1 4 B A R N Y A R D S & B A C K Y A R D S
Y
es, the rumors are true. After several years of
consideration by the Wyoming Weed and Pest
Council, Russian olive was recently placed on the
state’s designated noxious weed list.
What does this mean for Wyoming citizens? The
legal ramifications are primarily twofold.
First, under Wyoming’s nursery stock laws,
sales of Russian olive seeds, rootstocks, cuttings for
propagation, and live trees are now banned within
the state. The Wyoming Department of Agriculture
is responsible for enforcing this during its annual
nursery stock dealer inspections.
Second, each county weed and pest control
district is required by law to implement a Russian
olive control program. Most districts have prioritized
control efforts to focus on Russian olive that has
escaped cultivation and invaded pasture and riparian
areas. Whether any action would be taken to remove
or control Russian olive trees that seem likely to
spread is up to each county’s weed and pest control
district. Its invasion and negative impacts are widely
seen in many areas of Wyoming including, but not
limited to, the Big Horn Basin, along the North Platte
River, and many parts of the Powder River Basin.
Many folks are still wondering why the trees,
which were promoted for windbreaks and wildlife
habitat for so many years, are now on Wyoming’s
hit list. While Russian olive does provide a rapidly
growing, drought-tolerant windbreak, it often refuses
to leave well enough alone and stay where it is
planted. Mature trees produce enormous numbers
of fleshy fruits every summer that are consumed
by many wildlife species, including deer, turkeys,
raccoons, coyotes, and numerous birds. Seeds
within the eaten fruits are then widely dispersed.
Russian olive seeds are capable of establishing and
growing across a broad range of conditions while
native riparian trees, such as cottonwoods, have very
specific requirements for establishment.
RUSSIAN OLIVE
IS
really a noxious weed in Wyoming
?
S U M M E R 2 0 0 7 15
This, coupled with other factors such as drought,
beaver preference for native trees, and intense
competition for light, water, and nutrients, is resulting
in Russian olives displacing cottonwood and willow
stands.
Russian olive-dominated riparian areas are often
much less diverse in terms of habitat structure and
plant community composition. Despite the use of the
fruits by many animals, this reduced habitat diversity
can negatively impact other wildlife, such as cavity
nesting and insect eating birds. Little is still known
about the potential full impacts of Russian olive’s
domination of riparian areas.
Here are a few recommendations for controlling
Russian olives. Cutting alone is not enough to control
this tree. Russian olive is a vigorous resprouter from
the root crown and will rapidly regrow following
cutting or any type of top growth damage. To reduce
resprouting, apply herbicide directly to the stump
within 15 minutes after cutting (the sooner the
better). Effective cut-stump herbicide treatments
include triclopyr, imazapyr, and glyphosate.
Foliar herbicide applications are difficult to make
on large trees, but small trees and resprouts may
be controlled with 2,4-D. Late summer timings are
very effective. For more detailed information, contact
a county weed and pest control district. Wyoming
weed and pest control district information is available
at www.wyoweed.org/wp_dist.html.
Small seedlings may also be hand pulled in
the spring and early summer, but this is extremely
difficult when stems are greater than one-half inch in
diameter. Resprouts from older root crowns cannot
be hand pulled at all. In addition to the sprouts,
control efforts will need to continue until the seed
source within the soil is exhausted, which may take
several years.
Contact a local University of Wyoming
Cooperative Extension Service or weed and pest
control district office for more information on control
programs for Russian olive. County CES office
information is available at http://ces.uwyo.edu/
Counties.asp.
Russian olive is not the first popular horticultural
species to be placed on Wyoming’s noxious
weed list. Yellow toadflax, common tansy, purple
loosestrife, and saltcedar (Tamarix) have all escaped
cultivation and have become a serious threat to
Wyoming ecosystems. Unfortunately, desirable
characteristics of some horticultural species can
cause them to become invasive.
Only a few horticultural plants have escaped to
become pests in natural ecosystems. Unfortunately,
Russian olive is one that has.
Stephen Enloe is a weed specialist with the University of Wyoming Cooperative Extension Service. He can be
reached at (307) 766-3113 or [email protected]. Slade Franklin is the state weed and pest coordinator with
the Wyoming Department of Agriculture and can be reached at (307) 777-6585 or [email protected]
Russian olive produces numerous seeds, which are eaten
by many wildlife species and are then widely dispersed.
