PHI 21 for apples & corn means that the waiting period to harvest is 21 days after the product was applied.

PHI of 1 for lettuce means must wait 1 day.

To learn why those numbers are so different, call the 1-800 number on the label.

If it were only that easy...

I know what the company is telling me to do. Spray lettuce & eat it the next day, Spray sweet corn & now wait 21 days to eat it.
It just doesn't make sense.
As far as the 800#, the gal there reads me a prepared statement saying roughly, "the PHI recommendations are based on limiting ingestion to safe amounts based on growth patterns"
When I zeroed in on how the numbers don't make sense to me, I could imagine her deer in the headlights expression through the phone line.
So I was hoping someone here had a little more scientific explanation...

Apple and corn have more storage products which slower metabolism is my WAG.

Dan

I have no idea either. Triazide is a tradename used by Spectracide for Lambda-Cyhalothrin. This chemical is a pyrethoid which could be considered a synthetic form of Pyrethrin. http://npic.orst.edu/factsheets/l_cyhalogen.pdf http://www.ipm.iastate.edu/ipm/iiin/node/95 It is widely marketed for lawn use. I have not seen a vegetable version. However it is a low toxity product aimed at homeowners rather than commercial applicators. It has relatively long half life (slow to break down)so I would have difficulty accepting a 1 day harvest interval for broccoli or lettuce. http://www.pesticides.gov.uk/PSD_PDFs/Evaluations/104_lambda_cyhalothrin.pdf
The PHi may have more to do with residue tolerances than actual toxity http://www.fluoridealert.org/pesticides/lambda-cyhal.fr.mar.27.1995.htm

"Triazide is a tradename used by Spectracide for Lambda-Cyhalothrin"

That is version #1 which was not listed for fruit trees.(but was for vegetables)

Version #2 Gamma-Cyhalothrin has fruit trees as well as vegetables.

One can always eschew consuming and using the product if one doesn't trust the chemical formula.

Dan

The issue of even using it aside - Speculation:

(1) various amounts of liquids and starches in the produce, with lettuce having the highest water content and the least amount of starches, and the effect that dilution and lack of starch binding has on the toxic levels.

(2) the amount of the food product likely to be consumed in one sitting ie: 3-4 lettuce leaves vs. 1-2 ears of corn or an apple.

As mentioned, logically if concerned then don't use it.

Dave

I agree with the OP, it doesn't seem logical.

But, there are probably (possibly?) valid scientifically based reasons for those days -- we can hope.

Some of it is more about the politics/procedures of pesticide approval process, too, I think.

That being said, I really, really like the Triazicide product(s), have had good results, and I personally am of the opinion that pesticides, if used with normal care, are NOT our biggest dangers in this world. But, hey, I have to drive the freeways of Detroit every day to get to and from work, talk about life threatening!

Thanks Dave digdirt for speculation 1 & 2.
A little bit of "why" has always been better than "just say no" at my house.
In summer, when my lettuce is "free", I usually eat a head, not 3-4 leaves.(yum!)
Anyway, I try to time my applications so that at least a week passes before I pick & eat anything.
And denninmi,
If you have a job in Detroit, you are indeed a lucky one!

That may be the explanation. Lambda-Cyhalothrin and Gamma-cyhalothrin are two different chemicals. Well actually Gamma is a resolved isomer of Lambda but it has differnt properties. Most Spectrum products are Lambda, but One and Done is Gamma

I usually eat a head, not 3-4 leaves.

Valsound - maybe I should have said "normally" consumed. :)

Dave