The USDA, in partnership with states in the west, has introduced numerous
beneficial insects that eat knapweed in pastures. They place the insects in
field cages -- like hotcaps made of netting that lets in air and light --
over knapweed plants.
Eventually the insects multiply, and are let out of the cages to spread.
It's not quick like herbicides. Depending on how many insects you initially
release to eat the knapweed, etc., it can take a few years before the
knapweed disappears. I know there are some companies [I believe in Montana]
that collect the wild weed-eating insects and sell them, but it is a bit
late at night out my way to look up the companies in my files.
Your friend will need patience if he wants a biological solution instead of
the quick miracles of herbicides and their side effects. On a small area it
is alot more feasible and quicker than what the USDA and states (Canada,
too) have been trying to do with weed biocontrol over vast expanses of
federal grazing land. But the initial investment in collecting and testing
and quarantining these European weed-eaters has already been done, and it
would not take much for your friend to reap some of the benefits of his
federal tax dollars that funded the importation of these weed-eating bugs.
independent writer and former agricultural pest control adviser
<I've been asked by a friend to help find alternatives for the control
<of a reasonable small area of knapweed (not acres of it). The local
<advice has all been to use 2,4,D or Roundup in a small pasture that
<is grazed by llamas. They were told that if the animals aren't
<pregnant, they wouldn't have to be pulled off the pasture during or
<after spraying. They are concerned about that, but also recognize
<it's a fast spreading and difficult to contain weed in their area.
<Any advice for them?
<Thanks a lot!