Communist Crop Pests, 1960.

The advertisement is selling crop spraying equipment, and it's quite a small ad, so there's no time for them to explain the references. First, a critter, wearing a military cap adorned with a star, is holding up a sign that reads, "The 5th Column to Hold Up American Farmers." The ad's copy reads, "Farewell, Comrades! Our training to destroy American farm crops not up-to-date on Comfort Multi-Purpose Sprayer.". A "Fifth Column" is an organized group of moles or dissenters, thwarting war efforts from within a country. However, the style of dress of the head 'critter', and the broken english used for his speech would indicate that the critter is intended to be an invader from the Soviet Union. So, who are these invading armies? My best guess is the Russian aphid, a common wheat and barley pest in the midwest. Today, selling insecticide by Photoshopping a suicide-bomber vest and turban onto an anthropomorphic insect wouldn't go over so well; times were much different back when enemies were clear and well-defined.