Friday, October 10, 2008

Splitting Pesticide Hairs For The Informed Customer

If you're like me, thinking too much about chemistry makes your head hurt. I mean who gives a flying fig what Mole equals (1 mole of atoms or molecules contains 6.022 x 1023 atoms or molecules). We don't want to think about it. We just want it to work!

Unfortunately, in our advanced society, a lot of things work. Chemicals are lined up to kill what we want them to kill. They are eager to do our bidding. So, how do we decide between them?

Well, like a gal deciding between suitors, we must get a little more clever with our criteria. It's no longer good enough that a chemical does what we ask of it. We need to see what it's doing behind our backs. How does this joker deal with the birds and the bees? How will this prize fighter affect my friends like water and soil? Finally, does this dude know when to take a hike? I mean we had one date. That does not a life-long commitment make!

For those of you not lost in my exaggerated imagery, what I'm trying to say is that chemicals have a lot of characteristics that we must investigate. For the purpose of this discussion I'm taking two commonly sold active ingredients. Imidacloprid is one that we see in Bayer's Tree and Shrub drench, Bug Blaster lawn insecticide granules, and many others. The other is Acephate which we see in Orthene, Lancer, Pinpoint, etc.

As of late, I have measured pesticides by their effects on beneficial insects. "Protect the bees," I've said again and again. Imidacloprid is bad for them, and so is Acephate, if sprayed on plants where they forage. (This is why we recommend horticultural oils and soaps so often.)There is so much more to discover though.

For help with the technical stuff I consulted The National Pesticide Information Center. My concern was Imidacloprid's effect on bees if used as a systemic drench. I wondered if the toxic chemical would reach the flowers and affect bees through the pollen. The answer is no. It will not.

"What about Acephate?" I asked. This is where our comparison moved beyond bees to the overall effect of the two choices on the environment. Pesticides are better if they do their job and then get the heck out Dodge. We don't want them lingering in soil and water. Scientists measure the break down of chemicals in half-lives. A half-life is the time required for half of the compound to degrade or go away.

Acephate has a half-life of four days.
If you apply it to sandy soil like ours, it will be 97% degraded in five half-lives which equals twenty days. For twenty days, it is hanging around in the dirt. According to the NPIC, however, it has a low chance of moving into the water table.

Imidocloprid has a half-life greater than one year.
If you apply it to sandy soil like ours, it will be 97% degraded in five half-lives which equals five years. For five years, it will be in our soil. According to the NPIC fact sheet, this pesticide is more mobile in the ground, and may have affects on ground water.

So, there is reason to expand our knowlege of these products beyond dilution rates. There is more to learn, and people willing to teach us. It's not hard. It's chemistry, not rocket science.

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