Locusts on the wing have been spotted in swarms at Condobolin, Gundagai, Narrandera and Wagga, while a low density swarm about six kilometres long and 170 metres wide has been reported in the Condobolin Rural Lands Protection Board (RLPB) district.

NSW Primary Industries Minister Ian Macdonald said the aircraft were currently on standby to treat swarms as they became "viable targets".

"At this point in time there are no targets that can be treated, but we are monitoring the situation," Mr Macdonald said.

"It's important to realise that most of the State's crops are in the final stages of maturity and close to harvest, so are brown in colour.

"Fortunately this means they are not as attractive to locusts, which prefer green plants, for example irrigated lucernce crops."

The NSW Government, RLPB and NSW Farmers Association control program has so far:

• established a State Locust Control Centre in Orange, as well as regional and local forward command posts at Wagga, Narrandera and Forbes;

• provided specialist training for around 300 staff;

• co-ordinated daily fixed wing and helicopter aerial surveillance at Young, Wagga, Forbes, Ganmain, Gundagai, Condobolin, Coolamon and the Central Tablelands;

• dispatched enough chemical direct to farmers to treat more than 90,000 hectares of locust bands on hundreds of properties and more chemicals are on standby;

• mustered fix wing aircraft and placed on standby for aerial treatment;

• established stocks of Green Guard, a fungal bio-control agent that can be used in environmentally sensitive areas and organic properties; and

• conducted meetings with landholders and a public information blitz across the media.

Mr Macdonald said swarming locusts were expected, even though many immature locusts have already been wiped out before they grew wings.

"The control campaign has been highly successful, with enough insecticide to treat more than 90,000 hectares being distributed and surveillance confirming that most locust bands have been found," he said.

"More swarms are expected over the coming weeks, but fortunately we do not expect swarms on the scale of the 2004 outbreak."

Wet weather may delay any aerial treatment.

Farmers should report locust swarms to their local RLPB.