LOCUST levels in the upper Hunter have become a medium-density incursion, according to Hunter Local Land Services.
The rural authority is working with landholders after recent rain that gave farmers a modicum of relief also created perfect breeding conditions for the Biblical pests.
Chemical control is underway on 16 properties where landholders have notified Hunter Local Land services of Australian plague locusts banding, or gathering together to feed on the ground before they fly to a nesting location.
Invasive species team leader Luke Booth said farmers needed to watch their properties closely for signs of locusts.
"When they are banding, this is the only stage where these locusts can be sprayed, as once they are on the wing, it is too late," Mr Booth said. "We can supply landholders with chemicals to control banding locusts, and are already working with a number of property owners right now."
"If you suspect locusts are banding on your property, it is important you get in touch with your nearest biosecurity officer as soon as possible.
Hundreds of reported sightings in the Hunter began in summer, helping authorities map their movement in the region.
Locust eggs are often laid in bare soil during the autumn eggs, often on clay pans or hard ground near tracks and fences.
Adult plague locusts stand out from other species due to a large dark spot on the tip of their hind wings. They also have distinctive scarlet hind leg sharks and a body colour of grey, brown or green.
They are between 25mm and 42mm long, with females substantially larger than males.
Suspected sightings can be made to 1300 795 299.