Scientist and the military are very interested in controlling insects in general. Essentially their brains are nothing more than a stem, and they are purely instinctual. Through the use of chemicals and electronic stimulus they are attempting to turn them into controllable robots. Who knows what their applications may be? The more they learn about the effects of chemicals on the bug-brain the closer they get to making perfect little spies.
I can see the military using the chemical to start a locust swarm into the enemies ground troops. I think they will eat most anything they come in contact with if it is edible. This will allow the advancing military to take control of the areas left ravaged by the locusts. As they follow closely behind the locusts they can kill the opposing army easily as they will be confused.