[tremon]

Still, it appears to be very good at disrupting the enemy's economy.

Not that I think it was engineered as a bioweapon, but it does show that bioweapons don't have to be deadly to be effective.

[aerostable_slug]

One of the best bioweapons is Tularemia, and part of that reason is its general lack of lethality. It temporarily renders the exposed population incapable of putting up a good fight, but it kills relatively few. Escape isn't that big a deal (because again, it's not very lethal), and it's easy enough to inoculate one's own troops against the particular flavor being used.