The low to medium density locust swarm is the largest in the area and is located across 15 kilometres between the Macquarie River and Kickabil Creek, according to Central West Local Land Services (LLS) team leader Lisa Thomas.

The location of the locust swarm is not a surprise to local authorities and landholders as it is known as a traditional area for high concentrations of the insects to migrate.

"We just had a teleconference this morning (Monday) and we have a good handle on where they are moving," she said.

"During our next round of the campaign we need everyone monitoring so we have staff in the right areas."

The Central West LLS have been advising landholders to sow their winter crops at a later date to avoid locust activity.

"Our biggest concern is the impact they will have on winter cereals," Ms Thomas said.

"We have seen before that crops are eaten out and people have had to resow."

Locust activity has also been located close to lucerne crops near Coonabarabran, where two swarms are being monitored by landholders and the Central West LLS.

"They are gravitating to where the good feed is," Ms Thomas said.

The location of the locust swarm north of Dubbo is presenting challenges to the Central West LLS and landholders as spraying is not permitted near waterways to prevent chemical run off.

"When we have campaigns under way there are restrictions to where we can use chemical," Ms Thomas said.

Monitoring is a vital part of the Central West LLS campaign, which relies on landholders reporting locust activity.

Ms Thomas encouraged landholders to report locust activity such as the movement of swarms, banding and hatching, and the laying of eggs.