Plant systems, the “base” of our food production system, have been targeted by military and other groups several times throughout history.
In the year 346 BC, while battling Carthage, the Romans spread large quantities of salt on cultivated fields creating toxic conditions for crops. This forced local citizens to abandon the area, ultimately influencing the outcome of the war.
During the U.S. Civil War, the Confederacy alleged that troops from the Union deliberately destroyed crops in the southern region of the U.S. by intentionally introducing an insect known as the harlequin bug, Murgentia histrionica. The insect caused great damage, but the direct connection to the Union was never proven. The appearance of this insect species may have occurred naturally since it was indigenous to Mexico.
In World War II, Germany was accused of dropping containers of Colorado Potato Beetles on Britain. The reports indicated that these “bombs” were made of cardboard and each contained as many as 100 beetles. However, this allegation has been widely debated, with some suggesting the insect's appearance in England actually occurred as a result of an accidental introduction through food shipments. However, Germany did have a “potato beetle research” program, set up as a defense program to counter Allied biological weapons research. Also during the second World War, the Soviet Union was alleged to have developed and used different types of fungal disease agents on wheat and other cereal crops in enemy countries.
During the Cold War between the U.S. and U.S.S.R., both countries stockpiled tons of wheat stem rust spores, a serious disease that can wipe out a wheat crop.
Plant-based food products intended for direct consumption by people have also been targeted by terrorist activities in the past. In 1989, the U.S. Embassy in Chile received a call declaring that grapes moving from Chile to the United States and Japan were contaminated with cyanide.
In fact, after investigation by the FDA, two contaminated grapes were found. However, because the amount of cyanide found was so small, the contamination wasn't deemed to be a real threat to human health. As a result of the event, several countries cut off importation of several fruit products from Chile. Chilean growers claimed losses of more than $300 million.