A special freephone number, dubbed "Crimestoppers", has received 50 tip-offs this summer by Northlanders wanting to dob in dope growers.
Northland police say public information left on Crimestoppers has helped them weed out numerous cannabis plots and arrest growers and sellers in the drug world.
Crimestoppers' guarantee of anonymity makes it easy for people who may not feel comfortable talking to police directly to pass on what they know about crimes and the illegal drug trade in the region.
Northland Detective Sergeant John Miller, who runs the annual blitz on drugs, said there had been 50 phonecalls to the line - run by an independent organisation - with excellent information on illegal drug growing in the region this summer.
As a result there had been 38 cases where police could carry out search warrants and there had been numerous arrests and cannabis plants destroyed.
The remaining 12 calls were still being investigated.
"The message is getting through and people are using the line because it's a good set up and remains anonymous," Mr Miller said.
"This information left on the line is being acted on and we will follow up. We want people to continue leaving great information."
He said with indoor growing operations cannabis growers were able to operate all year round.
Harvesting would also be happening over the coming month so there would still be plenty of suspicious activity.
Frequent trips into the bush or rural areas could be a sign that visitors are tending to drug plots.
Mr Miller said details about who was involved, where they lived, what vehicles they drove and the location of the drugs were crucial pieces of information to leave on the Crimestoppers line.
Since October 2009, information from Crimestoppers had been responsible for, or contributed to, nearly 700 charges being laid against 250 people nationally.
Northland police are still urging people to report suspicious behaviour that could be connected to illegal drug growing over the next few months.
To contact Crimestoppers, call 0800 555 111 or go to www.crimestoppers-nz.org and use the secure web form.