Papago Farms, Ariz. ? A rusty barbed wire fence is all that separates the United States from Mexico in this stark, dusty area of the southern Arizona desert.

It’s been mangled in places, cut in others, providing little deterrent to the thousands of illegal immigrants who slip through the border daily in countless places like this.

Stemming the influx along 350 miles of border in Arizona has been a daunting task for the Border Patrol. As the busiest illegal crossing point on the U.S.-Mexico divide, this stretch of frontier was a natural for the nation’s first homeland security use of unmanned aerial vehicles.

Two Israeli-made Hermes drones leased by the Border Patrol are due to take to the air this summer to help agents spot, track, seize — and sometimes rescue — illegal crossers.

Concentrated mostly along a 220-mile western stretch of border that includes an Indian reservation, a wildlife refuge and a military range, the drones are only the latest hardware in the patrol’s technological toolbox — which includes tower-mounted cameras, ground sensors, night-vision goggles and portable lifts that let agents view down lines of highway traffic.

The hope is the drones can help stem a surge in illegal immigration that a buildup of border agents hasn’t stopped.

The remotely piloted Hermes 450 craft, which can stay aloft for 20 hours at a time, are not armed with missiles like the Predators that gained renown in U.S. military and CIA operations. Predator-fired missiles have killed several top al-Qaida operatives in Afghanistan and Yemen.

The Border Patrol drones will carry cameras with thermal and night vision capabilities that can detect movement 15 miles away as they fly over vast stretches of cactus, mesquite and scrub-covered deserts, mountains and sprawling grasslands.

The aircraft, which Israel uses to patrol its frontiers, will be able to read a license plate, view a vehicle’s occupants, even detect weapons, officials said.

“We’re looking to make a determination: Has an incursion occurred? Do we need to respond? And if we do need to respond, we just need information as to how our officers can respond safely,” said David Aguilar. Currently chief of its Tucson sector, Aguilar takes over as national Border Patrol chief on July 1.

Countless hours are squandered sending agents to check tripped border sensors and find and rescue migrants stranded in the wilderness, where scores of illegal crossers die from heat and dehydration each year.

The drones weigh almost 1,000 pounds, have a 35-foot wingspan and can fly faster than 100 mph. They will patrol at 12,000 to 15,000 feet — while being able to swoop in close when necessary, Aguilar said. Pilots on the ground will remotely control them unless the flight is preprogrammed, with another agent interpreting the images and using global positioning to send agents to respond by ground or air.

The Hermes 450s join a number of unmanned aerial vehicles being used domestically. Remote-controlled planes help gather data for environmental studies and patrol Western skies on wildfire watch. In Alaska, the Coast Guard is also testing a drone this summer for fisheries patrols and other uses.

The two Hermes 450s are a key element of the Department of Homeland Security’s efforts to achieve “operational control” of the border. Their $4 million mission ends Sept. 30, when it will be assessed to determine the future of drones with the Border Patrol.

Currently, about 2,300 Border Patrol agents work in Arizona. With less than four months left in the fiscal year that began Oct. 1, the patrol’s Tucson and Yuma sectors (the latter stretching into part of California) have caught 399,642 illegal immigrants.