following harvest, and during summer fallow in low-precipitation cropland areas of the Pacific Northwest. Reliance on tillage to control Russian thistle after harvest and during the summer fallow season can reduce crop residue on the soil surface and decrease surface roughness, which increases the potential for soil erosion and soil water loss by evaporation and runoff. Herbicides in the sulfonylurea family (such as Glean and Finesse) provided effective Russian thistle control in the 1980's, but widespread Russian thistle resistance to these crop protection chemicals has resulted in the need to develop other management options.

Fortunately, PNW research and the experiences of an increasing number of growers show that good Russian thistle control, effective soil conservation, and profitable farming operations are not mutually exclusive. Management strategies with improved cultural and herbicide options for Russian thistle control are providing effective weed control in profitable conservation systems. The four primary goals for Russian thistle management strategies should be to: 1) Reduce Russian thistle seed production and soil seedbank; 2) Reduce wind and water erosion potential: 3) Increase soil water storage and crop yield potential: 4) Increase profitability...the bottom line.

The publication begins with a review of Russian thistle biology as it relates to management, including seed distribution, seed dormancy and longevity in soil, seed germination and emergence, plant growth after establishment and crop competition. Considerations are also presented for managing herbicide resistance and managing wheat and Russian thistle residue to optimize water and soil conservation. Being aware of a number of important biological traits and crop production options described in the publication can help to develop effective Russian thistle management strategies. These include:

  • Short seed dormancy and longevity in the soil
  • Extensive germination period from early spring through late summer
  • Extensive flowering and seed formation period from early summer until a killing frost
  • Extensive soil water use in crop, after harvest, and in fallow
  • Lower populations, growth, and seed production in a uniform stand of winter wheat than in spring wheat
  • Reduced problems with management practices that increase crop competitiveness
  • Increased wind dispersal of seed by blowing plants with fall tillage practices that sever the plant from its roots
  • Increased soil water storage potential and reduces erosion hazard with retention of both wheat and weed residue Widespread resistance to sulfonylurea herbicides

Options for Russian thistle control are presented for each "window of opportunity" in the cropping system, including in crop, preharvest, post harvest, in summer fallow, and along field borders and roadways. The publication presents a chronological series of detailed management strategy considerations for controlling a heavy Russian thistle infestation beginning in the crop year and through two complete cycle of the crop-fallow rotation.

The 12-page bulletin is available for $2 through local county extension offices in Idaho, Oregon and Washington. It can also be ordered directly through the Publications Office at the University of Idaho Ag Communications Center (208-885-7982). Pacific Northwest Extension Weed Series bulletin PNW 461, "Russian Thistle" provides more detailed information on identification and biology of the weed. Other information sources on weed control in crop-fallow regions is "Managing Downy Brome under Conservation Tillage Systems in the Inland Northwest Crop-Fallow Region," PNW Conservation Tillage Handbook Series 15 in Chapter 5, published in June 1994. Copies of this Handbook Series publication can be requested from Roger Veseth, WSU/UI Extension Conservation Tillage Specialist at (208) 885-6386, or Don Wysocki, OSU Extension Soil Scientist at 503-278-4186.

The entire Handbook can be purchased through county extension offices for $20, including postage and handling. Everyone who purchases the Handbook (and returns the enclosed updating-card) are added to the mailing list for new Handbook Series publications and related information on conservation tillage systems. New Tables of Contents are provided periodically to include additions to the Handbook.


Contact us: Hans Kok, (208)885-5971 | Accessibility | Copyright | Policies | WebStats | STEEP Acknowledgement
Hans Kok, WSU/UI Extension Conservation Tillage Specialist, UI Ag Science 231, PO Box 442339, Moscow, ID 83844 USA
Redesigned by Leila Styer, CAHE Computer Resource Unit; Maintained by Debbie Marsh, Dept. of Crop & Soil Sciences, WSU