Colorado potato beetle

Propaganda usually uses things that are to silly to be true ;) Still, it is quite effective to turn people against one another. But it really is amazing that one hungry bug can be used as a weapon to discourage people from American imperialism.

Yeah, indeed, it was brought to Europe on the turn of the 19th century, supposedly by accident on ships with food. What is even more interesting, it was used in anti-imperialist propaganda newspapers as a main reason for food deficiencies. They claimed that the pest was dropped on purpose by American planes into the Baltic Sea, from where it got to Poland to destroy our crops (mostly in the 1950s).

Yeah they can be quite nasty... They have developed resistance to all major insecticide classes, although not every population is resistant to every chemical.