h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Operation Vegetarian was a British military plan in 1942 to disseminate linseed cakes infected with anthrax onto the fields of Germany.
These cakes would have been eaten by the cattle, which would then be consumed by the civilian population, causing the deaths of millions of German citizens.
Furthermore, it would have wiped out the majority of Germany's cattle, creating a massive food shortage for the rest of the population that remained uninfected.

The cakes themselves were tested on Gruinard Island, just off of Scotland.
Because of the widespread infection from the anthrax, the land remained contaminated until 1990.
However, the five million cakes made to be disseminated in Germany were eventually incinerated when WWII was ended on 1945, making the plan useless...



and here is a follow up http://en.wikipedia.org/wiki/Gruinard_Island