It's called 'entomological warfare'--the use of insects in war. The Japanese used crop-destroying insects in China, during WWII. The Americans may have experimented with this during the 'Secret War' against Cuba, in the early 1960s. Paleolithic tribes used beehives to flush enemies out of caves. It wouldn't surprise me if the US government experimented with ticks.

As someone with Lyme disease, I've always thought this was one of the more ridiculous conspiracy theories. Ticks and bacteria that weaken the host make great co-evolvers. It's a very beneficial relationship for them.