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Re: synthetic pyrethroids

I don't think that Jerry means to imply that the natural pyrethrins
*aren't* toxic to insects, bees, spiders and other creatures, I'm sure he's
pointing out that the synthetic pyrethrins only exacerbate the problem.

"They [the synthetic pyrethrins] are also slightly different in efficacy.
They persist a bit longer,
sometimes for a few days.  They are more toxic to insects.  And they share
some of the downsides to most broad spectrum insecticides:  they
indiscriminately kill predaceous("good") insects and phytophagous("bad")
ones.  SP's reliably kill honey bees, for instance.  They also *can* kill
birds but it would take a concerted effort to actually do so."

It's true that natural pyrethrins only last a few hours and synthetics last
longer. But, I find it is  difficult to find a product today that only
contains natural pryrethins, almost all are "laced" with the synthethic
form to boost killing time.

What bothers me most is that whether natural or synthethic, too many folks
are swayed the marketing terms on labels such as "organic", "safe--made
from flowers", "nature's insecticide", and so on. They are lulled into a
false sense of security to use the product at will.

Whether natural *or* synthetic pyrethrin, these presticides kill many
beneficial insescts. The difference is one of length: a honey bee may be
spared if it comes by a plant sprayed xx number of hours before with
natural pyrethrin, but if the spraying was done with a synthethic product,
the bee may be spared only if it delays its visit by xx number of
additional hours.

I rarely use pyrethrins of any type, mentally classifying them along with
all their other pesticide "cousins".  (I find that many insects killed by
pyrethrins are also killed by insecticidal soap). If you do find it
necessary to make use of pyrethrins, I suggest looking for one that does
not contain a combination of natural and synthetic pyrethrins. Second,
spray at the end of the afternoon when bees have stopped feeding (hopefully
the pesticide has lost its toxicity by times the bees arrive the next
morning). Third, only spray the infected plant, not any wholesale spraying
of the area.

Carol Moholt



                         The Bay Area Gardener <http://www.gardens.com>
                 **serving gardeners in the greater San Francisco Bay Area**
                       * email: moholt@gardens.com * phone: 650-968-4480 *
                           301 Windmill Park Lane, Mtn. View CA 94043
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