Hi Jerry and all:

> Although the verdict may still be argued, many of the newer chemicals 
> appear to  be
> less toxic, less persistent than the older chemicals.  So, if you 
> advocate
> banning these, keep in mind what the alternatives might be.

That's an interesting idea, Jerry.  Lets look at toxicity first.  Since we 
are a bee list, lets look at toxicity to bees:

From my Hive and Honeybee here are some LD50  (Lethal dose for 50% of the 
bees tested) values for honey bees of some of the most toxic insecticides in 
use when the table came out in 1973 (DDT had already been withdrawn from 
most uses in the USA by then):   By the way, they are 24 hour LD50 values.

tepp  0.001 micrograms / bee   (1 nanogram)
chloropyrifos   0.114 micrograms / bee (114 nanograms)
all these below are micrograms / bee:
dieldrin  0.139  carbofuran 0.160  parathion  0.175  dimethoate 0.188
and so on, but the LD 50 dose keeps going up.
There are 29 listed with LD 50 below 1 microgram (1000 nanograms).  There 
are a further 11 with LD 50 more than one microgram:
Imidan  1.06  carbaryl (Sevin)   1.34
That is the "highly toxic" group of insecticides.  There is a further 20 in 
the "moderately toxic" group with LD 50 greater than 2 micrograms / bee.

Now let us look at Richard Schmuck (of Bayer) in Pest Management Science, 
who gives the LD 50 for imidacloprid as being between 3.7 and 40 nanogram / 
bee.  That is 0.0037 to 0.040 micrograms.

If we use either figure, there was only one of forty insecticides in the 
"highly toxic" group (only one of 60 in the total group of insecticides used 
in 1973) that was more toxic than imidacloprid (that was tepp).

If we were looking at toxicity to birds or mammals, the results would be 
very different.  But we are a bee list after all.

Now let's look at persistence:

The Hive and Honeybee footnotes for this LD50 list states that the most 
toxic, tepp, and also dibrom and phosdrin "have such short residual activity 
that they kill only bees contacted at treatment time or shortly thereafter. 
These materials are usually safe to use when bees are not in flight".

By contrast, imidacloprid is designed to have a very long half life, so it 
can provide season long control in the plant.  In PEI, the half life in our 
acidic soils, with a low organic matter is over a year.   A forester in 
Virginia making representation to your Department of the Environment for the 
continued registration of imidacloprid stated that they were getting 7 years 
control of a pest with soil injection of imidacloprid.  I have previously 
posted articles from forestry journals stating that they got two or three 
years control.

So, I don't think that I would worry too much about the older insecticides 
being worse than imidacloprid as far as persistence goes (with the exception 
of something like DDT, which turned out to be quite stable and which was why 
it was already withdrawn by the time this table came out).

But, the new insecticides have big advantages for farmers.  They don't have 
to spray, because the plants are turned toxic themselves.  That is a savings 
of fuel, labour, equipment.  And it also means less complaints from 
neighbours which is a big consideration.

Peter Borst wrote:

>I would just like to add one small note. Much is made of the role that 
>beekeepers play in helping to produce our food supply. However, most of the 
>work of getting food raised and on the table is done by other people, who 
>also have the right to make a living.

I am a farmer, Peter (I just spent the weekend spreading 30 big loads of 
manure).  Many of the people on this list are farmers.  Jerry, you I believe 
are a farmboy, to judge from your posts.   I am not attacking farmers.  Nor 
am I pushing any "organic" agenda,  although my own views tend towards this. 
But on the basis of the figures I just posted,  I just have a difficult time 
understanding why you think that the older insecticides were so much worse 
than imidacloprid.

Stan

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