Hi Bill and All:

>For example, in the article the half life of imidacloprid is discusses
>and it varies from reasonable to over a year.

Your EPA in the US uses the figure of one year.  They are the people who
register it I believe, and I expect as in Canada that is an average of
experimental values.

The half life of a
>pesticide does vary depending on the application method and
>when/where/how and the conditions under which it is applied.

We are talking about application to the soil by either injection, in furrow
treatment or seed treatment.  The foliar application has a much shorter half
life.

So you
>could bias your findings to have either a long or short half-life. And
>where is the pesticide after it has done its thing?

The vast majority of the insecticide is staying within the top 30 cm. of
soil (I have references for this, but not at my fingertips).  The people
measuring half life are measuring the amount in that depth of soil.  They
rarely sample deeper than that.

Is it in a place
>where it is still in the system to continue to cycle through its killing
>or is it there but benign, even at half strength because it is tied up
>in plant material/soil/whatever?

It is often bound to organic matter.  If you look at the half life data you
will see that it is often given in relation to soil type.  When the chemical
is bound to organic matter it can break down faster (because of the larger
amount of bacteria in that location).  However, organic matter is where the
roots in soil feed, so it available to plants from that location.

>A pesticide applied in Florida will be out of the system much quicker
>than one applied in Canada, especially if both were applied in the fall.
>But if you wanted to show it was a good pesticide, take the Florida
>data. If bad, take the Canadian.

I would say if you live in Florida and data is available, take the Florida
data.  But if you live in the Northern US or a potato growing region of
North America similar to PEI (like *Maine*, Bill), we have a study here
which I have already quoted showing that the half life was 366 to 457 days
with a soil concentration ranging between 30 and 35 ppb after 24 months.

>We have conflicting data on imidacloprid. You have the anecdotal
>evidence that it is bad from the French Beekeepers and reports from PEI.

You also have a country (France) which spent several million dollars
studying the pesticide and honeybees and after that study has continued to
ban it.

>You have "science" from the pesticide haters saying it is bad and
>"science" from Bayer and others, including studies on canola in Canada,
>saying it is fine.

You have one study in Canada, paid for by Bayer, looking only at obvious
lethality (mainly dead bees in front of the hives) which is still
unpublished and therefore cannot really be criticized.  If the study is so
clear why the delay in publishing it?  It has been requested several weeks
ago by the PMRA of Canada.

> But the greenhouse growers have OK'ed it if applied
>properly. One would hope an organization with that much self interest
>would be circumspect in the use of pesticides, and apparently
>imidacloprid is fine after a month's wait.

Well why then does the largest supplier of bumblebees to the greenhouse
industry, Koppert, specifically caution that the bees should NOT be
introduced for a minimum of 45 days after application.  And remember, Bill,
those bumblebees are basicly a disposable pollination unit.  Even if the
colony is harmed by the toxin, as long as it is still able to pollinate the
crop before it collapses it as an acceptable situation.

Moreover, Bill, what is the application rate in the greenhouse?  Check with
a potato grower near you and you will likely find that they are applying
from 250 to 350 grams of active ingredient per hectare (the application rate
on sunflowers for comparison is 50 grams per hectare).  The highest rate the
company has ever considered registering is 450 grams per hectare, and I do
not know if they succeeded in registering that, I am just taking that figure
from a soil persistence study by Bayer in which they made that statement.
That study (by Vogeler, of Bayer) showed residue levels of 2,500 ppb in
wheat straw in the second crop of wheat (270 days after application, I
believe) and about 1000 ppb in wheat straw in the third crop of wheat after
the initial application. (about 410 days after application).  The levels of
toxin in the first and second crops were nearly equal.  So it was not
fitting in to what you call "reasonable", Bill.  And that was at application
of 450 grams a.i. per hectare, just a little more than they are likely
putting on potatoes in a field near you.  The main difference I see in PEI
is that about one out of every five acres here is in potatoes, so we are
just seeing the effects a little sooner.

Just my anecdotal humble opinion, of course :)

Regards
Stan