VALUE AND USE
SPECIES: Ambrosia psilostachya | Western Ragweed 



WOOD PRODUCTS VALUE : 
NO-ENTRY


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Managers rate the forage value of western ragweed as fair [121].  The
foliage and stems contain cinnamic acid and sesquiterpene lactones that
deter herbivory [129].  However, western ragweed is not considered a
poisonous plant [88].  It is moderately important as ungulate forage
[24,31,48,98,103].  Western ragweed is used for food and nesting
material, and as a habitat component by small mammals and nongame birds
[10,52,63].  Western ragweed is an important food (seeds and foliage) on
activity sites for upland gamebirds [11,73,110,123].  In a study of the
relationship of grasshoppers to different pasture treatments and range
sites in Kansas tallgrass paririe, western ragweed was one of the two
most abundantly available and most ingested forbs [78].


PALATABILITY : 
Ragweeds are normally considered to be unpalatable but when treated with
2,4-D become palatable.  Treated plants may, however, accumulate
nitrates to a toxic level [76].  In Montana, Utah, and Wyoming, western
ragweed palatability is poor for ungulates and waterfowl.  Its
palatibility has mixed ratings for the following species:

                           MT      UT      WY
    Small mammals                 Poor    Good
    Small nongame birds   Good    Poor    Good
    Upland game birds     Fair    Poor    Fair


NUTRITIONAL VALUE : 
Mature western ragweed seeds from an eastern Texas prairie contained 1
to 3 percent silica, which reduces digestibility; the seeds had 70 to
less than 90 percent dry matter digestibility [109].  However, the seeds
contained more than 25 percent protein.  Forage quality (seasonal crude
protein content and digestibility) of western ragweed on a Texas range
was higher after spring burning [17].


COVER VALUE : 
The degree to which western ragweed provides environmental protection
during one or more seasons for wildlife species is as follows:

                                MT      UT      WY
        Pronghorn              ----    Poor    Poor
        Elk                    ----    Poor    Poor
        Mule deer              ----    Poor    Poor
        White-tailed deer      ----    ----    Poor
        Small mammals          Poor    Fair    Poor
        Small nongame birds    Poor    Fair    Poor
        Upland game birds      ----    Poor    Poor
        Waterfowl              ----    Poor    Poor


VALUE FOR REHABILITATION OF DISTURBED SITES : 
Although western ragweed readily invades disturbed ground and is not
considered desirable forage, it is a native forb and is included in
prairie restoration plantings.  Adequate seedbed preparation is
important for successful plant establishment [37,117].  Western ragseed
was seeded for tallgrass prairie restoration in north-central Missouri
at 0.08 pounds bulk per acre (91 g bulk/ha) with a rangeland drill
[117].  In the reclamation of a sand and gravel pit in Ohio, western
ragweed was hydroseeded with native grasses; seeds were covered with
less than 0.5 inch (1 cm) of soil [37].  Western ragweed has established
on artificial levees made to reclaim marshland along the lower
Sacramento River in California [127].

Established western ragweed may have to be controlled when planting
other native species in an area.  For example, when fourwing saltbush
(Atriplex canescens) was planted on shrublands in Texas, western ragweed
was controlled with herbicides [95].


OTHER USES AND VALUES : 
Western ragweed was used for medicinal purposes by American Indians.
Pueblo women in New Mexico drank a tea made from western ragweed during
difficult labors at childbirth, and the Cheyenne of the Central Plains
used it to treat intestinal problems and colds [12].  Kiowa of Oklahoma
rubbed a preparation of western ragweed on the sores of humans and
horses [12].


MANAGEMENT CONSIDERATIONS : 
Western ragweed is one of the main hay-fever plants in late summer when
it is in bloom [70,74,130].

Western ragweed is a major invader of deteriorating rangeland.  It
readily moves into open habitat in prairies [19,121].  Western ragweed
is not drought resistant.  It was partially or totally eliminated from
mixed-grass prairies during the drought of the 1930s; however, western
ragweed recovered by the mid-1940s [40,121].

Livestock:  Western ragweed averaged 1,200 pounds of dry matter per acre
(1,342 kg/ha) on a clay upland range site near Hays, Kansas, and was
beneficial to grass production [83].  Grass yields were never less than
2,000 pounds per acre (2,237 kg/ha) from sites that produced 7,000
pounds per acre (7,830 kg/ha) western ragweed [83].  A buildup of 3 to 5
inches (8-13 cm) of grass mulch on a lightly grazed rangeland delayed
western ragweed growth in the spring; however, litter increased the
moisture supply [71,122].

For optimum use of western ragweed on shortgrass rangeland, continuous
season-long or year-long grazing at moderate stocking rates, combined
with spring burning, is recommended [83].  Launchbaugh and Owensby [83]
recommend grazing western ragweed early in the growing season.  Range
cattle consume western ragweed by choice most heavily in April [48].

Western ragweed cover increases when it is grazed or disced
[44,57,94,123].  There was no significant (P>0.05) difference in
relative abundance of western ragweed under moderate or heavy stocking
rates [67,69].  However, western ragweed cover was significantly greater
on continuously grazed pasture compared with short duration grazing
[31,45].  Western ragweed herbage was significantly higher under thinned
ponderosa pine compared to unthinned areas [28].  Herbage production of
western ragweed decreased as the depth of humus, duff, and litter
increased under ponderosa pine canopies [29].

Chemical Control:  Herbicide should be applied to western ragweed during
the late vegetative stage before the formation of flowerbuds; western
ragweed is moderately or totally resistant during other growth phases
[93,111].  Before flowering, it is susceptible and may be controlled
with one foliage spray application at 1 pound active ingredient per acre
(1.1 kg ai/ha) for 2,4-D, 2,4,5-T, Silvex, 2,4,-D-B or 0.25 pound active
ingredient per acre (0.28 kg ai/a) Grazon PC and Banvel [43,83,93].
Grazon P + D will give control for more than 1 year [43].

Western ragweed root exudate significantly inhibited the formation of
nodules on legume roots, which decreases their ability to fix nitrogen
[128].

Western ragweed repsonds differently to different combinations of
disturbance and burning.  Western ragweed occurred significantly more on
unburned pocket gopher mounds than on burned; it occurred less
frequently on ant hills than on controls [55].  Western ragweed had
significantly higher average cover on burned areas immediately outside
of buffalo wallows compared to unburned controls [36].

Related categories for Species: Ambrosia psilostachya | Western Ragweed