It is warning when the locusts become adults the swarms could cover an area up to 5000 hectares.

The DPI believes swarms of locusts will next week move south-east and south-west out of the Mitiamo area, in central north Victoria, while other swarms could cross the border from New South Wales.

"Swarms are expected to move into more densely populated areas starting next week," the DPI said.

"They will cross roads and may enter towns."

Agriculture Minister Bob Cameron has said it was "probable" some swarms would get as far south as Melbourne over the summer.

The DPI is spraying an area covering 300 square kilometres, including private land, in an effort to stop the locusts.

Densely settled and farmed areas cannot be sprayed.

Weather conditions had prevented recent spraying, but the aerial attacks would continue until Friday as long as conditions remained suitable, the DPI said.

"This illustrates the difficulties that weather has created for aerial spraying of locusts in both southern NSW and north central Victoria since early October," the DPI said.

But the State Opposition today said the Government had waited too long before deciding to spray private land.

"The Bracks Government's slow reaction to the locust threat has resulted in plagues severely affecting thousands of hectares of farmland throughout Victoria," Opposition agriculture spokesman Philip Davis said.

"Attempting to control these locusts now will be a real battle. For any action to be effective, the DPI should have sprayed all land in the region before the locusts began to swarm."

Source