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.
