The Montana Department of Transportation funds six K-12 school systems that are either growing, or are planning to grow insectaries that will cultivate insects used to kill spotted knapweed.

Boxing Knapweed

The Montana Department of Transportation wants to take a new approach
to help knock out spotted knapweed with a one-two punch.

Currently, MDT is helping fund six K-12 school systems that are either
growing, or are planning to grow insectaries that will cultivate
insects used to kill spotted knapweed. Students will hand harvest the
insects and release them onto MDT’s right-of-ways and neighboring lands
that are infected by this noxious weed.

According to Dan Williams, MDT maintenance division, many landowners
are jumping at the opportunity for students to release the insects
adjacent to their property. The insects are host specific and feed
solely on spotted knapweed.

MDT has obligated $35,000 to their biological program to purchase and
release the insects within select counties, as well as develop the
insectaries located at each school.

The school systems currently involved are Bonner Junior High, Darby
Public Schools, Noxon Public Schools, Eureka County Public Schools,
Victor High Schools, and Whitehall High School. A seventh school in
Seeley Lake is also looking to join the fight. MDT is funding each
program with $2,500 each year, for two years. Whitehall’s program
includes a training program for educators and therefore is receiving
$5,000 each year, for two years.

"We are attacking knapweed through air strikes and ground strikes,"
said Williams.

The schools are using root boring weevils and seed head moths as their
ammunition. The insectaries are about 100-feet by 30-feet rectangular
pieces of land that are enclosed by metal flashing that is inserted
four inches into the ground, and protrude eight inches high. Knapweed
is planted within the metal flashing and purchased insects are then
placed inside the insectaries. Williams estimated the female insects
may lay 100 larvas annually and the surviving insects multiply by as
much as 90-times their original amount.

After the insects have matured, the students capture and release them
along appropriate roadways and fields. Students then monitor progress
through the use of a GPS-system, which locates the sights and
photographs the area. The GPS-system also allows the students to
monitor the progress of the insects and reduction of knapweed plants by
counting the insect to knapweed plant ratio.

Root boring weevils kill knapweed by burrowing into the plant’s root
system and eating the root. The seed head moths land on the plant’s
blossoms and lay larva on the plant’s seeds. The larva, when hatched,
feed on the florets and seeds of the spotted knapweed. This inhibits
the seeds from dispersing creating more of the noxious weed.

The two insect species being used were the same ones that kept the
noxious weed under control in Asia, which is where spotted knapweed is
believed to have come from. By reintroducing the two, MDT hopes to help
balance the plant ecosystem.

The biological approach is a "slowly but surely" method because as the
insects travel, they kill knapweed and inhibit future growth. Chemical
herbicides, although immediately effective, kill only the sprayed weeds
and the chemicals used do not spread beyond that specific area.

According to Williams, MDT can spray and kill knapweed along highways,
but if the adjacent landowner is not able to maintain the knapweed, it
will simply re-develop.

Knapweed was introduced to Montana in the early 1900’s and now
contaminates all 56 Montana counties, it is considered Montana’s number
one problem weed.
Knapweed spreads rapidly by seeds hitching rides on vehicles, humans,
animals, and through wind and water. Seeds can remain viable in the
soil for seven to ten years.

MDT uses a number of methods to manage every problem weed and is
excited about the interest each school is showing for the fight against
knapweed.

"It is a great way to educate youth and employ another method of
control, instead of depending solely on herbicides," Williams said.

Although this biological weed control method is not immediately
effective, Williams does believe it will be incredibly sufficient in
the long run.

"This is a Johnny Appleseed story," William said. "We are planting
shade trees for our grandchildren."

Dan Williams, MDT maintenance division (406) 444-7604
Charity Watt Levis, public information (406) 444-7205

For more information, please contact Dan Williams at (406) 444-7604.
For the hearing impaired, the TTY number is (406) 444-7696 or
1-800-335-7592 or Montana Relay at 711.