If one drone isn't enough, try a drone swarm

When Bill Herz wants to know how his crops are doing, he launches a drone.

He has nearly a thousand acres of corn and soybeans in LaSalle, eastern Illinois. "My drone has saved me time and energy," he says.

"I don't need to walk a whole field to find a problem area. I can fly the field, look at the results and go right to it."

Drones used for farming belong to the arsenal of tools used for precision agriculture - hi-tech farming using data to make better decisions.

So far, flying robots have enabled farmers to live stream crop growth, patrol for pathogens and boost farm efficiency. The next step is to recruit squadrons of them that can co-operate and carry out their tasks without the need for a human pilot.

Scientists from the Norwegian Defence Research Establishment (FFI) and the US's Rajant Corporation are working on simultaneously flying about 20 drones that can work in co-ordination with little human supervision.