Workshop on New Grass Germplasms
37
Monument Creek. Agents released for leafy spurge are Aphthona lacertosa,
A. nigriscutis, and A. czwalinae. At the Monument Fire Center site, noxious
weeds include Canada thistle, diffuse knapweed, leafy spurge, musk thistle,
and Dalmatian toadflax. Releases there include Brachypterolus pulicarius.
Releases at the Department of Energy's Rocky Flats Environmental Tech-
nology Site began in the spring of 2001. The program is integrated into an on-
going weed integrated pest management (IPM) program. Noxious weeds at this
site include Canada thistle, diffuse knapweed, musk thistle, field bindweed, and
Dalmatian toadflax. At this site, Mecinus janthinus was released to control Dal-
matian toadflax.
Successes
Knapweed control at Fort Carson has been highly successful. Four of six
insects have been recovered. L. minutus is present in sufficient densities to begin
redistribution. C. achaetes is prevalent and significant damage is evident. U.
affinis is present, but there may be competition with U. quad. C. acrolophi has
also been recovered, but its impact is unknown.
R. conicus was previously established at Fort Carson on musk thistle, and
is easily recovered. T. horridus was released in 1999 and has had a synergistic
effect. This combination is reducing musk thistle density at three sites at Fort
Carson.
Although the program at the Air Force Academy is not as advanced as at
Fort Carson, it is proceeding rapidly. Knapweed and spurge insects are well
established. We have recovered Cassida rubiginosa and Larinus planus on
Canada thistle--a first for this area. Mapping weed and insect densities con-
tinues, and new releases will be made in 2002.
Disappointments
Canada thistle has been the most difficult target to address. Although C.
rubiginosa and L. planus have been recovered, impact is slight at present. Com-
petition from ants tending aphids and leafhoppers may be one of the reasons why
the biocontrol agents are not effective. We noticed this effect when sites at Fort
Carson, which had a lot of ants, differed from sites at the Academy, which had
few ants, in C. rubiginosa and L. planus establishment.
A problem with Canada thistle is that insects such as L. planus and C.
rubiginosa are targeted at the seed head and upper leaves, and they do little to
limit spread because of the thistle's extensive root systems. Commonwealth
Agricultural Biology International (CABI) is conducting surveys in Russia and
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