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I have been waiting a long time to answer to this thread as I collect
my thoughts... There is more to this evolving knapweed "story"...<br>
------------------------<br>
Biocontrol Insect Exacerbates Invasive Weed:<br>
This may be the case in some sights however, what we are seeing in
many spots in SW Montana is that the knapweed seed head weevil <i>Larinus
minutus</i> soon comes in and starts to infect a large percentage of
the seed heads, displacing the gall flies. These weevils are not
present in the seed heads during winter (they overwinter as adults) so
this decreases the mouse food source. This is followed by<i> Agapeta
zoegana</i>, the root boring moth which does not seem to usually kill
the plant but may shorten its life span [both <i>Larinus</i> and <i>Agapeta</i>
disperse well by flight]. Then if we follow up with the knapweed root
boring weevils <a
href="http://mtwow.org/Cyphocleonus-achates-description.htm"><i>Cyphocleonus
achates</i></a> (a very exciting bio-agent!), we finally are seeing
spotted knapweed slowly decrease in density and in some sites in the
Whitehall area and in other MT spots, almost completely disappear. <a
href="http://mtwow.org/Biological_Control_Before_&_After.html">http://mtwow.org/Biological_Control_Before_&_After.html</a><br>
Cypho. is a large flightless weevil that only attacks plants with a
larger tap root (2-3+ yr. old plants). Therefore, the effect we are
seeing is that they knock out most of the larger/older plants in a few
years and then it takes 8-12 years to use up most of the soil seed
bank. <a
href="http://mtwow.org/Blue-Bird-Mine-Release-Site-sick-plants.html">http://mtwow.org/Blue-Bird-Mine-Release-Site-sick-plants.html</a><br>
The seed head feeders take out most of the seeds, <i>Agapeta</i>
weakens things and Cypho finish off the larger plants. The sites will
often go from many large knapweed plants to even more smaller plants
[per square meter] as the seeds in the soil sprout after the large
plants die, to a slowly decreasing density of knapweed as the native
plants slowly come back as knapweed decreases.... <a
href="http://mtwow.org/Blue-Bird-Mine-release-site-views.html">http://mtwow.org/Blue-Bird-Mine-release-site-views.html</a><br>
In MT places like the Bitterroot Valley So. of Missoula where
knapweed has dominated for a very long time there is almost no native
seed left so, cheat grass unfortunately often replaces the knapweed.
Further E. in our area (between Butte and Bozeman) where the knapweed
stands are younger and not as dense, we are seeing the natives able to
come back in, as this 8-12 yr. process proceeds.<br>
This complex of insects seems to be what is needed and Cypho. are
the crucial insect after the seed head feeders build up.<br>
We are mass rearing Cypho in insectaries at a number of MT and ID
high schools. The Ag. Experiment Station in Corvallis, MT started the
insectary rearing of Cypho. Because Cypho. do not fly we are busy
being "Johnny weevil seed" all over the State. <a
href="http://mtwow.org/insectary_ag_experiment_station_corvallis_mt_05.html">http://mtwow.org/insectary_ag_experiment_station_corvallis_mt_05.html</a>
<br>
Cypho. pops. are building up nicely at many sites in MT.<br>
Whitehall insectary: <a href="http://mtwow.org/knapweed-insectary.htm">http://mtwow.org/knapweed-insectary.htm</a><br>
<br>
To conclude: Biocontrol Insect Exacerbates Invasive Weed is a real
effect however, I feel that it is short lived as the other bio-agents
within the imported complex become established, this problem will go
away, as will much of the spotted knapweed.<br>
<br>
-most of the above statements are anecdotal...<br>
-my personal goal is a release of Cypho. every 1/4 section where ever
knapweed occurs.<br>
<br>
Todd Breitenfeldt<br>
Whitehall High School sci. teacher<br>
Whitehall Biological Weed Control Project Coord.<br>
<a href="http://mtwow.org/">http://mtwow.org/</a><br>
---------------------------------------------------------------------------------------------<br>
<br>
Olivia Kwong wrote:
<blockquote
cite="midPine.LNX.4.64.0809290927010.29703@cpanel1-bb.epconline.net"
type="cite"><a class="moz-txt-link-freetext" href="http://www.sciencedaily.com/releases/2008/09/080903134405.htm">http://www.sciencedaily.com/releases/2008/09/080903134405.htm</a>
<br>
<br>
Biocontrol Insect Exacerbates Invasive Weed
<br>
<br>
ScienceDaily (Sep. 5, 2008) -- Biocontrol agents, such as insects, are
often released outside of their native ranges to control invasive
plants.
<br>
<br>
But scientists in Montana have found that through complex community
interactions among deer mice, native plants and seeds, the presence of
an introduced fly may exacerbate the effects of the invasive plant it
was meant to control. The authors report their results in the September
issue of the journal Ecological Applications.
<br>
<br>
See the link above for the full article text.
<br>
<br>
<br>
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</blockquote>
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