NINE planes are on standby to treat swarms of locusts sweeping across drought-affected areas in south-western NSW.

Primary Industries Minister Ian Macdonald says there's no need to panic but the planes will take to the air if the swarms grow larger or thicker.

He says a low-density swarm in the Condobolin district measures about six kilometres long and 170 metres wide.

Low to medium density swarms have also been spotted around Wagga, Gundagai and Narrandera.