> However, what I want to know is, is there any valid reason not to spray
>loosestrife infestations judiciously with Roundup? It kills the whole
>plant, biodegrades rapidly and is nontoxic to mammals and birds. Pulling
>on the other hand doesn't remove entire root systems and the plants keep
>coming back. (Not to mention the labor intensive nature of pulling.)
>Nonetheless, I'm all in favor of biological controls if they really work.

I'd expect that since loosestrife is a wetland plant, you'd need to use
"Rodeo", the wetland version of Roundup, which is less toxic to aquatic
organisms. I don't have my Roundup label handy, but as I recall, there is
a minimum allowed distance to open water to be able to use it legally.
Also, I've seen some mention by botanists that Roundup residues may be more
harmful to native plants than to our tame, less fussy ones. Also keep in
mind that most commercial formulations of pesticides tend to have some
nasties hidden under the 'inactive' (sic) ingredients. In Roundup's case,
the surfactant they use is about 20 times more toxic to mammals than the
active ingredient glyphosate, but they are allowed to hide that from the
consumer, and push the lower glyphosate toxicity instead :-( For
large-scale use, and with whatever permits may apply, you may be able to
buy the pure glyphosate.

In any case, you should contact the King County Weed Control Board
(206-296-0290) and ask them what they are currently recommending; they'll
be able to tell you about what works and what doesn't, and which permits
you may need, especially near a wetland. You may need permits to do any
control of purple loosestrife, the stuff is so nasty. It is officially
under quarantine throughout King County (including Seattle), so it is
illegal to transport any plant part, or cause it to spread in any way.
It's conceivable that killing it with herbicide at the wrong time of year
could cause seeds to be released such that they'd spread farther than if
you left them alone. (For perennial weeds, glyphosate should be usually be
applied after seed heads appear, which is when they start sending stuff
down to the roots for storage.) According to a brief pamphlet I have from
the weed board: "The surest control technique is hand removal by digging
the roots and subsequent replanting with native vegetation to discourage
regrowth. All parts of the stem and and roots should be securely bagged
and burned or transported to landfill to prevent further spread.
Particular care must be taken once the plant is in bloom. Clip seedheads
off and seal them in a plastic bag before digging the plant. Hand cutting
the plants at ground level several years in a row can also be successful if
the plants are cut frequently enough to prevent renewal of the root masses'
store of nutrients."

I have the 1996 WA state weed list online, along with some useful phone
numbers for more information at:

http://chemwww.chem.washington.edu/natives/noxious.html



Allyn Weaks allyn at u.washington.edu
allyn at cornetto.chem.washington.edu
Pacific Northwest Native Plant Gardening:
http://chemwww.chem.washington.edu/natives/