Beijing has used drones to conduct health monitoring of pine trees in the city's northwest Yanqing district, according to Beijing Evening News on Tuesday.

The 90 cm long drone can fly about one and a half hours before needing to recharge and can cover more than nine square kilometers. In addition, the sensor on the drone has 42 million pixels, said the newspaper.

The drones can automatically capture one partial image every 100 meters. Then hundreds of aerial images generate a remote sensing image which can clearly recognize the suspected areas with pests.

Pinewood nematode disease is considered cancer for trees, said the newspaper. The trees could die within 40 days of being infected by the disease.

Having a 1,060 square kilometers pine trees forest, the city previously monitored pests by field patrol conducted by ecological managers and forest rangers in most mountain forests. Therefore, it was hard to have timely and comprehensive monitoring.