I think you may be putting the cart before the horse here.....
Despite what you may have been told, the contrails you see are almst certainly made by commercial jets which are easily identified by any of the flight tracking websites on the web. here is just one example:
http://flightaware.com/live/
Here is a guide to the hobby of planespotting with some informative links to help identify the planes by type and decipher tail numbers:
http://www.bruceleibowitz.net/spotting.htm
Since aircraft and traffic control also transmit information by radio, some planespotters also use scanners to help in ID'ing the planes they see.
But don't stop there. Should you then conclude that the commercial jets are spraying, document the exact identity of the planes using telescopic photography like these hobbyists are doing:
http://www.luchtzak.be/forums/viewforum.php?f=25
Here is an example of how to do it:
http://www.skystef.be/contrail.htm
Here is an example of the equipment:
http://www.skystef.be/scope-setup.htm
As you can see here, sufficient resolution is available to see the aircraft identification numbers:
http://www.skystef.be/contrail4.htm
This page shows US Air Force jets up to 38,000 ft in which the tail numbers are visible:
http://www.skystef.be/contrail/united-states-air-force.htm
Lastly, ask yourself why, in the 14 year history of this hoax, the main promoters such as Michael J. Murphy have not told their followers about this method of solving the "conundrum" they have started..........
Jay Reynolds