I still haven't found anything official to verify the use of creosote. At the time, I wasn't too concerned about the actual substance. Every year, farmers and the USDA set marketing orders to determine standards for the year's crop - including size, quality, and quantity of the produce. Whatever doesn't fit the marketing order has to be disposed of in a way that doesn't create a black market that will undercut the crop standards and prices set by the marketing order. Sometimes, that has involved pouring vile substances on the produce to make it inedible. So, when Woody said creosote, I didn't question it. It's readily available on farms, and would certainly do the trick.
-Joe-