A number of bacteria, viruses and toxins pose a significant threat to human beings, but plenty of the world's biological agents prefer different prey: cultivated food crops. Cutting off an enemy's food supply is a time-tested military strategy, whether you're defending your homeland against an invading force or besieging a walled city. Without food, populations weaken, panic, riot and eventually die.
Several countries, especially the United States and Russia, have devoted a great deal of research to diseases and even insects that target key food crops. The fact that modern agriculture typically focuses on the large-scale production of a single crop only sweetens the deal for the architects of blight and famine.
One such bioweapon is rice blast, a crop disease caused by the fungus Pyricularia oryzae (also known as Magnaporthe grisea). The leaves of affected plants soon develop grayish lesions composed of thousands of fungal spores. These spores quickly multiply and spread from plant to plant, sapping the plants and leading to much lower crop production. While breeding resistant plants is a good defensive measure against some crop disease, rice blast presents a problem because you wouldn't have to breed resistance to one strain of fungus, but 219 different strains.
Such a bioweapon wouldn't be as sure of a killer as the likes of smallpox and botulism. It could however lead to severe starvation in poorer countries, as well as financial losses and other huge problems.
A number of countries have pursued rice blast as a biological weapon, including the United States. By the time the U.S. dismantled its anti-crop program, it had amassed nearly a ton of the harmful fungus for a potential attack on Asia [source: BBC].
What's that? You prefer a nice hamburger to a rice dish? Well, our next entry proves that you meat eaters aren't safe either.